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Question Antennas, rotators, boosters/preamps... for wide-band VHF/UHF ( AVS Forum HDTV Technical )
Updated: 2008-05-23 09:32:46 (1192)
Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Gathered up some recommended antennas, boosters, etc... for OTA HDTV reception:

Antennas
A-Tech custom assembly - w/ 2 Blake JBX21WB high gain yagi UHF antennas
ATF-X300 Precision Antenna - horizontal dual yagi array
Antiference XG16EW - horizontal dual yagi array
Blake JBX21WB high gain yagi UHF (Blake UK)
Blake JBX21WB high gain yagi UHF (Blake UK)
Blonder Tongue BTY Series VHF & UHF antennas 9/1/05
Antennas Direct 91XG Uni-Directional Antenna - yagi UHF
Televes DAT75 Digital Wideband Tv Aerial - yagi UHF
Triax Unix 100 element aerial - yagi UHF
Antiference DX8W - yagi UHF
Winegard PR-9032 yagi UHF
Channel Master Model 4248 aka 3023 yagi UHF
Winegard HD-9095P yagi UHF
Funke DC.4591-21/69 yagi UHF
Home page for Funke aerial antennas

Channel Master CM 4228 - 8-bay bowtie UHF
Antennas Direct DB2 - 2-bay double bowtie indoor UHF
Antennas Direct DB4 - 4-bay bowtie UHF
Antennas Direct DB8 - 8-bay bowtie UHF
Pro Brand International - 2-bay double bowtie indoor UHF
Radio Shack UHF Dual HDTV Indoor Antenna - 2-bay double bowtie indoor UHF
Winegard Square Shooter (SS-1000 & SS-2000) - indoor/outdoor UHF
Antiference/Zenith Silver Sensor - indoor UHF
Kathrein Scala PR-TV Paraflector parabolic UHF 8/15/06
Wade 4' parabolic UHF antenna 4/12/07
Wade 6' parabolic UHF antenna 4/12/07
Wade 8' parabolic UHF antenna 4/12/07

Rotors, tilters...
ATF-V300 Precision Tilter
ATF-V200 Economy Tilter (use w/Channel Master 9521A rotator)
Channel Master Model 9521A horizontal rotator
ARS Antenna Rotator System for PC
Eagle Aspen ROTR100 rotor 4/12/07
Eagle Aspen ROTR100 rotor test 5/12/07
hy-gain rotators
Yaesu rotators

Preamplifiers/boosters
Angle Linear PHEMT single stage preamplifier - to 20 dB, .4 dB noise
Research Communications Type 9250 HDTV PHEMT LNA - 20 dB, .4 dB noise
Research Communications Type 9248 TV LNA (75 ohms) - 20 dB, .4 dB noise
Winegard AP-4700 UHF Pre-amplifier - 19 dB, 2.9 dB noise
Winegard AP-8275 UHF Pre-amplifier - VHF 28 db, 2.8 noise UHF 29 dB, 2.9 dB noise
Channel Master CM-7775 preamp - 26 dB, 2.0 dB noise
Channel Master CM-7777 preamp - VHF 23 db, 2.8 noise UHF 26 dB, 2.0 dB noise
Kuhne Electronic broadband UHF PHEMT preamplifier - 20 dB, 1.2-2 dB noise
Sitco PA24 Series UHF preamplifier - 25 dB, 1.4 dB noise
Radio Shack 15-2507 - 15 dB each main amp & preamp, <4.5 dB noise

Accessories hyperlinked 6/10/05
Blake non-penetrating roof mount
Antenna mount, side wall installation
CC-5C Multi-conductor control cable
Dual Antenna Boom Assembly
CB-V300 center boom bracket
PH-30B Phasing harness
Winegard CS-002 5-1000MHz Splitter
Antenna Phasing Harnesses and Signal Combiners
CA-11Q - cable type "F" male cable connectors
Channel Master Model 1612 - mast 2 - 1.25" x 10' 16 gauge steel mast tubes
Channel Master CM 9014, 9039 Universal Swivel, Steel Base Mounts & hardware

Antenna/reception links
?How to? for television stations wihin the given range of your location
See broadcast television stations wihin the given range of your location
Latitude/longitude finder
Magnetic declination - values of time/date/locaton...
Antennaweb - finding local TV statios/support
TitanTV
DTV Stations on the Air - state map selection
Worldwide list of Radio & TV Stations 6/9/05
HDTV Television Channel Broadcast Status 6/9/05
National and Worldwide lists of Broadcast Radio, TV and Ham radio stations 6/9/05
same site as above - listing California 6/9/05
Very useful site, w/Doug Lung's weekly RF REPORT column on DTV Technology 6/9/05
No more hit-or miss: spectrum analyzers 9/5/05
The Official AVS Antenna / OTA Reception Topic! 9/6/05
Calculators, maps...
Antenna Up/Down Tilt Calculator (compensates for Earth curvature) 6/9/05
Antenna Tilt Angle Calculator 6/9/05
Interactive Wireless Network Design Analysis Utilities 6/9/05
Antenna - K-Factor & climate effects 6/9/05
Vincenty formula for distance between two Latitude/Longitude points 6/12/05
Vincenty's Formulae, Inverse Method 6/14/05
Forward Inverse - Azimuth, distance... ellipsoidal calc program 6/14/05
Ellipsoid Radii Calculator 6/14/05
Vincenty Ellipsoid corrected ?Great Circle Calculator? 6/14/05
Distance and bearing between two Latitude/Longitude points 6/14/05
Freeware DOS program calculates ellipsoidal geodesic path 6/14/05
UHF conversion charts (channel/frequency) - CATV - TV - FM Frequencies
TerraServer.com - motherload of topo & other maps (hi-rez viewing requires subscription) 6/9/05
GeoCode Eagle will show your GPS LAT/LONG on a Topo Map 6/9/05
Tailor coordinates to yield Topo or Aerial Photo Map in jpg format 6/9/05
Free RADIO MOBILE Propagation Prediction Program, holl_and's thread/description... 6/9/05
Custom topographic maps - free preview 6/8/05
Digital Topo Maps 6/8/05
USGS Maps 6/8/05
TopoZone 6/8/05
SatCalc - pointing angle for any geosynchronous TV satellite 6/8/05
Antenna information
Recommended high gain UHF TV antennas
Fox55 antenna selection
TV and FM receivers, currently used by Dxers
TV and FM receivers, currently used by Dxers
Erecting a TV Antenna & other HDTV Primer links 6/7/05
Indoor antennas
Comparing the common antenna types
Comparing the common antenna types
HEAVY METAL, PART 1 - VHF-UHF Antennas Compared for Outdoor DTV Reception
HEAVY METAL, PART 1 - w/pictures
HEAVY METAL, PART 2 - Comparisons of indoor antennas for VHF-UHF DTV reception 6/7/05
LUXORION - LOTS of Antenna systems info (links on lower page) 6/10/05
FM Antenna Gain and Pattern simulations 6/7/05
Measured Gain for UHF antennas mounted outdoors & in (high loss) attic 6/7/05
Excel spreadsheet comparing manufacturer's Gain, Front/Back Ratio & Beamwidth 6/7/05
measured Gain and VSWR for popular indoor & outdoor UHF antennas 6/7/05
measured Gain and VSWR for popular indoor & outdoor UHF antennas (.xls file) 6/8/05
Antenna VSWR Degradation to DTV Receiver Sensitivity 6/7/05
highest performing Indoor antenna - DB-2 from Antennasdirect (UHF only)
Antenna performance chart
Antenna performance page
Antenna wiring, receiver/transmission noise
Antenna basics - excellent source for technical antenna & accessories info 7/28/05
Diagram of a Half-Wave Coaxial Balun & a handy calculator 6/28/05
On-air DTV test with various length Coax Baluns 7/28/05
Entry point to purchase custom made Coax Baluns ($40) 7/28/05
Winegard transformers 7/28/05
Half-Wave Balun compared to wider bandwidth, low loss, Log Periodic Balun 7/28/05
Some basic Ferrite Balun design information 7/28/05
Maximixe performance of reception antenna installation 7/28/05
Feeder radiation - installing a 1/2 wave coaxial transformer or choke balun 6/27/05
Baluns & Centre Connectors (Balanced/dipole antenna to Unbalanced Circuits) 6/28/05
Other antenna sites
DX FM site
Channel Master reference chart
Stacked Blake Aerials for Digital Television
Televes Dat75
Maxus Super UHF Corner Reflector Yagi MXU59 - yagi deep fringe
Great antenna selection (European models included...)
Stacking TV antennas
A 16-Bay (bowtie) UHF Ant - 2 ChannelMasters or Winegards...
Vertical stacked yagis - Coyote Ranch
Moonbounce (EME) UHF TVDX
Yagi DX antenna arrays
Extra long yagis
Amplifiers, preamplifiers & DTV info
Digital TV Signal Distortion & Interference 9/10/05
High Dynamic Range Receiver Parameters 9/10/05
- RF, RFIC & Microwave Theory, Design RF... amplifier design & theory 9/10/05
Choosing the right antenna preamplifier
Special Frequency GaAsFET Preamplifiers
Angle Linear - pricing & ordering information
Johansson UHF preamplifiers
Johansson UHF preamplifiers
Build An E-pHEMT Low-Noise Amplifier
Micrin 3-channel E-pHMET preamplifier
STB's - Over The Air DTV/HDTV/Cable HDTV In The Clear - QAM
8-VSB, COFDM & DVB-T...
WHAT EXACTLY IS 8-VSB ANYWAY? (suitable OTA MPEG-II encoding and 8-VSB modulation)
Earth's shape & latitude/longitude corrdinates
Earth's gravity definition - the Geoid 6/9/05
Mean Sea Level, GPS, and the Geoid 6/9/05
The Ellipsoid! Or is it the Spheroid? How About Geoid? 6/9/05
Mathworld - Equation 22, finding earth radius @ latitude (for oblate ellipsoid) 6/9/05
The NGS GEOID Page - +/- adjustments for earth's oblate ellipse 6/9/05
NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEIGHT 6/9/05
NSG COMPUTATION OF GEOID03 GEOID HEIGHT 6/9/05
Earth - ellipse demo 6/9/05
The Earth's Geoid 6/9/05
Earth - parametric latitude, WSG84 spheroid specs... 6/9/05
The Earth as an Ellipsoid, flattening, Datum history... 6/9/05

Recommended from fellow AVS Members, other web sites & DX sites (who use enhanced tropospheric propagation to receive signals up to & over 1,000 miles distant). I try to keep separated different antenna types & categories for different uses/needs... Any other models to recommend or those listed to comment on?

Special thanks to AVS Member holl_ands, Wendell R. Breland & videobruce for additions & updates.

Answers: Antennas, rotators, boosters/preamps... for wide-band VHF/UHF ( AVS Forum HDTV Technical )
Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I have an extra D*** Network dish installed on my roof top. Can I use this dish to get HDTV local signals?? Any specific thread on this questions on AVSFORUM?? I am waiting for Sammy 6168 and planning to watch local HDTV through its built in tuner??

gondalguru

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Basically, the "nice" baluns, meaning the ones that are typically 3/4" in diameter, are probably all dual wind transformers and lose in the neighborhood of 1/2dB. The smaller, cheaper baluns, often called "indoor" and about 1/2" in diameter, are single-wind autoformers whose performance varies wildly over the UHF band. A few years ago, a physics professor who was briefly a member here tested one of those autoformers and found that its impedance over the UHF band varied from about 1dB to about 7dB.

I'm pretty sure that the Radio Shack balun made for connecting a 300 ohm twin-lead via screw terminals, to a rear chassis 75 ohm input is a reasonably well engineered balun, but its "F" connection is a push connector, so it may be impractical to make is mechanically reliable and weatherproof if used outdoors.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

FYI: Most 4:1 Coaxial Balun discussions are for Ham radio applications trying to match
a 50 ohm transmitter to a nominal 200 ohm impedance antenna.
A 4:1 Coaxial Balun of the correct length can also be used to match a nominal 300 ohm
UHF antenna to a 75 ohm preamp or downlead cable.

See fol. for a diagram of a Half-Wave Coaxial Balun and a handy Calculator:
http://n-lemma.com/calcs/dipole/balun.htm
Note the default velocity factor (0.66) is for solid polyethelene insulator found in RG-6.

See fol. for on-air DTV test with various length Coax Baluns:
http://www.atechfabrication.com/test...21cd_tests.htm
and entry point to purchase custom made Coax Baluns ($40):
http://www.atechfabrication.com/reception_solutions.htm

Also see fol. Half-Wave Balun compared to wider bandwidth, low loss, Log Periodic Balun:
http://palgong.kyungpook.ac.kr/~ysyoon/Pdf/weif_03.pdf

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

What would be the loss for a coaxial balun best cut to cover the entire UHF band?
Do your simulation results assume a particular antenna....or a perfect 300 ohm source?

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks again Wendell. I'm not too familiar with antenna baluns, but pretty much understand the "electronics"...

I also read from this link on transformer & coax baluns (bottom 1/3 page) the coax balun is more frequency specific & transformer balun is broadband. This transformer balun link Baluns & Centre Connectors (Balanced/dipole antenna to Unbalanced Circuits) seemed to help me see it better...

So I'd assume the coax is a nice cheap way for pulling in lower/difficult channels or a specific "boost" (or noise attenuation) to 1 channel?

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by RayL Jr.
So I'd assume the coax is a nice cheap way for pulling in lower/difficult channels or a specific "boost" (or noise attenuation) to 1 channel?
Ray,

I took a lot of liberty when reference was made to a coaxial balun. It was assumed a DIY would be a technical person.

As to the 1/2λ Coaxial Balun being narrowband, that is correct for the context the author is referring to (Amateur Radio 80 to 10 meter band [~3 to 30 MHz] or ~3.3 octaves). UHF TV channel 14 to 59 is 470 to 740 MHz, that is less than 1 octave. I did a simulation of a 1/2λ coaxial balun in Electronic Workbench and the Bode Plot showed 0 dB of loss at the design channel of 52 (700 MHz), -1.76 dB at channel 14, and -0.05 dB at channel 59. The very best broadband baluns (ferrite core) have an insertion loss of 1.25 to 1.5 dB.

For me: In my area the most desired OTA digital channel is 52, the local CBS affiliate. They have a figure 8 pattern and not much EPR. I am in the null of the pattern and about 20 miles away. I tried to use my old and trusty Channel Master 4 bay bow tie (3021) but could not get reliable reception. Next I tried a Channel Master 4248 and it was no better.

Then I procured a Winegard PR-9032, constructed a 1/2λ coaxial balun and installed. It received channel 52 very well (59 to 65% on MIT MDP-120's). I then installed a Winegard AP-4700 pre amp so that I could install several signal splitters. This has been working very well for 1-1/2 years.

At the time all of this was done I was still employed and had the luxury of a Tektronix RFM151 TV channel signal level meter and analyzer and a Hewlett-Packard spectrum analyzer to test with.

73's
WA5RMP

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks for the info & compliment Wendell! Good suggestion, balanced connections also help in pro audio installs (high power, long multiple runs..), also info from Rane on how balanced/unbalanced works w/transformers. Here's 1 antenna link:

Feeder radiation - installing a 1/2 wave coaxial transformer or choke balun

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by RayL Jr.
Any other models to recommend or those listed to comment on?
Ray, Very nice work.

I would like to point out the Winegard PR-9032 is a top performing UHF antenna and can be purchased for a lot less than the imports.

For the DIY's: If you have low signal levels in your area then construct yourself a 1/2 wave coaxial balun for the very last dB in signal level.

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Cool topic, lots for me to check out before I try some ATSC DXing...

Considering the beamwidth of even high-gain UHF antennas, are you really getting better results by adding "tilt" to terrestrial antenna installations? Seeing the 'less than one degree' remarks above makes me think it is not truly going to accomplish much. (In ham radio, we only use tilt rotation for satellite contacts.)

ChrisW6ATV

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Actually my friend in Buffalo commented "What if an office building is in the way?". Guess it's more acedemic at this point & testing for actual signal strength by rotate & tilt, height, location, obstructions, space... (whether mechanically or physically) is the most accurate way.

Nice to know these calcs can get very precise. BTW, I changed my last equation from spherical cap derivation to finding r1 & r2 radius of earth ellipse (antenna-tower latitudes in radians). Along w/distance to tower it makes a triangle with which I just use the Law of Cosines (knowing 3 sides): CosA=(b^2+c^2-a^2)/(2*b*c). This is direct point but doesn't use K Factor. You can find angles from both transmitter & antenna...

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Well, I played with ellipses & geodesics a lot with speakers/enclosures, domes... & was familiar with the terminology of GPS coordinate conversion, so I dug up some more useful links. Here's the links:

Vincenty formula for distance between two Latitude/Longitude points 6/12/05
Vincenty's Formulae, Inverse Method 6/14/05
Forward Inverse - Azimuth, distance... ellipsoidal calc program 6/14/05
Ellipsoid Radii Calculator 6/14/05
Vincenty Ellipsoid corrected ?Great Circle Calculator? 6/14/05
Distance and bearig between two Latitude/Longitude points 6/14/05
Freeware DOS program calculates ellipsoidal geodesic path 6/14/05

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Slight correction on accurate calcs (edited calc post above) - when you enter say a WGS84 Geodetic lat/long it has to be converted to Geocentric angles on ellipse in math calcs 1st (at the latitude/height correction). Geodetic, geodesic, geographic... references latitudes on a sphere or "Geoid". The Geoid coordinates are an accurate reference for both terrestrial & relative astronomical calcs (also use Geocentric).

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks Ken! Regarding that Antenna Tilt Angle page I had K Factor set @ Infinity. With the default K Factor of 1.33 I got .079 degrees "up" @ 8.5 miles & .025 degrees "down" @ 50 miles. That's within about 1/10th degree of real earth curvature "straight point" adjustment...

K Factor takes into account the effect of the refraction on RF propagation, & varies with climate & location.

I also found these 2 links:

Antenna Up/Down Tilt Calculator (compensates for Earth curvature)
Antenna - K-Factor & climate effects

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Ken H
A tip of the AVS hat to RayL Jr. & holl_ands, for a great topic.
Just noticed it's a sticky after posting... Thanks again Ken H, holl_ands & AVS!

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

A tip of the AVS hat to RayL Jr. & holl_ands, for a great topic.

Ken H

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Again, thanks holl_ands! Just put all those other links in, for now just have some hyperlinks to fill out under Accessories...

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Current worldwide list of Radio & TV Stations, with channel, power, height, lat/long info.
Click on station call letters for map with station location.
http://www.w9wi.com
Not as easy or as quick as www.2150.com/broadcast/default.asp

Yet another list of DTV Stations includes proposed assignment change list:
http://www.tvtower.com/hdtv_status.html

I find the following to be the most comprehensive list of Analog and DTV stations
in Southern California, since it combines all the stations in a particular region into
a single list, eg. LA/Indio/PalmSprings or SD/Baha:
http://www.tvradioworld.com/region1/ca/

National and Worldwide lists of Broadcast Radio, TV and Ham radio stations:
http://www.tvradioworld.com/default.asp

Very useful site, including Doug Lung's weekly RF REPORT column re DTV Technology:
http://www.tvtechnology.com/

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

To find the tilt angle if needed to point antenna ?directly? at tower you can use equation: TAN(a/b)*(180/PI())

a=transmission tower height (Mean Sea Level) minus antenna height (Mean Sea Level)
b=distance to tower from antenna

Just make sure feet, miles, meters... are same units in equations. To adjust antenna heights/tilts angles for earth's curvature, I used a spherical cap formula to find the ?extra height? added relative to reception antenna. This was based on the earth's average radius (3,956.55 miles) assuming it was spherical constant. The diameter of the equator actually exceeds the diameter of poles by about 1/300, but an averaged radius still seems to get within 10th of a degree or so of tilt angle accuracy (about as close as using K Factor of 1.333):

Antenna height gained by earths curvature: 3,956.55-SQRT(3,956.55^2-tower distance miles^2)


***************
The equator is 3,963.19059 miles radius & the poles 3,949.90276... To get a very accurate ?direct point at the tower angle w/earth's curvature? use an oblate ellipsoid of rotation & calculate the angle on a triangle of 3 known sides.

NOTE: 1st obtain & convert Geodetic/Geodesic to Geocentric Latitudes (equation below). Unless you're @ the equator, a Geocentric or ?flattened? latitude will usually be less than given on a map or site unless stated otherwise. Longitude naturally stays the same value (is unaffected by flattening).

New Geocentric latitude(s) in radians: =ATAN((1-(1/298.257223563))*TAN(geodetic or geodesic latitude))

From 2 Geocentric latitudes each radius can be found by using a & b as semi-major & minor axes (earth radius @ point) using Mathworld - Ellipse equation 22:

=SQRT((3,963.19059^2*3,949.90276^2)/(3,963.19059^2*COS(latitude)^2+3,949.90276^2*SIN(latitude)^2 ))

Each latitude location gets it's own radius (2 total). To complete the radius length of each, add the total heights of respective antenna-tower above Mean Sea Level. You can adjust the final radius results with the NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEGHT or NSG COMPUTATION OF GEOID03 GEOID HEIGHT. The last adjustment is usually in only the tens of meters for the Geoid height over/under the ?smooth mathematical? earth ellipsoid...

The 3rd triangle side is the tower-antenna distance. This is derived from the Geocentric latitude/longitude angles & both radii from earth center. No need to find out distances in miles or km, just accurate latitudes/longitudes. This calculates the chord or straight-line distance of 2 points on an ellipsoid. The distance is:

=SQRT((radius1^2+radius2^2)-2*radius1*radius2*(COS(lat1)*COS(lat2)+COS(long1-long2)*SIN(lat1)*SIN(lat2)))

* NOTE: this equation above uses 90 degrees MINUS latitude for lat1 & lat2 for north hemisphere! This is because equation uses Phi/Latitude angle from 0 to 180 degrees starting from ?North Pole? not equator, for south hemisphere it's 90 degrees plus latitude. This is how Phi is actually referenced in polar, spherical... coordinates.

Now with final triangle lengths a,b,c, just use the Law of Cosines to find either or both angles from tower or antenna: ACOS angle =((b^2+c^2-a^2)/(2*b*c)) *(180/pi()) ?a? will always be the side opposite the angle you want (in degrees).

Answer also checks out if you use x,y,z Cartesian values converted from polar coordinates by length= SQRT((x1-x2)^2+(y1-y2)^2+(z1-z2)^2). Things are a lot easier when you have radians & radius equal to 1.
***************


These last adjustments seem to show the 1st result is just a ?hair off?, more so seemingly when tower distances get closer (maybe because it's a spherical cap formula that's distorted slightly, I was looking to adjust to an elliptical cap & other factors got more complex). Since both adjustments are in my spreadsheet (I should get to post) any future calcs won't take much time at all...

So, some interesting related links:

Earth's gravity definition - the Geoid 6/9/05
Mean Sea Level, GPS, and the Geoid 6/9/05
The Ellipsoid! Or is it the Spheroid? How About Geoid? 6/9/05
Mathworld - Equation 22, finding earth radius @ latitude (for oblate ellipsoid) 6/9/05
The NGS GEOID Page - +/- adjustments for earth's oblate ellipse 6/9/05
NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEIGHT 6/9/05
NSG COMPUTATION OF GEOID03 GEOID HEIGHT 6/9/05
Earth - ellipse demo 6/9/05
The Earth's Geoid 6/9/05
Earth - parametric latitude, WSG84 spheroid specs... 6/9/05
The Earth as an Ellipsoid, flattening Datum history... 6/9/05

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks again holl_ands - cool link! I did a spreadsheet calc but can't upload the .xls (Excel) or .sxc (OpenOffice) to my FTP Tripod site right now (AceFTP seems stubborn right now). Funny other same types are there, I must be rusty. Anyway the calcs I have need just 3 parameters (1st 3 numbers):

Antenna tilt angle
Distance to tower (miles) 8.65 45,672.00 (feet)
Height of transmission (from Sea Level) 410.00
Height of antenna (from Sea Level) 1,245.00
Height difference antenna-transmission tower 835.00
Gross tilt angle to point antenna (degrees) 91.05

Earth circumference equator (miles) 24,902.00
Earth circumference poles (miles) 24,860.00
Mean earth diameter (miles) 7,926.55
Mean earth radius (miles) 3,963.28
Net height formed w/earth curvature (miles) .009 49.84 (feet)
Net tilt angle to point antenna (from Theta, 90 degrees level) 91.11

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Satellite Pointing Angle for different satellites:
http://www.nerosoft.com/SatCalcView.asp

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks again holl_ands & again for the compliment. Noted the .xls file link just below the 1st one.

I was also looking at getting my street elevations, etc... correct through topographic maps. Worked so well after printing from the 1st link I feel indebted to order their $15 custom laminated map.

Here's the topo map links added for now:

Custom topographic maps - free preview
Digital Topo Maps
USGS Maps
TopoZone

Wasn't surfing long, so there must be other good ones. 1st link worked just fine for me.

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

The motherload of topo and other maps.
Hi-rez viewing requires subscription. You can also order hi-rez prints for a price.
SEARCH by LAT/LONG, Address, City, Zipcode, etc will reveal over a dozen different
topographic products, including satellite and aerial images:
http://www.terraserver.com/

Punch in street address and GeoCode's Eagle will show your GPS LAT/LONG on a Topo Map:
http://www.geocode.com/modules.php?name=TestDrive_Eagle

Tailor coordinates to yield Topo or Aerial Photo Map in jpg format:
http://www.lostoutdoors.com/newmap.html

I use the free RADIO MOBILE Propagation Prediction Program to view not only very high
resolution topographic maps, but can also use the "MERGE PICTURE" function to display
various images automatically downloaded onto the topo map. This includes road maps
from MAPPOINT/MAPQUEST, LANDSAT IR images, TerraServer images, and Tiger data.
The Topo map data can be either automatically downloaded when you need it, or you
can manually download the much higher resolution (30 m) SRTM-1 database.
See my 22Mar post in the fol thread for RM links and examples:
http://hdtv.forsandiego.com/messages...tml?1112095186

OH, almost forgot...RM also calculates propagation characteristics over irregular terrain.
So you can investigate how much antenna/preamp gain you need.
And did I say that it was FREE???

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

FYI: Kerry Cozad's Gain Summary charts were way too small to read.
See latest update to fol post for Excel Spreadsheets extracted from his presentation,
which are much easier to see now:
http://hdtv.forsandiego.com/messages...tml?1118216319

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

The VHF-UHF ANTENNAS COMPARED FOR OUTDOOR USE is the same as the HEAVY METAL PT1 link, except the latter link has the pretty pictures removed.

HEAVY METAL PT2 (actually lightweight indoor antennas) is at fol link:
http://www.hdtvexpert.com/pages/antin.htm

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks again holl_ands! I'll try to get these links @ bottom more in a relative grouping to keep them better organized...

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks holl_ands! Added & dated those links & gave you credit. Guess I have some more reading to do. Many of these solutions may hopefully be more permanent for the future, unlike a lot of upgrades in the A/V world...

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Well I saw Antennas Direct banner ad here, led me to add a few more excellent antennas...

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Kudos for the very comprehensive antenna reference list.

You might want to add the following to the list:

The www.hdtvprimer.com website isn't logically laid out.
The fol. link should be added to ensure access to additional important links within the site:
http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

FM Antenna Gain and Pattern simulations: http://users.tns.net/~bb/

Bob Chase (Houston Broadcast Engineer) compares measured Gain for numerous
UHF antennas mounted both outdoors and in his (high loss) attic:
http://www.avsforum.com/avs-vb/showt...32#post5410432

I posted an Excel spreadsheet comparing the manufacturer's Gain, Front/Back Ratio and Beamwidth for a couple dozen UHF Antennas and provided comparison to the hdtvprimer NEC Simulation data for several selected antennas:
http://hdtv.forsandiego.com/messages...tml?1109029581

Kerry Kozad (Dielectric) finally posted his paper comparing the measured Gain and VSWR for several of the most popular indoor and outdoor UHF antennas, including a comparison to NEC Simulation results:
https://secure.connect.pbs.org/confe...ns/TC05_43.htm

This is the most comprehensive VSWR measurements effort that I have seen to date,
filling in data for an area the antenna manufacturers woud rather not talk about.
VSWR is important for DTV when an antenna mounted preamp is not used due to
Noise Figure degradation (actually degradation of the DTV signal vectors) as the
signal bounces back and forth on the long downlead.
More on this subject can be found in my fol. post:
http://www.avsforum.com/avs-vb/showt...65#post5399965

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by holl_ands
Back to the drawing board guys....there are over FIVE nearby UHF transmitters with significant levels...
...
If you really want to know how high the receive signal levels are, I suggest you look at the below spread sheet.
Note that I did not calculate the "Add'l Loss" for those towers that are not Line-Of-Sight,
nor the XG-91 antenna pattern as you point towards different stations.
So there is still work for the interested student....
The transmit and receive beampatterns and diffraction losses are important for the low power stations. KTVJ is transmitting in a different direction and all the low power stations are in a completely different receive direction from San Fran so the receive beampattern will be low towards them. The low power stations are also not mounted on high towers so diffraction losses could be significant. All together I don't think the low power stations are a likely overload problem. That leaves KRCB and KTLN as the main overload possibilities. Strong reflected paths from very different angles than the direct path are possible but unlikely so direct path directions are the main threat. The current configuration probably doesn't have severe overload because his performance now for the distance is pretty good- but a slight overload is a possibility. If overload does exist then I would expect any one of the following remedies would likely eliminate it: A horizontal stack with a null towards KRCB plus a Join-Tenna for KTLN if needed, channel 23 and/or channel 68 Join-Tenna's with the unneeded input's terminated, replacing the CM 7777 with a WG 8700 or 4700 or 2870. Note that the horizontal stacking distance is not super critical to eliminate KRCB (ex. 24 inches instead of 22.5 inches should be OK but my original math needs to be checked), just steer to place the null for minimum interference and the main-lobe should be close enough to San Fran. The horizontal stack has the advantage of additional gain as long as a low loss coupler is used. The Winegard pre-amps have the disadvantage of slightly poorer performance than the 7777 in the absence of overload and the Join-Tenna is not well shielded and will add some loss for channels near the "null". One thing that could be tried with the WG pre-amp and Join-Tenna's is to put the Join-Tenna's in the house between the Pre-amp output and a low noise low gain distribution amp. That may help overcome lead-in losses which is especially useful if the receiver has a poor noise figure. I agree though with AntAltMike that once overloading is ruled out there is probably no reasonable way to get a big improvement from the current performance. (edited to add KTLN as an interference possibility)

deconvolver

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by keenan
BTW, all this attention is making me feel like a very important person so I'll say again, I do appreciate all the input, very much.
Nah, just a bunch of bored guys .

Attached is the Digital & Analog stations out to 70 miles Added: for keenan.
.

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by AntAltMike
Which transmitter(s) are you saying are overloading it?

I can't use the linked transmitter locator because I don't have Keenan's map coordinates.
Lat 38.4473457
Lon 122.6992493

BTW, all this attention is making me feel like a very important person so I'll say again, I do appreciate all the input, very much. I look at this as a challenge to try and get the best that is possible.

I'll need to read the last several posts later as I'm off to dinner, but if any additional info from my end is needed, please ask.

Thanks

P.S. If you all feel my particular situation would be better served in another thread and not pollute the focus of this one, please say so.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

The hi-gain CM-7777 is definitely OVERLOADED, and the antenna sidelobes aren't enough to cure the problem,
esp given that signals will also bounce back off nearby hills.

Recommend using a lower gain Preamp, such as the Winegard HDP-269 which has 3 dB Noise Figure,
12 dB Gain (just enough to overcome the coax downlead and HDTV Noise Figure)
and has 11.5 dB HIGHER overload specs that the already excellent W-G AP-4700 (or equal) Preamps.

=======================================================
I did quick Line-Of-Sight check using Google-Earth.
All the nearby stations, except perhaps KTLN are LOS to Keenan's location.
I would guess a moderate amount of "Add'l Loss" due to diffraction from KTLN (under 10 dB?) and Sutro Towers (under 20 dB?).
But if you really want to know, I suggest RADIO MOBILE (for Windows) or SPLAT! (for Linux):
http://hdtv.forsandiego.com/messages...tml?1126050076

Using the exact lat/long from FCC database, you can actually see the towers
or in some cases the ground preparation work since some of the photos are fairly old.
Google-Earth can be off by several minutes from the posted lat/long due to coordinate "datum" differences (FCC's NAD 27 vs WGS84):
http://www.keyhole.com/GoogleEarthHelp/GoogleEarth.htm
[So Keenan is probably not living in a tree house.]

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by holl_ands
....there are over FIVE nearby UHF transmitters with significant levels...

By checking ALL four boxes on the right side of the fol site, you can find ALL of the local transmitters:
http://www.2150.com/broadcast/default.asp
There are two analog UHF transmitters listed only a few miles away (repeater and a so-called "low power"):
UHF CH25: K30DO (aka K25HI), 25.8 deg, 4.7 miles, 17 kW ERP, 17 kW Max, 547 m AMSL.
UHF CH36: KTVJ-LP (Fiori Media), 25.8 deg, 4.7 miles, 21.3 kW ERP, 50 kW Max, 547 m AMSL.
...

Quote:
The hi-gain CM-7777 is definitely OVERLOADED, and the antenna sidelobes aren't enough to cure the problem,
esp given that signals will also bounce back off nearby hills.
Which transmitter(s) are you saying are overloading it?

I wasn't able to use the linked transmitter locator because I don't have Keenan's map coordinates, but I Googled the Santa Rosa, California zip code and determined, via Antenna web, that the Sutro Tower is at a bearing of 145 degrees and the channel 22/23 transmitter is at 108 degrees. The channel 22(23) tower is therefore 37 degrees off targetline. The reception antenna gain of 22/23 will be down by somewhere between 10 and 20dB, most likely, 15dB down or more.

The two local, low-power transmitters that holl_ands has indentifed, at around 25 degrees, are about 120 degrees off-targetline to the rear, meaning the gain of them is down over 20 dB using either the 4228 or the screen-reflected Yagi.

The 7777 has a maximum output of 51dBmV for a two channel load, 47 for four channels and 42 for eight channels. But that refers to equal strength channels. This antenna receives the equivalent of a two or three channel load, maximum. Does anyone remember what a "block tilt" was and is? Blonder Tongue and others used to advise that you could increase your VHF highband channels by 2dB if you also lowered all your low band channels by 4dB. But you only got to do that once. If you instead eliminated the VHF lowband channels all together, you would only raise the highband maximum output by 3dB. But if you then eliminated half the VHF upper channels (not that doing so would ever be beneficial), the maximum output went up by another 3dB

The San Francisco signals are insignificant to the loading estimate. Therefore, this preamp doesn't even begin to excessively intermodulate until the one "pig" carrier output goes somewhere over 50dBmV, which means that its input is over 24dBmV. And even then, that is the level at which an analog picture might begin to show imperfections that initially can only be seen by those who know a TASO Grade 1 picture. The overloading input would have to be several dB higher than that to start breaking up the digital signals.

A low power transmitter five miles away hitting the rear oblique of a screen-reflected antenna will not develop 20dBmv. The only potential threat is the channel 68 that is on line but twenty miles away, and even then, it is not really powerful for that high a frequency, having an output of only 1,000KW.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Given that Keenan already has a tall mast, has already tried one of the best 8 bay bowties and one of the best "yagi(s) with corner reflectors", has a nice, high gain, high powered preamp with little liklihood of amplifier or receiver overload, yet he is generally dissatisfied, across the board, with his distant, San Francisco reception, which, he believes, does not enjoy line-of site predictability, there just isn't any reliable way to improve his reception. He might be better off "borrowing" different receivers and seeing which one seems to most reliably lock onto the signals that he now has.

He can cheaply rule out preamp overload with the trial insertion of 22/47/68 Jointennas. I think I pay $24 each for them. I don't know what retail is, but they will definitively settle the issue of whether he is suffereing from preamp overload fairly cheaply.

He can also buy an analog FSM on eBay for twenty bucks to take out the guesswork regarding the signal strength of undesired signals.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Back to the drawing board guys....there are over FIVE nearby UHF transmitters with significant levels...

By checking ALL four boxes on the right side of the fol site, you can find ALL of the local transmitters:
http://www.2150.com/broadcast/default.asp
Suggest you limit the search radius to about 30 miles, otherwise it times out.

There are two analog UHF transmitters listed only a few miles away (repeater and a so-called "low power"):
UHF CH25: K30DO (aka K25HI), 25.8 deg, 4.7 miles, 17 kW ERP, 17 kW Max, 547 m AMSL.
UHF CH36: KTVJ-LP (Fiori Media), 25.8 deg, 4.7 miles, 21.3 kW ERP, 50 kW Max, 547 m AMSL.

Note that there is an antenna tilt mod for KTVJ-LP listed, reducing ERP (towards horizon) to 21.3 kW,
but the maximum power in all H and V directions is still 50 kW....no doubt directed downwards towards Keenan.

Note KRCB-DT (and KRCB-TV) filed Construction Permits to relocate with different antenna patterns and beam tilt:
UHF CH23, KRCB-DT (Rural), 135/136 deg, 9.5/9.6 miles, 4.7+ kW ERP, 110 kW Max, 800m AMSL.

The downward antenna tilt situation also applies for fol. nearby station:
UHF CH28: KDTV-CA (Sta Rosa), 17.5 deg, 15.1 miles, 8.2 kW ERP, 109 kW Max, 1219 m AMSL.

If you really want to know how high the receive signal levels are, I suggest you look at the below spread sheet.
Note that I did not calculate the "Add'l Loss" for those towers that are not Line-Of-Sight,
nor the XG-91 antenna pattern as you point towards different stations.
So there is still work for the interested student....

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
I alluded to this in Post # 89 by stating what I was using and why. keenan did not seem interested so I did not pursue any further.
It's not that I wasn't interested, I'm just trying trying to absorb all the info presented. I freely admit that a lot of this is over my head. I know see that you gave that info because the towers were close. When I originally read it, I saw the reference to 20 miles and since my desired stations are at 50-60 miles I did not give it the attention it deserved.

I really do appreciate all the info all of you have presented and I'm just trying to consolidate everything down into an approach I should take. My antenna is 70' in the air on top of a tree so trips ups and down need to be at a minimum.

I haven't purchased anything yet so what I do is still on the table. It may very well be that the channel in question is not harming reception of the further located stations and I guess my original query was if steps could be taken to insure that it doesn't.

I think at this point, I will go with dual 91XGs stacked horizontally and spaced as deconvolver suggests, and I'm probably leaning toward the JoinTenna for ch 23.

Would the ability to adjust the horizontal plane remotely be of value? The cost to do such would be around $350. Money is not an issue if the functionality increases at least somewhat. Of course it's impossible to say would it be worth it, I suppose I'm asking simply is it a worthy modification?

I have no line of sight whatsoever to the SF towers, and probably not to the CH 22 tower either, so everything I get is bounced from somewhere.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

As far as Keenan and his Cheshire channel 22.1 are concerned, I have good news and better news. The good news is, according to Antennaweb, channel 23 DTV/22.1 doesn't exist. Even when I punched in Cotati's, California's zip code.

The better news is, the FCC says it does exist but is only transmitting at 67 KW, so there is no way that it is overloading his preamplifier or tuner and should be of no concern to him.

Twenty miles isn't close when a transmitter is 40 degrees off target and transmitting at 67 KW. You should only be thinking about mitigating channels 47 and 68, regardless of what your signal meter scale says. You don't know how strong 68 is because it is analog, and your signal strength indicator saying that 47 is "weaker" than 22.1 is not measuring actual strength, such that it might adversely affect a preamplifier or tuner.

The people here who have installed tilters have enjoyed playing with them, but I don't think anyone vouches for them.

What aren't you getting reliably from San Francisco?

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I pay $19 each for UT-2700s, but you can't buy them where I do. Here is a web page that lists them for under $30:

Winegard UHF TV Antenna Off-Air Signal / Frequency Trap, Variable, Part # UT-2700, UT2700
Item No.: TRPW27
Price: $29.95


And here is someone who lists Blonder Tongue MWT-U Notch Filters for just $111.55, which is about what I would pay to the vendor I would likely buy them from, but I don't know if this company sells retail.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

AntAltMike, thanks for those posts. I'm on my way to the dentist so I don't have time to digest them them yet but I can give you a bit more info. The "signal meter" I'm using is the one in a Dish 942 sat receiver so no doubt it's not entirely accurate for what I need to do. What it tells me is that when tuned to 22.1 or 22.2 the graph style meter is pegged at 100%. I can get a couple of Sutro stations at around 50-65%. The station is KCRB with analog 22 and digital 22.1 and 22.2. And you're right about 47 and 68, they are also strong as well but not as strong as 22.

My actual location is,

Lat 38.4473457
Lon 122.6992493

I don't recall what Sutro Tower or San Bruno Mt transmitters are at but those are the 2 I'm mainly concerned with.

Attached is a PDF map of the transmitter locations in the SF bay area.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by keenan
AntAltMike, thanks for those posts. I'm on my way to the dentist so I don't have time to digest them them yet but I can give you a bit more info. The "signal meter" I'm using is the one in a Dish 942 sat receiver so no doubt it's not entirely accurate for what I need to do. What it tells me is that when tuned to 22.1 or 22.2 the graph style meter is pegged at 100%. I can get a couple of Sutro stations at around 50-65%. The station is KCRB with analog 22 and digital 22.1 and 22.2. And you're right about 47 and 68, they are also strong as well but not as strong as 22.

My actual location is,

Lat 38.4473457
Lon 122.6992493

I don't recall what Sutro Tower or San Bruno Mt transmitters are at but those are the 2 I'm mainly concerned with.

Attached is a PDF map of the transmitter locations in the SF bay area.
Digital receiver graphs don't really show signal strength so you can't tell if KRCB's signal is too strong or not. Some ways to reduce overload are to use a lower gain more overload resistant pre-amp like the Winegard AP-8700 (as long as the receiver doesn't overload) or to use antenna directivity to reduce the interferor. You have 30 degrees between KRCB and the SF towers, with a horizontal stack you could adjust their spacing until KRCB is notched while pointing towards the SF towers. I think that spacing would be at 300/524*(0.5)/sin(30) meters or about 22.5 inches center to center (it's OK if the reflectors overlap a bit). KRCB is at 22 analog and 23 digital (which re-maps to 22.1 & 22.2). So to reduce its power a filter would need to notch both channel's 22 and 23. A Join-Tenna for channel 23 would work and probably only affect channels 19 and 27 slightly if at all. Here is a list of the digital channels near you, note that the reciever will re-map the channel number to the old analog number with -1 or -2 appended etc:
http://www.fcc.gov/fcc-bin/tvq?state...lon2=57&size=9

deconvolver

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by bobchase
...Most of the Winegard amplifiers have the same maximum output level before signal clipping occurs. (Clipping is very bad because it will absolutely kill DTV signal while it just makes NTSC horrible to watch.) So the difference in gain between the various Winegard pre-amps is how much input signal the pre-amp can handle before clipping at the output occurs.

...Another thing that is often overlooked when comparing different brands of amplifiers is how many channels the gain is actually specified for. At UHF, the Winegard specified gain is for 5 TV channels, while Channel Master uses just 2 channels to specify its gain. In Houston we have 32 channels on the air and the pre-amp sees all of them, wether we watch them or not, wether they are analog or digital. Consequently, in Houston, the higher gain pre-amps overload even sooner than the manufacturers specs would have you belive. Also, keep in mind that it only takes one channel to cause the clipping. Just one extra strong channel can cause a pre-amp to wipe out all of the rest of the channels for you.
With most modern amplifiers, each time you double the number of input channels of equal strength, the maximum output level of the preamp goes down by 3dB, so if a preamp can output 51dBmV with a three channel load, then it can only output 48dB with a six channel load.

Some amplifiers of inferior design can't handle large channel loads at all. For example, the popular Tru Spec TA-25's maximum output seems to drop by 8dB or more every time the channel load is doubled. They are therefore absolutely useless as cable TV amplifiers.

I don't think that the problem with preamplifiers, when overloaded, is clipping, as much as it is intermodulation distortion. If clipping were the problem, then the analog channel on which the symptom would first and most severely appear would be the strongest channel, when, in fact, it is the weakest that first suffers.

I know of no way to measure intermodulation distortion, so I just have to accept the manufacturer's specs regarding it on faith, just as I do when I design complex satellite intermediate frequency distribution systems. We try to keep something called Third Order intermodulation distortion developed intermediate frequency satellite signal RF distribution below -40dBc. We do so because the manufacturers of the receivers say to.

Spaun, a major supplier of commercial RF distribution products, rates the maximum output of its products in microvolts, such that their amplification products will not exceed -35dBc in 3rd Order IMD with a one "channel" load, so first, we subtract 108.75 to convert to dBm, then we subtract either 12 or 15 dB depending on whether the load is 16 or 32 transponders, then we derate it by another 2.5dB to further reduce the 3rd Order IMD from -35dBc to -40dBc because for each dB the input goes down, the intermodulation distortion goes down by 2dB. Spaun references their products to -35dBc because that is the benchmark level for analog picture quality, sort of like 46dB S/N ratio is for picture quality.

Then, if there is a second amplifier in cascade with the first, we have to further limit the 3rd order IMD developed at each stage to -46dBc, because it goes up by 6 dB every time we double the number of amplifiers in the cascade.

Broadcast frequency distribution amplifier manufacturers publish specs for Composite Triple Beat, Cross Modulation and Composite Second Order intermodulation. As long as we use only one amplifier, we don't need to concern ourselves with the implications of those ratings, but when we cascade them, we do have to consider them.

As far as I know, the major manuacturers of cable TV RF amplification equipment are still rating their equipment based on the peak signal strength of analog carriers. About three years ago, I spent half a day on the phone talking to the technical service departments of several major manufacturers, trying to get them to estimate what kind of digital, RMS signal levels would develop undesired intermodulation byproducts that would exceed any industry recognized arbitrary standard for their amplifiers. I might as well have been talking to them in Chinese. In fairness to the manufacturers, they surely don't assign the task of answering telephone queries to their design engineers, but it bothers me that I am still "flying in the dark" when I attempt to estimate the maximum loading of my distribution amplifiers that have mixed digital and analog loads.

When I view the "+1" digital channels in my market (45/46, 50/51 and 56/57) on my BTSA-5 spectrum analyzer, I observe that, visually, the digital plateau is about 20dB below the lower adjacent channel visual carrier when I set my spectrum analyzer at a 1Mz bandwidth. Figuring that the bandwidth correction factor would bring the actual, 6Mz value of the digital signal up by about 8dB, I then try to set the rest of the digital channels at the same level or slightly below.

How much do those digital channels further load the amplifier? Beats me! They obviously contain a lot more RF energy than do analog signals of the same nominal voltage level, but I don't know how to combined these unlike terms for calculating amplifier loading.

I typically set up a headend such that the three or four strongest analog channels are at a level such that, if they were the only load present, then the launch amplifier output would still be a few dB below its maximum rated output for that load, and then I add about a dozen digital signals that are 15 to 20dB below that level, and then there are half a dozen additional analog signals at levels about 5 dB or so below the strongest analog signals.

I haven't yet experienced any symptoms of amplifier overloading, which is to say, I have never had a resident's receiver fail to process signals that I could process at the headend, but still, I'd surely like to be able to better calculate my distortion power ceilings because there are some large buildings I design broadcast HDTV headends for existing distribution where I need to deliver every dBmV I can to make sure the signals reach the bottom floor units, but right now, I generally do not exceed levels of about 55dBmV analog and maybe 35dBmV digital at 700Mz. But since these signals are being fed into loop systems that were engineered for 60 to 66dBmV VHF input signals, they sometimes result in grainy analog UHF pictures on the lower floors. If the UHF signal levl drops to, say, -15dBmV analog peak at 700 Mz, then the RMS digital signal level at that point would typically be about -35dBmV. In that situation, the UHF analog looks horrible, but the digital signal strength is still sufficient as long as they don't get piggy and split it, but I need a greater launch level than I feel I can safely develop presently, otherwise I have to keep all of the internal wiring perfect, which is not always practical.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
No, a spectrum analyzer with a tracking generator is needed to do it properly. An O'scope is not the proper device. A good RF signal generator and field strength meter would get you close.

An alternate method: Connect a cable direct to your antenna and a receiving device that has some type of signal level indicator. Tune the undesired channel and peak antenna for max level. Note the signal level. Insert the MWT-U and tune for minimal signal level.
Can this be done downstream from the pre-amp? And then I assume it should be mounted before the pre-amp for final installation?

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Great! Thanks all for the help and info, I'll let you know how it turns out.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

With an MWT-u, Keenan will be swatting a gnat with a sledge hammer, and probably missing it.

His local channel 22 is about forty degrees off his San Francisco transmission path. Unless he has been forced to misaim his antenna because of obstructions, then the signal strength coming off his antenna couldn't possible exceed 30dBmV at that angle and distance, and is surely less than that. So it is either not driving his preamp into to excessive intermodulation distortion, which, with non-adjacent channels, is usually all that we care about, or is barely doing so.

He says that his signal meter is "pegged" on channel 22. What kind of tuner does he have that gives an indication of analog signal strength? Is this really 22 analog, or is there a "22.1" digital that does not show up in the "antennaweb" table generated with Keenan's zip code? And unless it is denominated in dBmV, it is not indicative of an overload condition and gives no cause for concern. Such a primitive meter could peg at a certain S/N ratio safe signal level or some combination thereof, just as similar digital meters reach 100% when error correction is at zero yet the absolute signal strength is anywhere above maybe -50dBm, leaving lots of headroom.

If his tuner really has an analog signal meter, I'd expect it to measure just the visual carrier, which means that using it to primitively tune a notch filter would not suppress the aural carrier, which he may desire to do. To knock channel 22 down for $30 instead of for $190, what he needs to do is buy a Winegard UT-2700 (see post below) and maybe four 10dB attenuator pads. Pad down the line so that the picture is grainy, and then tune one notch to knock out the audio and the other to decimate the video. Then, remove the attenuator pads. The aural carrier of 22 analog is about 7Mz below the ATSC channel 24 pilot (San Francisco ABC), so if channel 22 analog really is 40 to 50dB stronger than channel 24 digital (which is possible), and if the problem is that the undesired channel 22 analog signal is overloading the ATSC tuner when tuning 24-digital (which I'm inclined to doubt), then he would be more concerned with attenuating the channel 22 aural carrier rather than its visual carrier, which is over 11 Mz below the channel 24 ATSC pilot.

The MWT series filters were designed a long time ago to meet certain situations for mitigating interference on analog channels. A BT MWT with both notches tuned to the same carrier attenuates it by some 60dB, but the notch, defined by its 3dB points, is very narrow (I think under 4Mz at UHF frequencies), which is important when one is trying to slightly reduce an aural carrier without degrading the quality of the color burst, but they are of limited usefulness in suppressing digital channels.

I recently had to weaken the unintended. off-axis reception of a distant station in a master antenna DTV reception array. I used an old Channel Master dual, vernier UHF trap. Its notches are no where near as deep as the MWT notches, which, by itself, is not really a problem in most digital applications, since the capture ratio of the desired DTV signal is pretty low. I don't know how low, but it is well under 20dB. Anyway, the dual notch left me with three peaks across the plateau, which meant that, by that one measure, its performance was inferior to what a Jointenna could do for me.

But unfortunately, the Jointenna cases leak like sieves and this installation was less than two miles from another DTV transmitter, so if I used the Jointenna, I would have been leaking in another undesired signal. I therefore stayed with the Channel Master trap. (Note: the UT-2700 also has a plastic case, and invites ingress problems in urban situations). I'm going to have someone custom make a solid channel 45/46 band reject for me, which is not that difficult to construct because that coax only needs to pass channel 39 and below, and channel 50 and above. In fact, I just might order channel 39 low pass and channel 50 high pass "tier traps" to accomplish the same thing.

Keenan also has Univision on his intended target line broadcasting on DT 47 and an analog 68 at a distance of maybe 20 or so miles. I would worry about those more.

With all the money he'll be saving with the Winegard UT-2700, he can buy a channel 68 Jointenna and a channel 47 (or better yet, a channel 49) Jointenna and use them as channel suppression filters. A channel 49 Jointenna will knock his channel 47 down by maybe 10dB, which is as much suppression as he could possibly need, but will leave his channel 45 UPN from San Francisco unscathed. With each Jointenna, put an F-75T terminator on its "single channel input" port and use the other two ports to form the band reject filter. Then, mix and match them with your tuned Winegard channel 22 analog reject filter. There will be eight permutations in all. For each permutation, record the so-called "signal strength" numbers for the San Francisco DTV stations. Unfortunately, these need to be inserted between the antenna and the preamp, since the objective here is to see if reducing any of those inputs reduces the debilitating effect of intermodulation distortion in the preamp. Then, use just the one, two or three of these components that optimizes the San Francisco signal level numbers.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Then that's the one I'll use. I'm assuming a signal generator and 'scope could be used to tune the trap on the bench before mounting?

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
keenan, as deconvolver said earlier, a 1/4λ or 1/2λ stub will not work very well for this application. If anyone is interested I can post the dB loss vs frequency for a stub for channel 21.

Blonder Tongue has a unit that will work, the model is MWT-U. This is pro gear and it will cost you. If you download the spec sheet you can see why.

Dishplace has the lowest price that I have found. You may have better luck.

I use a Winegard PR-9032 UHF antenna (very high gain) with a Winegard AP-4700 pre-amp. This pre-amp was chosen for several reasons Bob Chase has listed above. This combo was explanied in this AVS post. Several of the TV towers are less than 20 miles away.
So performance-wise the MWT unit would be the best bet? Cost-wise the cable CH 71-78 notch filter is probably the least expensive but has a much wider band of suppression? And the CM JoinTenna 21/23 probably in between on cost and performance?

$190 is a bit steep for the MWT, but I'm not opposed to something half that price...OTOH, if the MWT is really the best tool for the job then the MWT will be the I'll get.

I'm using a 91XG from AntennaDirecT with a CM 7775 pre-amp. The towers are 55-65 miles away.

I'm also considering stacking 2 91XGs horizontally for a bit more gain and directionality. Also considering the elevation adjuster like the one shown below.


keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Note: Deleted my post concerning 1/4 wave stub filters as after submitting the post I noticed deconvolver had just posted about the same time with better info(including his post in antenna thread in reception area).

Nitewatchman

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Channel Vision 3205 71-78 "notch" filter wipes out broadcast channels 20-27. I think its depth is around 50dB.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by AntAltMike
Channel Vision 3205 71-78 "notch" filter wipes out broadcast channels 21-27. I think its depth is around 50dB.
That would work, it will wipe out my ABC feed on CH 24 but that's okay. It will also help with a "strong" signal I'm getting from a transmitter further south I don't want as well.

The CM JoinTenna 21/23 I may give a try also if it has a liitle narrower bandwidth cut.

Okay, thanks, I think I know what I need to get, now are these sold by anyone other than the manufacturer? If we're talking $10-20 difference between suppliers then I don't really care, but I would hate to pay double or close to double if I don't have to.

Thanks everyone for your help.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by keenan
Okay, so there is no way to just notch out one channel? If I understand correctly, by using a join-tenna for CH 22, all lose 5 channels on each side of 22 as well?

The quarter wave stub, will that have a narrower notch? And if so, where do you obtain them, or do they need to be custom made....is it something you can buy, or do I need to make it myself?

Thanks
A quarter wave stub is a true notch filter but it will also degrade channels on either side of the notch. A half wave shorted stub is a better solution if you aren't trying to pass VHF on the same line but any of the other solutions is probably better than a stub. I analyzed the VSWR and reflection coefficient of stubs to see how wide a notch they create. I posted the result in the local HDTV info and reception forum's antenna thread:
http://www.avsforum.com/avs-vb/showthread.php?t=381623
The reflection coefficient shows how much signal gets reflected back to the antenna instead of received. Whenever the SWR is six to one or greater a significant amount of signal is lost. I would therefore not recommend a quarter wave open stub and I would try another solution before trying the half wave shorted stub. In fact I have ordered two Join-Tennas for my brother in-law to trap the digital and analog channels from a local PAX affiliate that is blasting him but luckily he doesn't need any stations near the notch.

deconvolver

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

A quarter wave stub is a tuned piece of cable spliced into the antenna feed line. It must be trimmed for the velocity factor of the coax being used which varies somewhat between production runs. You can also use a Channelmaster Join-Tenna (which come pre-adjusted to the desired channel) to notch out strong channels.
http://www.channelmaster.com/Pages/TVS/Passives.htm
The VHF models will affect adjacent channels and the UHF models will affect channels within 5 channels of the one being blocked. You can order Join-Tennas from Warren Electronics. The UHF ones need to be tuned to the selected channel so they take a couple of weeks to get in.
http://www.warrenelectronics.com/Antennas/joiners.htm

deconvolver

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Okay, so there is no way to just notch out one channel? If I understand correctly, by using a join-tenna for CH 22, all lose 5 channels on each side of 22 as well?

The quarter wave stub, will that have a narrower notch? And if so, where do you obtain them, or do they need to be custom made....is it something you can buy, or do I need to make it myself?

Thanks

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

A Channel Master UHF Jointenna will generally significantly weaken two channels above and below the coupled channel, and will slightly weaken the third channel above and below, which may be inconsequential if the signals from the third channel above and below are healthy. So, depending on what channels you are intent on preserving, you might even fare better with a channel 21 or 23 Jointenna.

You can significantly weaken a single channel using a Winegard tunable, dual notch filter (UT-2700), but you will have trouble tuning it without a spectrum analyzer.

Do you need channel 22? The blocking path of a Jointenna is more of a band reject filter than a narrow notch filter, so the rejected channel that passes through it is quite often "viewable", if analog, or processable, if digital, but when you put a genuine, sharp notch filter on an analog or digital waveform, the resultant signal is often unviewable or unprocessable.

Eagle Comtronics and Microwave Filter both make inline filters that will suppress just one channel with unintended attenuation [pretty much confined to one channel above and one below. If you have found some retail dealer who will sell you a such cylindrical, "single channel trap" type cable filters, but if they will only supply them tuned to standard, cable TV frequencies, yet if they are cheap enough, you might buy a channel 73 and 74 filter and see how they do for you.

Someone selling retail makes a band reject filter that wipes out half a dozen channels that includes UHF 22, which is just 2Mz (1/3 channel bandwidth) above cable channel 73, and I think it has about 50dB of maximum depth, versus maybe 20dB for a Jointenna, so if you can find that product (Channel Vision maybe, or Channel Plus), it might meet your needs.

If time permits, I might dork around with a quarter wave stub by sourcing white noise into a coax and looking at the spectrum of the attenuated output, but that sounds more like a Ham radio solution than a broadcast TV solution. I suspect that the notch it creates would be weak and wide, and, unless you did a nice job of designing it, it might act like an antenna and pick up undesired signal.

If a quarter wave stub is what I think it is, then if you want to experiment with your own, buy a BNC "T" adaptor (maybe available at Radio Shack) and three, "F" female-to-BNC male adaptors and use that to do a neat job of tapping into the coax. Then try cutting several different, short pieces of coax to use as stubs.

If I'm doing this right, I think the quarter wavelength of channel 22 propagated through the air is just under 6", and so, figuring that RG-6 often has a velocity factor of .78 and RG-59 around .66, then I think that would make the optimal stub around 4" to 5".

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by milt9
yes it is a notch filter. quarter wave of 516.25 open end will notch out ch 22
milt
Thanks, do you know where I can find such a filter? All I have been able to come up with are CATV channel specific filters, can't seem to locate any channel specific OTA RF filters.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by keenan
Could you elaborate? Is this something like a notch filter? The station which pegs the meter is 22 - 516.25. I have to use the pre-amp to have a prayer of getting the distant(60 mi) SF stations, but CH 22 does not need the pre-amp as the transmitter is only 10-15 mi away. I'm concerned that this signal may overload the pre-amp and cause issues with other signals. Thanks.
yes it is a notch filter. quarter wave of 516.25 open end will notch out ch 22
milt

milt9

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks holl_ands, a lot of info & research! I subtitled the list to make it easier to navigate & added those 3 links you gave:

Amplifiers, preamplifiers & DTV info
Digital TV Signal Distortion & Interference 9/10/05
High Dynamic Range Receiver Parameters 9/10/05
RF, RFIC & Microwave Theory, Design - RF... amplifier design & theory 9/10/05

Also Polaris, the North Star (if anyone's interested on positioning) is slowly moving & it's position changes slightly over the years:

Epoch/year, Right Ascension (h:m), Declination (deg:m)

1900.0 1:22.6 +88.77
1950.0 1:48.8 +89.03
1990.0 2:21.3 +89.22
2000.0 2:31.8 +89.26
2010.0 2:43.6 +89.31
2050.0 3:47.5 +89.46

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

with regard to the local station inline to your sf stations, you can put a quarter wave stub on the frequency of the local station on your antenna lead in.
milt

milt9

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by milt9
with regard to the local station inline to your sf stations, you can put a quarter wave stub on the frequency of the local station on your antenna lead in.
milt
Could you elaborate? Is this something like a notch filter? The station which pegs the meter is 22 - 516.25. I have to use the pre-amp to have a prayer of getting the distant(60 mi) SF stations, but CH 22 does not need the pre-amp as the transmitter is only 10-15 mi away. I'm concerned that this signal may overload the pre-amp and cause issues with other signals. Thanks.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I posted a spread sheet, PREAMP SPECS, which summarizes manufacturer specs along with the few actual measurements that I've found published:
http://hdtv.forsandiego.com/messages...tml?1126050076
I also posted a spread sheet, DTV OVERLOAD CALC, which compares the (spec sheet) performance of several different Preamps, which can be tailored for other locations.

If you are in the Australian Outback, you might be able to use one of the high gain Preamps.
For the rest of us located within 15-30 miles of a tower, start with the lower gain models (and under perhaps 10-15 miles, better to forget it.)
Note that the new Winegard HDP-169 has a 5 dB higher overload spec than the other excellent W-G models.

Intermod products will be generated in a Preamp, even when there are moderate signal levels and strong signals will just make it worse.
These may be located on a frequency that you don't care about or is occupied by a signal that is much stronger than the interference,
in which case it may only be a problem during a signal fade event.
On the other hand, it is also likely to affect the weak signal that was the reason you bought the low noise Preamp for anyway.

The trick is to select a Preamp (and perhaps add a small attenuator on the input)
in order to maximize the SFDR (Spurious Free Dynamic Range):
http://www.tvtechnology.com/features...gital_tv.shtml
http://www.odyseus.nildram.co.uk/Sys.../Linearity.pdf
http://www.wj.com/documents/Tech_Not...dyn_range1.pdf
http://www.wj.com/documents/Tech_Not...dyn_range2.pdf

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

bobchase, thanks for the reply. I should have given some additional info in my previous post.

My location is about 55-60 miles from the transmitter(Sutro Tower-SF) with two large peaks in the landscape as the crow flies so all I'm getting in reflected or bounced signals anyway. I'm currently using a CM7775 with a 91XG yagi style antenna mounted 70' in the air. I swapped out a CM4248 for the 91XG and it seems to have a bit better gain than the CM so that has prompted me to try and tweak out the rest of the system. I have considered horizontally mounting 2 91XGs but I'm not sure how much more gain that will give. Also contemplating using a horizontal plane adjuster as well. Getting expensive, but it's fun, when it works..

One more note, I have a local station inline with my path to the SF tower that will consistently come close to pegging the "signal meter"...you noted that a signal may overload the pre-amp, could this station cause me problems? Will I notice if it is?

Thanks again for the input.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Based on the above referenced notes, could one assume that the Winegard AP-8275 pre-amp is the best available..? Or, would the CM-7775 be just as good because of the lower noise number? Put, simply, what is the highest performance pre-amp available?

BTW, thanks to all who have contributed in this thread, there is a wealth of info here, I'll admit that some of it is beyond me, but a great resource nevertheless.

Thanks.

keenan

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by keenan
Based on the above referenced notes, could one assume that the Winegard AP-8275 pre-amp is the best available..? Or, would the CM-7775 be just as good because of the lower noise number? Put, simply, what is the highest performance pre-amp available?

BTW, thanks to all who have contributed in this thread, there is a wealth of info here, I'll admit that some of it is beyond me, but a great resource nevertheless.

Thanks.
Keenan,

That would depend on what your definition of 'highest performance' was.
Most of the Winegard amplifiers have the same maximum output level before signal clipping occurs. (Clipping is very bad because it will absolutely kill DTV signal while it just makes NTSC horrible to watch.) So the difference in gain between the various Winegard pre-amps is how much input signal the pre-amp can handle before clipping at the output occurs.

So if you lived in a town in the middle of nowhere, where all of the NTSC channels were very snowy, maybe the AP8275 or the more popular AP8780 would be just your cup of tea. On the other hand, if you lived fairly close to the transmitter and were using the pre-amp to overcome the losses of your attic (antenna in the attic scenario), the lower gain AP8700 would be a more appropriate pre-amp.

Another thing that is often overlooked when comparing different brands of amplifiers is how many channels the gain is actually specified for. At UHF, the Winegard specified gain is for 5 TV channels, while Channel Master uses just 2 channels to specify its gain. In Houston we have 32 channels on the air and the pre-amp sees all of them, wether we watch them or not, wether they are analog or digital. Consequently, in Houston, the higher gain pre-amps overload even sooner than the manufacturers specs would have you belive. Also, keep in mind that it only takes one channel to cause the clipping. Just one extra strong channel can cause a pre-amp to wipe out all of the rest of the channels for you.

For the most part, a couple of tenths a dB difference in Noise Figure (NF) can be ignored. (And again, you have to know the manufacturers method of determining it before you can start splitting dBs.) However, the difference between a 7 dB and a 3 dB NF is significant. Pre-amps tend to have a 3 dB or less NF while line amps (distribution amps) tend to be up in the 5, 6, or 7 dB NF range. I know there are folks that will disagree with me on this one but the truth is, if you live inside of 60 miles from the transmitter and the NF is less than 3 dB, don't kill yourself trying to get a lower number.

You'll find the Channel Master 7777 a very popular pre-amplifier on this forum. It performs well in the field and in many different locations and situations. It doesn't overload 'too' easily. The VHF and UHF inputs can be split for combining two antennas. The CM7775 has one flaw in that it will not pass VHF like a Winegard AP4700 will. If your area has a broadcaster that is going to go back to VHF after the NTSC kill date, then the 7775 is going to present a problem for you.

The Winegard pre-amps are less popular here but not necessarily because of any performance issues. The Winegard amps are often harder to find locally, while the CM7777 seems to be available everywhere and can be easily taken back to the store for a refund. Someday, I'll get a hold of an AP8780 and test it against my CM7777, then I would be willing to say which one has the 'highest performance'.

Bob Chase
KHWB-TV

bobchase

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

First check to see if the CATV line into the house is grounded. There should be a grounding block or grounded splitter near where the coax enters the building. That device should have a ground wire attached which is connected to the main building ground at the other end. It should not have its own grounding rod unless that rod is bonded to the main building ground with 6ga or heavier copper wire.

The ground loop isolator most often recommended here is made by Jensen. I don't have personal experience with them.

greywolf

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

This thread has some of the most experienced in the antenna and cable world
and that is why I am posting my question here:

I am looking for a solution to eliminate what I believe is current coming in over
the CATV ground. There is a hum coming from the subwoofer and it disappears
when the CATV connection is removed.

I have tried a ground loop isolator, which did not work.

http://www.partsexpress.com/pe/showd...number=180-075

Any help would be highly appreciated.

Statix

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Does a person need an HD antenna to HD quality reception? Or does a strong UHF and/or VHF antenna accomplish the same result?

vreath

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Their is nothing special about any antenna labled HD. Since the HD channels are in the same bands as the analog channels any good antenna will do. Generally a large antenna will be better than a small one for a given band. If your analog chanels look good especially UHF, you are probably good to go. John

ctdish

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Excellent post Wendell. The North star Polaris is @ Right Ascension 02 : 31 : 50.5 (h:m:s), & Declination +89 : 15 : 51 (deg:m:s) - pretty close.

Those spectrum analyzers seem to be $2100-3000 new, looks like there are deals on used & refurbs. Also the Tektronix RFM151 Signal Scout Cable VRF Analyzer, I guess both brands now owned by Textron.

Oil based enamels for metal are ideal for outdoor durability like the Rust-Oleum. I use same paint, also different colors & spray can:

Rust-Oleum Clean Metal Primer 12 oz spray #7780-830 white, clean metal
Rust-Oleum Clean Metal Primer rust inhibitor 1 quart #7780-504 white, clean metal
Rust-Oleum Rusty Metal Primer rust inhibitor 1 quart #7769-504 white, clean metal
Rust-Oleum Protective Enamel oil-based enamel 1 quart #7779 many colors
Rust-Oleum Professional Enamel oil-based enamel 1 gallon #7779 many colors
Rust-Oleum Gloss Protective Enamel 12 oz spray #7770-830 many colors
Rust-Oleum Gloss Hammered Metal Finish enamel 12 oz spray #7210-830 black, gold, green

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

This post addresses several areas of HDTV reception: Finding True North, ATSC Reception Test Equipment, Satellite Dish Aiming, Paint, Washers and Antenna Pictures. See attached PDF files.

Finding True North
The simple way is to use a good magnetic compass. A suitable compass can be found at your local Wal*Mart in the Sporting Goods section. You will need to account for your Magnetic Declination and that can be computed by NOAA Magnetic Declination site.

The sun can be used to find true north, go to NOAA Weather site, enter your nearest city & state, then select Local Climatology, then select the nearest location to you under the Daily Climate Reports. There should be a section that will list the Sun Rise and Sun Set times. Format three cells in Quattro (or Excel) in 24 hour time mode. Enter Sun Rise as XX:XX:XX and Sun Set as YY:YY:YY. In the third cell enter this equation: (((Sun Set-Sun Rise)/2)+Sun Rise) This will calculate your local ?High Noon?. At this time a vertical (plumb) pole or object will cast a shadow on a level surface (tangent) that points due North. Note: when the sun is close to The Tropic of Cancer the shadows will be short in the USA.

The North Star will also get you close. At night, position yourself so your antenna mast is inline between you and the North Star, now mark a spot at your feet. During daylight you can point your antenna boom to the spot previously marked as your starting reference.

Problematic DTV reception:

There will be situations were receiving DTV stations will be difficult. Without proper test equipment the most one can do is place and aim their antenna by trial & error. In most cases analysis with instruments should show if reception at a particular location will be feasible. At minium, the test unit has to have a spectrum analyzer with sufficient resolution and display to show echo nulls, desired channel flatness and other signal degradation. Unfortunately these instruments are fairly expensive and beyond the reach of many (most) serious hobbyists. Listed below are several devices that are designed to analyze DTV signals. A general purpose Tenma Spectrum Analyzer is included because it is relatively inexpensive for this class of equipment. Please note this unit does not cover all the L-Band frequencies and may not be suitable for common satellite use. The Sencore AT1506 seems to be the most advanced DTV analyzer, but I think it is being phased out of their product line.

DISCLAIMER: I have no experience or affiliation with any of the devices listed below except as noted.

At work we had a Tektronix RFM151 that I used for DTV signal evaluation. It appears to be available from Tempo as the Signal Scout RFM151. This was a fine unit but the operation was not very intuitive.

Tempo Signal Scout RFM151, Sencore AT1506, Sencore SA 1454, Sencore SLM 1456, Leader LF 983 (Has been discontinued??) Tenma 72-6696 1GHz Spectrum Analyzer. Added: BK Precision Model 2630 Spectrum Analyzer and Sencore DTU-234 RF Probe with optional software.

Peter Putmanís comments on DTV reception, spectrum analyzers, and some antenna test. HEAVY METAL, PART I, Spectrum Analyzers. More Antenna Test by Bob Chase using a spectrum analyzer.

The file Coaxial Balun-0001.PDF contains a drawing of resistive pads to convert the 50Ω input and tracking generator output of a spectrum analyzer to 75Ω in and out. A Tapered T Attenuator and a 75Ω, 43dB Symmetrical T Attenuator convert the output of a 0 dBm, 50Ω tracking generator to 0 dBmV, 75Ω. The attenuation of the Tapered T Attenuator was chosen so the value of R2 was 0Ω and therefore eliminated. Most outs will be adjustable in 10 dB steps so you could make the Symmetrical T Pad 13 dB and set the generator to -30 dBm. The resistors should be Dale/Vishay RN60 series or better, the 1Ω could be hard to find and one may have to use a thick film resistor. The input to the analyzer has a single 25Ω resistor added in series with the input. Just add 50.5 dB to the analyzers reading to convert to dBmV, i.e., -63.7 + 50.5 = -13.2 dBmV. The operation of a 1/2λ coaxial and a ferrite transformer balun (set to ideal) is included. The 1/2λ coaxial balun is in purple and the ferrite transformer balun is in green.

Satellite Dish Aiming
Tic Mark Spacing-0001.PDF has degree markers for three common use pipe sizes. When printing this sheet make sure the ?Shrink to Fit? option is not checked. A line that is 6 inches in length is at the top and is your reference, measure to make sure that it is the correct length. I print these on 24lb. paper, cutout the desired marker and attach to my dish pole. I cover them with clear weather proof tape (Frost King), see Antenna-0001.PDF for pictures.

Aim your LNB boom arm due South (those dishes with skew should be set to none or neutral skew), take a common paper clip and straighten one leg and temporally tape it to your dish incline bracket so that it is inline with a tic mark. Make a mark where the dish should be rotated to and rotate the dish so the pointer (paper clip) is at the reference mark you made (i.e., your location requires 213? W, 213-180 = 33? West rotation from due South [clockwise, looking down on the dish]). Set the elevation (and skew if multi satellite dish). If done correctly you should have a signal from the desired satellite(s). Tweak the azimuth and elevation for best signal, the skew should not be changed. For folks with small aperture dishes and using linear LNBs, set the skew of your LNB that corresponds to your location and desired satellite. Folks using an H-H motor mount should have their LNB skew set to 0?.

Satellite Dish Paint and Washers
Rust-Oleum Smoke Gray 7786 [20066 77868] paint is a very close color match to the Winegard and KTI satellite dishes that I have. This paint is very slow drying. To touch-up minor scratches I tighten the cotton of a cotton swab, spray the swab and apply.

To minimized scratching the elevation marking on my satellite dish incline brackets used to adjust the dish elevation I procured 1/4 (≤ 76CM dish) and 5/16 (≥ 1M dish) inch nylon washers and placed between the bracket and flat washers.

Pictures
Antenna-0001.PDF contains four pictures of my satellite dishes and antennas. I live in a condo and have very limited use of space. Upper Left: Winegard DS-3100 for Ku satellite (AMC-3 for PBS HD). KTI for Dish Network at 110? and 119?. Upper Right: Rear view of Winegard DS-3100. All the mounting items were fabricated by me from items available at the local building supply and online. 2-3/8, 16ga. fence post, 1-5/8 (actually 1.66") 17ga. fence post, 3/4 EMT, and treated lumber. The hardware items are: stainless steel, galvanized or Grade 8. Lower Left: Winegard PR-9032 UHF antenna, RCA dish for Dish Network at 61.5?. Lower Right: Closeup of the PR-9032.

09-19-05 Added to analyzer list
10-04-05 Added link to Bob Chase antenna test

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by NightHawk
Good stuff but your notation is confusing. 'j' should always be associated with the total reactance, not the real portion of the complex impedance. That's how it is in most texts.
The intent was to simplify and show the Real (j, x axis) and the Imaginary (i, ?y axis) values of the complex impedance (I know j is not real). Edited to add: You are correct. I should have used R = 272Ω, Xl = 127Ω, or x = 272Ω, y = +127Ω.

Rectangular Z = 272+j127Ω, Polar Z = 300∠25?Ω


And another thing, cut me some slack, I am retired and its been 35 years since college . Was there a song about the J Operator or was that Smooth Operator??

PS: NightHawk, are you seeing the Greek symbols?? Some did not show in your Quote Back.

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Yes, I'm seeing the Greek.
In math texts they use i for the orthagonal axis but it was changed to j for electronics texts to avoid confusion with the symbol for instantaneous current. The two should never used in the same equation. Feeling younger yet?

NightHawk

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
are you seeing the Greek symbols??
Symbols? Heck, it's ALL Greek to me.

(Ok, maybe not all of it. But it's been 25 years since I tested for my ham ticket)

Sorry. Couldn't resist.
Doc

DrDon

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
In response to Post Number 58

A dipole antenna has the electrical equivalent of a series connected Resistance, Capacitance and Inductance. 272O j, +127O i is the rectangular values of the polar form of Z = 300O ∠25?. v(272? + 127?) = 300, T = ATAN(127/272) and is = to 25?. The plus value for i means it is inductive (if i were negative, then it would be capacitive). Absolutely nothing vague about it!!!!!
Good stuff but your notation is confusing. 'j' should always be associated with the total reactance, not the real portion of the complex impedance. That's how it is in most texts.

NightHawk

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

OK folks a little background on me. I was a Technical Services Supervisor for 34 years for the statewide public broadcasting system. I have retired and have no ties or connections to any type organization, I do own a small home business. As of June 2007 we have purchased common shares of stock in Dolby Labs. I have a Associates Degree in Electronics Technology, FCC First Class License (in the days before it was a box top) and General Class Amateur Radio License. I was a AES Member for over 20 years.

Attached is a picture of several broadcast or receiving items that I was affiliated with or I was directly responsible for: Left ? 300 ft. microwave tower; at the top of the tower are microwave dishes for a 145mb/s payload statewide digital distribution systems. Down the side is a Channel 20 DTV antenna. We went on the air with ATSC Channel 20 in November 1998.

Right Top ? A 10 meter satellite dish and a 8.5 meter steerable satellite dish. The 8.5 meter is for receive and Ku up-linking. We had several other small dishes for various applications.

Bottom Right ? A 15 ft. Rohn tower on top of the penthouse. We had several channel specific Blonder-Tongue (commerical grade) receiving antennas on this tower.

Bottom Center ? Yours truly in Post Audio siting in front of a 96 X 64 Harrison Audio Desk with a Cinema (5.1) Monitor Group. Audio & Video is my true love. I designed and help construct this room and all the loudspeakers (8). I was responsible for most equipment items at the production center and the HD mobile production trailer.

My personal home theater:

ADC Audio Spectrum Analyzer
Crown PS-400 for Sub-Woofer
Crown DC-300 for Front Main Speakers
Da-Lite Da-Snap 52 X 92 (106 Dia) with Audio Vision material screen*
Dish Network 6000 HD Satellite Receiver
Dish Network 811 HD Satellite Receiver
Hafler DH-120 for Two Back Speakers
Hafler DH-120 for Two Side Speakers
Hafler DH-200 for Front Center Speaker
Heathkit IG-1275 Lin/Log Sweep Generator
Heathkit IM-5238 dB Meter
JVC DLA-HX1U HD Video Projector*
JVC HM-DH5U D-VHS Machine
Marantz MKII IR Remote Control
Outlaw Model 970 Processor/Controller/AM-FM Tuner
Panasonic DMP-BD10 Blu-ray Disc Player
Sony TC-RX311 Cassette Recorder
Sony ST-SE370 AM-FM Tuner
Sony DVP-S7000 DVD Player
Tenma 72-6035 Dual Channel CRT Readout Oscilloscope
URC MX-850 Remote Control with MRF-250 RF Base
X-10 Automation
Zektor HDVI5 a DVI ● S/PDIF Switcher/Selector**

HTPC with MIT MDP-120 ATSC Tuner Card/DVI Daughter Card,** Twinhan 102G Satellite Tuner Card, Samsung 710n LCD monitor, Aura Vision Keyboard (back lighted) and Mouse. Specialty Software: True Audio 1/24 Octave Analyzer, SpectraPlus 3.0 1/3 Octave Analyzer, TSReader Transport Stream Analyzer, Generic CADD, Visual CADD, Auto CAD lt, Bass Box and Box Plot Speaker Design, Cool Edit 2000 Audio Editor, Electronic Workbench and Display Mate.

Antennas: Winegard DS-3100 1M Satellite Dish (used for PBS HD), 18 X 24 inch Dish for Dish Network at 110? & 119?, 18" Round Dish for 61.5? for Dish Network. Winegard PR-9032 UHF Antenna and Winegard VHF Hi-Band YA-1713 with a Channel Master 9521 Rotor, and two Channel Master 5656 U/V Antennas in the attic. In storage: Channel Masterís 4408 FM Antenna, 3021 UHF Antenna, 4248 UHF Antenna and a Silver Sensor UHF Antenna.

*Items purchased from Jason Turk right here at A/V Science Inc.
**Items purchased from Digital Connection, a supporter of A/V Science Inc.

All loudspeakers, 19" Equipment Racks, and HTPC were designed and constructed by me. Several of my hardware items is most likely older than many people on this forum.

04-26-2006: Added Winegard YA-1713 Antenna
12-20-2005: Added HM-DH5U D-VHS Machine
11-04-2006: Added Tenma, Outlaw & URC
12-01-2006: Added Zektor HDVI5 DVI ● S/PDIF Switcher
01-07-2007: Added Panasonic DMP-BD10
01-07-2007: Removed: JVC HM-DH3000U D-VHS Machine ● Sony EP9ES Dolby Digital Decoder ● NEC AVX-910 Audio/Video Switcher/Selector ● NEC PLD-910 Dolby Pro-Logic Surround Decoder

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

In response to Post Number 49

A dipole antenna has the electrical equivalent of a series connected Resistance, Capacitance and Inductance. Z = 272+j127Ω is the rectangular values of the polar form of Z = 300∠25?Ω. √(272? + 127?) = 300, Θ = ATAN(127/272) and is = to 25?. The plus value for j means it is inductive (if j were negative, then it would be capacitive). Absolutely nothing vague about it!!!!!

And once again the common 300Ω to 75Ω commercial ferrite balun is a Z of 4:1 or E of 2:1. For an IDEAL balun. If 1V is applied to the 300Ω terminals from a 300Ω source then there will be 0.5V (a drop of 6dB) across the 75Ω terminal when terminated with 75Ω. The source power and the terminated power levels are the same (IDEAL), P = E?/Z. The 4:1, 1/2λ coaxial balun operates the same way, 300Ω to 75Ω. THE DIFFERENCE: a 1/2λ coaxial balun does not have any core IR losses.

The PR-9032 (as most TV antennas and transmissions in the US) is horizontally polarized. Since the E Field is in the H Plane the vertical mast should have little effect on the reception. Most TV antennas I have installed used this form for mechanical mounting.

A search was made for PR-9032 for all AVS Forums, 12 threads were returned. There was only one post that had a negative comment. I know of a few that connected their balun leads to the 300Ω pass thru terminals and posted here their new Channel Master 4248 was no good. I suspect some have done the same with their PR-9032.


In response to Post Number 47

There are only 16 DTV stations in the CONUS that is above Channel 59. There is no channel 66 or 68 on the east coast. Channel 61 is WNET (PBS).


Conclusion:

In certain situations a coaxial balun will help with difficult ATSC channel reception. In most cases it probably will not make any difference in reception. The Winegard PR-9032 is one of the top performing UHF antennas.

To solve for Z and Θ requires only HS level math. A technical person should have answered these questions without any problem. There are no ?single-wind autoformers? baluns, see the schematic I posted. I can only conclude that you are not a technical person and you need to stop trying to pose as one.

07-31-2005 Edited to insert spaces
08-16-2005 Edited to correct notations

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Here is something that I would consider useful to see calculated. If you have an antenna with a 300 ohm dipole and, in a given field, it develops 10dBmV of signal power when its output terminals are impressed upon a 300 ohm load, which is what it "sees" when connected to a ferrite balun, then how much power would be developed if the output of that same 300 ohm source were instead impressed upon a 75 ohm load, which is what we appear to be doing when we use a 1/2 wave balun?

If it is less than when impressed upon a 300 ohm load, then that differential must be subtracted in the transmission link calculation just as the calculated or actual loss through the ferrite baluns is. In other words, hypothetically, if a ferrite balun 300 ohm input is the optimal load and if its insertion loss is 1.5dB, but if the use of a 1/2 wave balun results in the development of 1dB less of power because of the impedance mismatch, then the differential in power and therefore S/N present at the tuner is only 1/2 dB. I'd like to see the order of magnitude of the net power differential between the two different transmission links before I spend any time dealing with awkward 1/2 wave baluns.

Your experience with the PR-9032 over the Channel Master 4248 is just that: your experience. Two or three years ago, there were legions of members here who swore that the Channel Master yagi outperformed the Winegard. I told them that the difference couldn't amount to more than a warm pot of spit, and that I used and still use a lot more Winegard PRs than CMs, because they cost less and I have three Winegard stocking dealers within 30 miles of me. But I never outlasted the Channel Master afficianados

You should further contemplate Winegard's channel 69 plot, and notice that it is asymmetrical, which is consistent with my speculation that the mast causes it, because the mast is off to the side of the boom, and should also consider that the effects of a larger mast could well disrupt channels in the 50s. In attic applications, with no internal onstructins and no mast, the plots would look more like they do in the HDTVPrimer site, and I imagine that a plastic mast extension might make the mast disruption negligible as well.

But don't lose sight of what I said in the post in which I criticized the PR series upper UHF performance. I said it wouldn't likely be redesigned because it already seems to do well up to 700 Mz, which is where the band will end when the transition is over.

(Edited to extinguish flame war)

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I just received a Research Communications 9250 UHF preamp with a specified gain of 20 dB and a noise figure of 0.4 db. As seen here: http://www.researchcomms.com/hdtv.html I have verified the gain here, but it is going to be a while before I connect it to an antenna. If anyone nearby (SE CT or RI) has away to test it let me know. John

ctdish

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I've tried several indoor antenas and so far have not found a better one than what I currently have - an old (6+ years at least) Recoton 350 non-amplified antenna. It has UHF and VHF reception that hands down beats the likes of Radio Shack's 1880 or RCA ANT200 (both amplified).

I now use the Recoton with my Panasonic TH-42PX50U and I get all digital channels in the DC area and a quite decent reception of most analog channels. In contrast, the RadioShack could only get some of the digital and was notably worse on most analog channels - and it worked OK only if the amp was off or close to max... Go figure...

I guess they don't make them like this anymore - if anyone knows a good indoor antenna for a metropolitan area, please post.

Thanks!

kocho

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Does anyone have any experience with the sat dish style ant's like terk TV42 and TV44 that clip onto the dish?

I haven't tried an ant yet to see what kind of reception I get, but I'm guessing it should be pretty decent considering on a good weather day I have line of sight to the broadcast ant's on the Sears and Hancock 20 miles away.

joebar32

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Interesting concept. Looks like a big paper clip bent around the dish:



Seems not as good as say a 2-bay indoor/outdoor antenna, but for stronger or line-of-sight reception areas. Otherwise most reviews (also on the TV50) seems to relegate them to "a piece of junk"... At least from some Terk reviews @ AudioReview.

If you really want/need a streamlined solution & have the bigger dish for the TV42, it might actually work pretty good in your case. If there's a return policy, maybe try it just before some bad weather hits.

Otherwise if you have room for an outdoor 2-bay, you can get a stronger signal or at least are more guaranteed to for about the same price.

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Those among you willing to go to heroic lengths to maximixe the performance of your reception antenna installation may choose to visit HERE.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Thanks to a number of members for the links here mentioned the past few weeks, I'll add & sort these in:

Antenna basics - excellent source for technical antenna & accessories info 7/28/05
On-air DTV test with various length Coax Baluns 7/28/05
Entry point to purchase custom made Coax Baluns ($40) 7/28/05
Winegard transformers 7/28/05
Half-Wave Balun compared to wider bandwidth, low loss, Log Periodic Balun 7/28/05
Some basic Ferrite Balun design information 7/28/05
Maximixe performance of reception antenna installation 7/28/05


If I were that concerned for higher UHF frequencies in my area, Europeans seem to like the Televes DAT-75. I guess to each his/her own area, situation & requirements. I've seen vicious but informative arguments w/the Channel Master 8-bay vs. Winegard & other yagis between what seems to be experienced pros/installers... in other threads/forums. When does one say they've looked @ say Comparing the common antenna types long enough?

AntAltMike's link is interesting on improving reception drawing a big ellipse & finding optimum location. I've designed sealed concrete cast ellipsoid speaker enclosures using Fibonacci cancellation with a lot of help from Cantrell's ellipse formulas in a spreadsheet, mitigating need for 1/2 wave resonance damping material which can also ?muffle? sound. VERY precise & no Calc III needed.

RayL Jr.

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by carltonrice
Given that the vast majority of stations will end up after the digital transition on channels between 7 and 51, I was curious to know if there are antenna manufacturers making new antennas that are tuned specifically for these frequencies?
A channel 7 antenna only needs to be about 30 or so inches wide. Nearly all of the lowband transmitters in the largest metropolitan markets are giving up their lowband assignment. In my market, 2, 4, and 5 will be staying on UHF, whereas 7, 9, 11 and 13 will be moving down. I think you'll see a lot of 7-51 antennas. The booms will be nearly as long as they are now, but they will have much less wind load and will last a lot longer.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Given that the vast majority of stations will end up after the digital transition on channels between 7 and 51, I was curious to know if there are antenna manufacturers making new antennas that are tuned specifically for these frequencies?

carltonrice

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

If I recall correctly, I once installed a Terk, "magic wand" shaped antenna for carltonrice under a rain gutter, which was better suited to function as a rain gutter.

The Winegard PR-9XXX antennas showed really ugly polar plots at the highest frequencies, so they are probably "tuned" as well as they will ever be for channels 14-51. The front-to-back ratio at high frequencies is horrible and its gain is about 4dB less at channel 69 than at channel 50. The polar plots on the HDTVPrimer site look more like what you'd get of you took about one tenth as many polar points and connected them with a French Curve. If they developed those plots with a primitive simulator, I wonder if it took into account the fact that the mast is in front of the dipole in that series of antenna, and has greater disruptive effect on the shorter wavelengths.

There are probably more people here who got better performance by switching from a PR-9032 to a CM4248 than vice versa, but what most of them don't realize is, the antenna that worked better for them was the one that had the more fortuitously located troughs between its side lobes.

By the way, eight of the eleven channels I measured the signal loss on were analogs. And for the other three, who cares if I am measuring peak or RMS? The loss will be the same.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I posted measurements for seven different baluns, incl. the CM3075 Outdoor 3/4" Diameter Balun as fol:
http://hdtv.forsandiego.com/messages/1/2489.html

The CM3075 (from www.outpost.com, i.e. Frys) was the best of the several Outdoor Baluns tested,
but didn't have quite as low a loss as the several cheap indoor baluns tested.

The two different R-S Outdoor Balun models were measured to have significantly higher loss.

Note that since I retired and no longer have ready access to a room full of test equipment,
a non-traditional measurement method was used (dBmV measurements via Cable STB) for back-to-back baluns.

Also note fol. link to another balun test, including a DIY coax balun description:
http://www.kyes.com/antenna/balun.html

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Ray, I apologize that your reference thread has been hijacked.

In this thread I have stated clearly and concisely what materials and equipment were used in reference to UHF ATSC television reception. Mr. Breland has made no assumptions. I asserted that name brand ferrite baluns would have an insertion loss of ~ 1 to 1.5 dB in the UHF band. Links were provided to substantiate this statement. The Tektronix RFM151 has 10 times the resolution of the Leader LF 941 therefore I will not even comment on the values posted above except to say they are meaningless. In addition, the LF 941 is not suitable for DTV channel measurements, the LF 941D should be used. A 1/2λ coaxial balun does not have insertion loss in the design range.

A variant of a resistive 300Ω source: If the source (folded dipole for 9032 and 4248) should be 272Ω j, +127Ω i at the frequency of interest there will be a reduction in signal level of -0.229 dB using a 1/2λ coaxial balun. Under the same conditions a ferrite style balun with an insertion loss of 1.250 dB will have a total signal reduction of -1.556 dB (1.250 + 0.306).


For those that have problems with hum: I have used with success the MCM 33-8700 Ground Insolation Transformer for several years. If you place an order, use Source Code 53108, then click Update. Should be lower pricing.

For the DIYís using 75Ω coax cable: Take two name brand 300Ω to 75Ω baluns, connect one 300Ω lead to the lead of a 150pF disc capacitor (I use disc caps with a 1KV DC rating). Connect the other lead of this disc capacitor to the second baluns 300Ω lead. Repeat these steps for the other 300Ω leads.

I have constructed these using a small aluminum box. The ferrite cores with their windings were removed from the original housing. The twin leads were discarded. The remaining components and the two disc caps were attached to a G10 perf board. A chassis mount F connector was installed at each end of the box. One of the F connectors must be mounted using fiber shoulder washers to isolate it from the box.


A recap: The Winegard Model PR-9032 in conjunction with a 1/2λ coaxial balun provides reliable reception of DTV Channel 52 in my area. Channel Masterís Model 4248 and Model 3021 (with Model 0089 Balun) did not provide reliable reception on this channel. Where DTV reception is concerned, a dB or so at the receiving antenna can mean the difference between reception and no reception.

FWIW: If one would like to analyze the data stream of a DTV signal check out TSReader . It can be used for OTA, Satellite and cable.

07-12-2005 Edited for clarification
07-13-2005 Attached a schematic of a 300Ω to 75Ω Ferrite Balun

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I assume that the 3/4" baluns that I have experimented with in various field applications are dual wind transformers because I have successfully used them to eliminate ground loops, whereas I have always been unsuccessful at eliminating ground loops with the cheaper, 1/2" diameter baluns. I assume, based on that, that the 1/2" baluns are single wind autoformers in which there is a tap connection point such that three-fourths of the windings are on one side of it and one side are on the other side. I have not cut a whole lot of them open.

When you use the term ferrite baluns, are you limiting that to single-wind autoformers with ferrite cores, or might that term also be used to describe devices with dual isolated windings that might also have ferrite cores? I'm certain that the frequency response of the latter will be much flatter than the frequency loss of the former.

Right now, my only spectrum analyzer that has fine enough vertical resolution to meaningfully evaluate fractional dB variations is my disassembled AVCOM (started to fix the battery charger, but never got around to finishing the job) then only way that I could endeavor to test what I have lying around would be to maybe couple four of them together and divide the measured losses by four.

In light of the fact that your calculator had determined that a so-called "coaxial balun" optimized to the UHF band would have insertion losses of -0.69dB at 470 MHz, 0.0dB at 605 MHz (Mid Band) and -0.51dB at 740MHz., I don't see why you would be surprised to hear that someone who had once measured what were believed to be dual wind transformer baluns had losses consistent with the coaxial balun that you have simulated.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

I just cut the fork lugs off two Channel Master 7982 Matching transformers, those being of the indoor, narrow body design that I often derisively refer to as the "cheap ones", twisted the leads together, and measured the signal strengths of eleven cable TV channels, 6 VHF and 5 Hyperband or higher, to measure their insertion loss, using a Leader LF 941 FSM, which regrettably, only has a resolution of 1dB. I then divided the difference by two.

4 (67Mz) no insertion loss
5 (77Mz) 1/2 dB per balun
7 (175Mz) 1dB
9 (187Mz) 1/2dB
11 (199Mz) 1dB
13 (211Mz) 1dB

65 (469Mz) 1/2 dB
75 (529Mz) 1 dB
85 (589Mz) 1dB
110 (709Mz) 1/2dB
120 (769Mz) 1dB

Amazing. I had tested a handful of baluns about ten years ago, when I first moved to the Washington, DC market and began servicing master antenna systems, as some buildings distributed local broadcast channels 20 (507Mz) and 26 (543Mz) on their natural frequencies, so I needed to have some idea of what the hardware I was using was capable of doing at those frequencies. As I have remarked in other threads, I had observed erratic, inconsistent insertion loss performance with the narrow diameter, so-called "indoor" baluns at different frequencies, which also have consistently failed me as ground loop isolators, but I never have had any reason to attempt to replicate the testing that I did.

I'm still inclined to doubt that these Channel Master $.42 baluns, are fairly evenly losing just .7dB on the average in both bands. My test cable signal goes through a two-way hybrid, then a -9dB directional coupler, and the tap port splits again with one leg going to my viewing TV and the other available to my test bench, so it is possible that this double balun somehow stabilizes the load impedance better than does my Leader meter by itself, but that, like so many things in antenna development, is just speculation.

A lot of time is spent at this forum with people speculating on how they MIGHT improve their S/N ratios by a fraction of a dB, but such theoretical improvements so small can easily be offset by other unintended effects. For example, when Mr. Breland calculated the expected losses for his 605Mz coaxial balun, which he reported to the nearest one-hundredth of a dB, he was assuming a perfect 300 ohm source, but the coaxial balun will be used to enable the nominally 300 ohm source to drive a 75 ohm load, which will enjoy less than optimal power transfer efficiency. The inefficiency of driving a 75 ohm load with a 300 ohm source could result in more signal reduction than is gained by minimizing the insertion loss. Maybe it is better to use a preamp with a natural 300 ohm input instead.

I am fortunate in that I do most of my work on high-rise buildings within ten miles of most of the transmitters, so my broadcast DVT antennas naturally develop S/N ratios of 40 to 60dB or more. But those of you who feel a need to scrounge for fractional increases to your own signal levels are commonly 40 miles or more from the transmitters, meaning that your signal goes through some vegetation, and just the rustling of distant leaves will make it go up and down by a few dB even on a clear day. If you have an unreliable signal lock, such that you occasionally experience pixelating or blocking or freezing, the likelihood that a fractional increase in your S/N ratio will notably improve the reliability of your reception link from unacceptable to acceptable is near zilch.

If you want to spend time and money improving your signal reliability, spend it on the antenna, the mast, the preamplifier or the aiming.

AntAltMike

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
Bob Chase

Downloaded your Antenna Test PDF file. Nice piece of work, the effort to test and document such a task is greatly appreciated. Anyone remotely interested in television antennas should download Bobís Antenna Test.

I really like the look of the spectrum data. Was the data imported into Excel and plotted or does the Agilent E4401B generate its own graphs?
The 4401 will generate a low-res pcx file, if you ask it to. What you are seeing is an Excel chart with 4001 data points per band, per antenna. (One 4001 point sweep for the UHF band and another 4001 data point sweep for the VHF band.) Each sweep (U or V) for each antenna has it's own tab within the spreadsheet. That data is displayed in the charts. Each tab also has a look-up function to show the peak NTSC value and the mid-band DTV value of each Houston channel but that data does not show up on these charts.

Bob C

bobchase

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Bob Chase

Downloaded your Antenna Test PDF file. Nice piece of work, the effort to test and document such a task is greatly appreciated. Anyone remotely interested in television antennas should download Bobís Antenna Test.

I really like the look of the spectrum data. Was the data imported into Excel and plotted or does the Agilent E4401B generate its own graphs?

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Sorry to intrude on the subject but this looked like good spot to ask my question. I have just finished setting up a cm4228. I have a signal strengh of 74-89 atthe TV across the five channels that I receive. Can I get good results from a preamp with signal levels as high as these. I'm about 60 miles out from the towers.

Thanks

pnyxxpress

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by holl_ands
Further investigation revealed Peak-to-Average Power Ratios for ATSC and NTSC aren't all that much different:
8-VSB Peak-to-Average Power Ratio is 7 dB +/- 1 dB.
NTSC Peak-to-Average Power Ratio is 5.14 dB for Mid-Gray luminance level,
7.55 dB for Pure White and 2.23 dB for Pure Black. [That's 4.9 dB +/- 2.7 dB]

=====================================================
Fol. provides ATSC Grand Alliance Test Results (mid-90's) for percentage of time exceeded vs Peak-To-Average Power Ratio:
http://www.zenith.com/digitalbroadca...%20Results.pdf
This is in very close agreement with the numbers discussed above (from AUS report).

=====================================================
Fol. from Harris (transmitter manufacturer) provides Visual Carrier Peak-to-Average for analog NTSC-M, PAL, ATSC and DVB-T:
http://www.broadcastpapers.com/tvtra...ansmitters.pdf
These are as summarized above.
I would expect that under color bar test conditions, there would be more energy in the (negative) video signal,
since darker colors are at larger amplitude levels, and hence peak-to-average ratio might be in 3-4 dB region.
By the same argument, "typical" on-air signals would frequently have dark scenes that would approach
2.2 dB Peak-to-Average Ratio (i.e. more average energy for same peak power level).

The FM audio carrier can not be ignored in NTSC overload calculations.
Per Bob Chase's recent on-air tests, the average power appears to vary from 4 to 10 dB below the visual carrier.
The Chroma carrier is much lower and can be ignored.
Holl_ands,
What I haven't published is the CM7777 overload testing I was doing that morning. Although I have no problem sharing, I think I should redo it with two simutaneous sweeps. One in 'Max Hold' and the other in 'Average'. Then you can see the DTV average power vs DTV peak power. It will also capture the NTSC peaks. The off-air tests you reference above were done using a SA in 'View' mode and then averaging 100 samples. Which means that the NTSC power values shown are APL dependent and do not represent the peak power of the station. (APL = Average Picture Level)

NTSC transmitters are set up using average power. This is done by transmitting sync & blanking signals only. (No chroma, setup, or video information and the aural carrier disabled.) A demodulated wavform shows nothing above the 0 IRE scale and only the sync pulses below. The measured average power is multiplied by 1.68 to log the peak power. The aural carrier is then abled and set to where the station wants to run it (typically from 5% to 10% of peak power). The chroma sub-carrier plays a significant part in causing intermodulation products in a NTSC transmitter. However, I would agree that with the amount of carriers presented to a pre-amp in the Houston market, the chroma sub-carriers can be pretty much ignored for overload calculations.

When we setup or size DTV transmitters we use a 6.4 dB factor (that is often rounded down 4x) for peak to average power ratio. But that is based on 10E3 data samples. The tube manufacturer uses similar ratios when rating amplifier tubes. The newest E2V (aka EEV, aka Marconi) 3130 tube is rated at an output of 145 kW peak digital power and 35 kW average power. The same tube is rated at 88 kW NTSC visual only service or 77kW with 10% aural in a common mode amplification transmitter.

Bob Chase
KHWB-TV

bobchase

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by holl_ands
Question for Bob Chase:
In your signal spectra charts, KUHT-TV (N08) had an unusual hump between 180 MHz and
the visual carrier at 181 MHz.

I see that this PBS station does datacasting, which presumably uses 8-VSB packets,
and hence would not cause this hump.

I wondered if you knew whether they might also be using something like the DotCast dNTSC datacasting system
(also used for MovieBeam) that adds a reduced level QAM carrier in quadrature onto the visual carrier?
Holl_ands,
KUHT does indeed DotCast but their chief & I have been playing phone tag. I'll let you know what I find out.

Bob Chase

bobchase

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by holl_ands
I am trying to determine how to extrapolate the published NTSC Preamp specs for use with DTV signals.
Very good and thanks for the links.

I did a simulation in Workbench (using sine waves) of 5 UHF channels at various levels to see what the composite P-P value would be. You may find it interesting.

  1. Channel dBmV In Volts
    CH 20 -12.0 2.51E-04
    CH 22 -17.0 1.41E-04
    CH 35 -22.0 7.94E-05
    CH 40 -8.00 3.98E-04
    CH 52 -24.0 6.31E-05
The composite values: P-P = 2.56mV, RMS = .91mV or +0.87 dBmV

For equal levels
  1. Channel dBmV In Volts
    CH 20 0.00 1.00E-03
    CH 22 0.00 1.00E-03
    CH 35 0.00 1.00E-03
    CH 40 0.00 1.00E-03
    CH 52 0.00 1.00E-03
The composite values: P-P = 11.39mV, RMS = 4.0mV or +12.1 dBmV

Edited 09-30-2005 to correct RMS level
Edited 09-30-2005 to add equal channel levels

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by Wendell R. Breland
For the purpose of pre-amp overload you are using 7 dB between DTV and NTSC stations is that correct? It works for me, but it will be interesting to see the final description of the 0 dBDTV from the IEEE. I could not find Bob Chase's on-air tests, do you have a link?

For station clock (sync) reference: PBS used to use three Cesium Beam clocks averaged together. We had two Grass Valley generators and I used to compare the phase angle (not frequency) between the two in degrees. On the HD production trailer we had a Leitch sync generator that could use the on board GPS receiver as a reference.

For fun: The peak-to-peak value 400 Hz and 1 KHz will remain the same regardless of the phase angle between them. The peak-to-peak value 400 Hz and 800 Hz (or any multiple 2nd, 3rd, etc. of 400) will change depending on their phase differences.
I am trying to determine how to extrapolate the published NTSC Preamp specs for use with DTV signals.
NTSC signals are measured with a peak power meter (actually the average power within the blanking interval,
rather than instantaneous worst case peak voltage).
In order to treat DTV signals equally with NTSC, for a first order estimate, all we need to do is convert DTV's
average power into peak power by adding about 7 dB +/1 dB. [Give or take a few dB.]

If I were concerned about preventing clipping in the Preamp with a single DTV signal,
I might want to allow a little more "head room" to accomodate the infrequent instantaneous peaks.
I would rather not have any erasure errors in the Preamp, since they detract from on-air multipath error resistance.
NTSC would also have some instantaneous peaks, but not as much as DTV and clipping would have little effect

I am still working on how to handle the more complicated multiple signal derating.
The C-M and W-G spec points are for a 46 dB Cross Modulation level.
That means the NTSC (peak) intermod products on the output of the Preamp are 46 dB below the individual (peak) output signals.
The NTSC multiple signal (peak) power backoffs are probably in the same ballpark for DTV (peak) power, however,
the EFFECT of intermod products is quite different for DTV vs NTSC, NTSC vs DTV, DTV vs DTV and NTSC vs NTSC.

========================================================
See bobchase 9/24/05 post in Antenna Thread comparing on-air measurements for 8 antennas:
http://www.avsforum.com/avs-vb/showt...&page=93&pp=30

FYI, also see bobchase 3/28/05 at 8:23pm post comparing outdoor vs attic on-air measurements:
http://www.avsforum.com/avs-vb/showt...&page=58&pp=30
And bobchase 3/30/05 post at 8:31pm showing results for different attic locations:
http://www.avsforum.com/avs-vb/showt...32#post5410432

2. Eons ago, NTSC signals were synchronized to the 60 Hz power grid.
Hence I would expect that all stations in a local area would have transmitted the first pulse in each frame
at almost the exact same time. At the Preamp, this would result in very large spikes.
I don't (yet) know whether there is synchronization of the 59.94 Hz frame rates from station to station.
This would be different than synchronizing to 5 MHz GPS/WWV and/or 60 kHz WWVB:
See "STANDARD" paragraph in fol: http://en.wikipedia.org/wiki/NTSC

holl_ands

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

See my post in your other thread. If you connected to the antenna with the pre-amp on it and didn't power the pre-amp then no signal would get through- a pre-amp blocks signals when not powered. A splitter would typically block the power to the pre-amp unless it had a DC pass through on the connection to the antenna.

deconvolver

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

replying to this post in the other thread as well.

Quote:
Originally Posted by deconvolver
See my post in your other thread. If you connected to the antenna with the pre-amp on it and didn't power the pre-amp then no signal would get through- a pre-amp blocks signals when not powered. A splitter would typically block the power to the pre-amp unless it had a DC pass through on the connection to the antenna.

mallu2u

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by holl_ands
Further investigation revealed Peak-to-Average Power Ratios for ATSC and NTSC aren't all that much different
For the purpose of pre-amp overload you are using 7 dB between DTV and NTSC stations is that correct? It works for me, but it will be interesting to see the final description of the 0 dBDTV from the IEEE. I could not find Bob Chase's on-air tests, do you have a link?

For station clock (sync) reference: PBS used to use three Cesium Beam clocks averaged together. We had two Grass Valley generators and I used to compare the phase angle (not frequency) between the two in degrees. On the HD production trailer we had a Leitch sync generator that could use the on board GPS receiver as a reference.

For fun: The peak-to-peak value 400 Hz and 1 KHz will remain the same regardless of the phase angle between them. The peak-to-peak value 400 Hz and 800 Hz (or any multiple 2nd, 3rd, etc. of 400) will change depending on their phase differences.

Wendell R. Breland

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Ok.

RS Antenna (15-2160) in Attic (entry from my closet in bedroom). Connected to a Pre-amp CM 5041DBS (on lowes website). Using the internal cable running from inside home to back of house at the satellite hub. From the hub, I just used a connected to send a cable into my basement (drilled a hole right through) since TV is right behind hub. Cable goes into the power supply of the amp and then into the TV.

Now what I initially tried to do is put the Radio Shack splitter right near the hub so one cable goes into the basement and the other cable connected to the cable (via connected) that goes back into the bedroom. Seems that was too much distance for signal to come through and therefore did not even catch one channel in my bedroom Sharp TV. Even tried connecting various RS Antennas and also the CM antenna. Nothing.

Then, just for testing purposes I tried the dirty approach of running a cable right from attic through the room to the bedroom TV. Still nothing! I really thought that would work due to the shorter cable (50 feet). Even connected the same CM antenna from basement to Sharp TV but nothing...at that point determined that Sharp TVs tuner is surely weak since basement TV picked up 10-12 digital channels while Sharp TV picked about 2.

Right now I abondened the above approach have connected the Sharp TV to an indoor amp and am getting 2 channels (that too in the evening). And am waiting for input from you and others as to what I should be doing.

I am not using the satellite multiswitch for anything. I shall await your response. Thanks for the time taken to troubleshoot this for me.

mallu2u

Antennas, rotators, boosters/preamps... for wide-band VHF/UHF

Quote:
Originally Posted by mallu2u
I would LOVE to get the attic antenna signal split working for the two TVs but for some reason it is not working. Posted the same issue in this thread: http://www.avsforum.com/avs-vb/showthread.php?t=584715.

For some reason the signal is not strong enough it seems...which surprises me since the cable run is smaller to the bedroom tv and even tried same amp from basement and also another amp from RS. Maybe you can suggest me something..that I might be missing. I would love to get that working.

Below is the text from that thread:

--------------------------------------------------------
Here is my situation:

Just bought a Sharp 37'' LCD TV for my bedroom with built-in HD tuner. My OTA feed from attic is currently going to basement.

- Tried sending the signal to bedroom by splitting at satellite hub in basement but signal does not seem to be strong enough.

- Tried splitting the OTA signal right from the antenna into the bedroom with shorter cable (since attic entrance is from bedroom closet) and still the signals seems to be weak.

- Even connected the same channel master amp from basement into bedroom and got only 1 or 2 channels while basement TV got 10 from same amp. Seems like my basement Sony XBR TV has better tuner and sharp does not.

----------------
Can you describe in sequence, including model numbers, each component, including RF Splitters, etc the TV signal goes through?

Why is the Channel Master Amp in the basement? Because that's where twin-lead goes?
It should be as close to the antenna as possible in order to overcome the downlead cable loss.

When you added an RF Splitter, where in the chain did you insert it?
Of course, it will contribute 4 dB of loss.

If you are using a Satellite Multiswitch to merge the TV signal onto all of the outputs,
there could be another serious loss of signal, unless the C-M Amp preceeds it.

holl_ands

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