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Question Correct way split OTA signal using amplifier ( AVS Forum HDTV Technical )
Updated: 2008-06-08 07:46:25 (22)
Correct way split OTA signal using amplifier

I have a splitter which splits my OTA signal into three, with one out at -3.5 and the other two at -7. I have my main TV hooked up to the -3.5 which is AFAIK the correct way. However, I don't know where I have to put an amplifier so I get 100% signal. My local channels are at 96% (FOX), high 80% (CBS and NBC) and 75% for ABC. I thought it would be same signal strength on all, so that was surprising to sell. I have an amplifier (not needed to plug into an outlet), but my strength didn't increase AT ALL (I tried it before AND after the split, but no increase anywhere). Also when I hooked up my main split to -7 output, it was still the same strength. What am I doing wrong? Or can I do anything to gain signal strength? Is there a certain amplifier I should look for that would be better than others?

Answers: Correct way split OTA signal using amplifier ( AVS Forum HDTV Technical )
Correct way split OTA signal using amplifier

Well,
If you were to add a preamp, it would be before the splitter. Or better still, get a distribution amplifier that has (typically 4) multiple outlets as the splitter is built-in and matched to the preamp. They're real cheap.

However, with the numbers your getting I wouldn't mess with it. There is a downside to raising your noise floor and giving multipath a leg up to with the increase in amplification...

And yes, the one marked 3.5 has only a loss of 3.5 Decibels as opposed to the other two that loose a ful 7-Db.

Picture a two way splitter,

now picture a second two way splitter on
one of the outlets of the first one...

See why one has 3.5, and the other two a loss of 7?

Now on the the preamp you have. My instinct says your holding a mast mount preamp that only has two RF connectors. What your not seeing is that the one marked ''To TV'' actually is a power jack as well.

At the TV end of the downlead a power injector would put a DC voltage on the lead to travel up to and power the preamp inside. The amplified TV signal piggy-backs the DC current back down to the power injector.

The power injector removes the supply voltage with a DC blocking capacitor and passes it on the the TV.

Can you give me the number/names on the preamp unit?
Perhaps I can give you a number to Google/eBay for...

WeThePeople

Correct way split OTA signal using amplifier

Quote:
Originally Posted by LukFilm
I have an amplifier (not needed to plug into an outlet), but my strength didn't increase AT ALL (I tried it before AND after the split, but no increase anywhere).
No such thing as an amplifier that doesn't need to be plugged in. Amplifiers are active devices -- they need to get power to operate from somewhere.

If it is this one: http://www.affordablehdtv.com/terk-b...4.html?ref=100, it gets its power from the satellite receiver. If it's something like this one: http://www.radioshack.com/product/in...entPage=search, the amp gets its power from the power injector, which can be located at the outlet (or before a splitter) while the amp is at the antenna.

egnlsn

Correct way split OTA signal using amplifier

Quote:
See why one has 3.5, and the other two a loss of 7?
use a 3 way splitter. The loss is 5.5 db.

there are 2 versions of a 3 way so be careful when purchasing


5.5
5.5
5.5

3.5
7.0
7.0

A distribution amp or powered splitter is not necessary if you are using a preamp....unless there is an extremely long leg to amplify well is excess of 100 ft. Just use splitters and balance the losses on long and short runs. Do the math on paper to calculate and plan.

2 way -3.5
3 way -5.5
4 way -7.5

-1 db per 16' of rg6

Rick0725

Correct way split OTA signal using amplifier

You forgot to mention the 5.5's are well balanced out to 1,000-Mhz (1-Ghz) for newer cable srvices, those older ones ring on the two 7's badly on the top channels.
Good for OTA (~899-Mhz) only.

And I agree he should already have enough gain to use a bare splitter instead of a distribution amp,
but if you read his opener you'll see he isn't.

He's trying to real hard though.

We won't know what he's using until he posts some product data...

WeThePeople

Correct way split OTA signal using amplifier

If you're getting good reception with no dropouts, don't worry about the numbers. The signal strength meter is typically an indication of signal-to-noise ratio, and you can't get better SNR than is actually available at your antenna in any case.

nybbler

Correct way split OTA signal using amplifier

I'm getting dropouts on ABC when it's not perfect weather (my local towers are about 5 miles aways and I have an external antenna).

OK, what I was using as signal booster is 10 dB in-line amplifier from GE. So I was using it wrong and when I dug around, I found what appears to be a complementary device which says Power Injector for use with 10 dB in-line amplifier, model AV93241 on the part that plug into the outlet. As I'm very new at this (duh!) please tell me where exactly I should plug this in for best results. I also found another item which says Channel Master Model 3037 Antenna Amplifier on the power brick and on the thing with two connectors it says Power Injector and one side "To TV" and other "To Amp". I remember this was from my old VOOM set up to get locals through my Voom box, but don't remember how it was hooked up. This one, unlike the GE, has two connectors the same, so I have to have two cables connecting through this power injector, I guess.

Thank you for your help, I'm trying to get this done ASAP as I will have the splitter in the ceiling and I think my contractors are starting the work on it very shortly.

LukFilm

Correct way split OTA signal using amplifier

Quote:
Originally Posted by egnlsn
No such thing as an amplifier that doesn't need to be plugged in. Amplifiers are active devices -- they need to get power to operate from somewhere.

If it's something like this one: http://www.radioshack.com/product/in...entPage=search, the amp gets its power from the power injector, which can be located at the outlet (or before a splitter) while the amp is at the antenna.

Yes, this is what I have and was trying to describe above. I also have the Channel Master, please let me know which is appears to be better.

LukFilm

Correct way split OTA signal using amplifier

OK, I downloaded the user guide from RadioShack's website and now know how to hook this up. However, one review stated that "Note: This device will not amplify a weak signal or improve a poor reception." Does that mean that I shouldn't bother with this? My main cable run from the antenna to the splitter is about 20 feet and then from there to the TVs about 30 more feet. I had a roof redone, so I have the cable go directly under it hence the short run.

I also don't understand this: "I agree he should already have enough gain to use a bare splitter instead of a distribution amp."

What's gain? What's a distribution amp? Do I need these?

LukFilm

Correct way split OTA signal using amplifier

Most important rule is no splitters between the power injector and the preamp.

The GE 10-Db gain bullet is OK if your overcoming splitters that are near it.
They really stunk on long line feeds though.

The channel master has me more intrigued. Do you have a number on the preamp part?
The 3037 is the number for the the power injector only...

I am hoping the preamp is an outdoor rated mast mount preamp
that goes right at the antenna where a preamp belongs.

WeThePeople

Correct way split OTA signal using amplifier

Quote:
Originally Posted by LukFilm
I'm getting dropouts on ABC when it's not perfect weather (my local towers are about 5 miles aways and I have an external antenna).
If you are that close, you should not need any kind of amplification at all. I'm about 12 miles away and have 4 outlets with no amplification. There is such a thing as too much signal.

I have to wonder how your connections are -- especially the one(s) outside, since it goes downhill during inclement weather.

Also, make sure the splitter is 5-900MHz or above. If it is only a 600MHz splitter, that could even be most of your problem.

egnlsn

Correct way split OTA signal using amplifier

Quote:
Originally Posted by egnlsn
If you are that close, you should not need any kind of amplification at all. I'm about 12 miles away and have 4 outlets with no amplification. There is such a thing as too much signal.

I have to wonder how your connections are -- especially the one(s) outside, since it goes downhill during inclement weather.

Also, make sure the splitter is 5-900MHz or above. If it is only a 600MHz splitter, that could even be most of your problem.
It's just one main cable from the antenna going into the house. I do have a decent splitter (5-1000MHz), so that's not a problem. Perhaps the connection right at the antenna isn't good, I'll have to check that out now that you mention it. I did change antennas when I thought that an issue I had was with the antenna (turns out it was a cable that was cut, duh!) so maybe that's when I messed it up.

LukFilm

Correct way split OTA signal using amplifier

Quote:
Originally Posted by WeThePeople
Most important rule is no splitters between the power injector and the preamp.

The GE 10-Db gain bullet is OK if your overcoming splitters that are near it.
They really stunk on long line feeds though.

The channel master has me more intrigued. Do you have a number on the preamp part?
The 3037 is the number for the the power injector only...

I am hoping the preamp is an outdoor rated mast mount preamp
that goes right at the antenna where a preamp belongs.
Bummer, apparently I already threw it away with the antenna couple of months ago (after having it in my garage for over a year). Too bad I didn't know there was an amp in there! So I guess I can throw away the power injector too, right?

LukFilm

Correct way split OTA signal using amplifier

well there's not much use for it. That perticulat model will output around 15 volts dc negative ground at a little under a half amp on the ''to ant'' jack...

WeThePeople

Correct way split OTA signal using amplifier

Quote:
Originally Posted by LukFilm
It's just one main cable from the antenna going into the house. I do have a decent splitter (5-1000MHz), so that's not a problem. Perhaps the connection right at the antenna isn't good, I'll have to check that out now that you mention it. I did change antennas when I thought that an issue I had was with the antenna (turns out it was a cable that was cut, duh!) so maybe that's when I messed it up.
Closely inspect the connector itself and make sure that there are no strands of braid inside that are close to the center conductor. Same with all connections, but particularly outside, as the issue seems to be weather-related.

At 5 miles from the transmitters, you should be fine with just a pair of rabbit ears. You should not need any kind of amplifier-- internal or external, and you mentioned that you have one on an outdoor antenna.

egnlsn

Correct way split OTA signal using amplifier

Attention newbies. The signal strength % is just some kind of calculated value that seems to vary inversely with the amount of error correction capability being used. Within a certain range, you can vary actual signal strength, measured in dBm or dBmV, by more than a thousand-fold without causing the signal strength % to change.

AntAltMike

Correct way split OTA signal using amplifier

Quote:
Originally Posted by WeThePeople
Most important rule is no splitters between the power injector and the preamp.
Not true. Many two-way splitters pass power on one port, which is most commonly denoted by a line drawn on the label from the common port to the power passing port

Quote:
The GE 10-Db gain bullet is OK if your overcoming splitters that are near it.
They really stunk on long line feeds though.
An inexpensive, 10dB bullet amp amplifies a signal by 10dB and is generally noisier than a better quality pre-amp, with most 10dB bullet amps I've looked at having noise figures of 4dB or more.

These amps are not designed to handle high signal power, and if you use one in a system sourced by transmitters 5 miles away, the signals will excessively "intermodulate" and degrade one another.

With digital signals, unlike analog signals, you are sometimes better off "preamplifying" them, if necessary, at the end of the coax away from the antenna rather than near the antenna, but there is nothing in LukFilm's situation he has described to indicate that he needs or would in any way benefit from one.

Quote:
The channel master has me more intrigued. Do you have a number on the preamp part? The 3037 is the number for the the power injector only...
The 777X Channel Master preamps have gains of 23dB and 26dB, which is the last thing that LukFilm needs.

LukFilm either has a connection problem or a multipath signal problem.

AntAltMike

Correct way split OTA signal using amplifier

Quote:
Originally Posted by WeThePeople
You forgot to mention the 5.5's are well balanced out to 1,000-Mhz (1-Ghz) for newer cable services, those older ones ring on the two 7's badly on the top channels.
Good for OTA (~899-Mhz) only.
Off-air presently goes up to channel 69 (806 MHz) and that will be cut back to channel 51 (698 MHz) shortly. I have never come across a cable company that goes above cable channel 135 (864 MHz). I don't think I've seen a three-way or four-way splitter that had any troubles at the top of the broadcast frequency band made within the last twenty years.

LukFilm may do better posting in his local forum. Someone there may know of local terrain or signal refection problems, as well as how he might optimize his installation to simultaneously receiver any weak distant signals that might also be present.

AntAltMike

Correct way split OTA signal using amplifier

I agree with Mike about the following:
False misleading intuitiveness of new Signal Strength readouts
10 Bullet's are cheap and have higher noise factor,
And a 5 milre away transmitter may overload the puppy.
He never said he through out a 7777 (I'd hafta cry...).
He has a connection, coax water intrusion, overload problem.
He should find his 'local here and see if others share his misery:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=45

I'm pondering:
Existing multipath in signal, when amplified, gets worse sent through cable lengths
(Sounds perfectably plausable, newer digital signals warrant testing this theory)


I disagree:
Go to you local RS, WalMart, CC, BB, Etc. You WON'T find a DC=Pass splitter anywhere!
They have to be ordered (I am welcome to anyone that has seen them in-the-wild).

Lastly, I've had more than my share of splitters in my hand that read ~800-Mhz,
They just stunk at high-UHF, and do snow-up the top cable channels...

WeThePeople

Correct way split OTA signal using amplifier

LOL, so I disconnected and reconnected the cable from the antenna and now I get 98% on all channels. Sorry for the useless thread And thanks for all your help, I learned some new things today.

LukFilm

Correct way split OTA signal using amplifier

Quote:
Originally Posted by LukFilm
Sorry for the useless thread And thanks for all your help, I learned some new things today.
Not a useless thread -- sharing of information/ideas is not useless.

egnlsn

Correct way split OTA signal using amplifier

Actually slight correction. I get 98% on NBC, CBS and FOX, but ABC is still at 75%. Anything I can do?

LukFilm

Correct way split OTA signal using amplifier

I just picked up a 4 way Bi-Directional RF Amplifier, 54-1000MHz, DC 12 v input (adapter included), RCA model DT140M at BB. I have two Antennas. One is facing South out the back window of the 2nd floor. One is facing North out the front window of the 2nd floor. I've got about 50ft. of coax running to my digital tuner in my computer. I also picked up some more coax (two 12ft. and two more 25ft.), and a Diplexer hoping I can join the two antennas then split the signal to my TV and VCR. Do I have to have the same length of coax from the antennas to the Diplexer? Where should I put the splitter? Is what I want to do even possible? I'm getting strong signals. I just have one favorite channel in the opposite direction and would rather not go through a rooftop installation. Thanks in advance for any suggestions.

KLCJ

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