Amplification: Before or after the split

techno935

techno935

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Does it make any difference in quality? Just curious. The hi-def receiver has a 10 db amp in the living room, but none of the other TVs are amped up.

Now, if I amp up the line before the split, will I see more gain if I amp before I split? I've always wondered about that as opposed to running individual amps on each receiver.
 
T

Tower Guy

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Nov 1, 2005
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Does it make any difference in quality? Just curious. The hi-def receiver has a 10 db amp in the living room, but none of the other TVs are amped up.

Now, if I amp up the line before the split, will I see more gain if I amp before I split? I've always wondered about that as opposed to running individual amps on each receiver.

If the amplifier is not overloaded by strong signals, the system performance will increase.
 
G

gpat

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Oct 27, 2007
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I always heard it was better to push than pull.
 
primestar31

primestar31

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Does it make any difference in quality? Just curious. The hi-def receiver has a 10 db amp in the living room, but none of the other TVs are amped up.

Now, if I amp up the line before the split, will I see more gain if I amp before I split? I've always wondered about that as opposed to running individual amps on each receiver.

I used to install OTA tv towers and antennas with Winegard equipment. It's always best to have the amplifier as close to the ANTENNA as possible. You want the lowest noise amplifier you can find (more important than anything else), and at least 18DB gain in most cases for splits. You want the best signal, and least noise input right at the amp input, that's why it should be close to the antenna. By close, I mean within 18-30 inches. After 100+ feet of cable, the signal would already be degraded and noisier, so it's not a good idea to have the amp right by the receiver.

So, YES, it's better to "PUSH" than pull, and that's why!
 
R

raj2001

Well-Known SatelliteGuys Member
Sep 20, 2003
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Wantage, NJ
You should have your amp as close to the signal source as possible, and before any devices that cause attenuation, like splitters.

The reason is that when a signal is attenuated, for example at a splitter, the signal to noise ratio usually decreases. This means that when you amplify after the splitter you are amplifying noise as well as signal.

You will get a better signal to noise ratio placing your amplifier before the splitter.

Ultimately for most consumer distribution systems it won't matter, because signal is sufficiently strong enough so that the difference in S/N before and after the splitter is usually not really that great.
 
techno935

techno935

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I'm a consumer, but I'm rollin out hardcore commercialized SMATV at the house. Integrating FTA with RF modulators pretty soon here. :) Thanks for the answers!
 
S

Smith P.

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"The reason is that when a signal is attenuated, for example at a splitter, the signal to noise ratio usually decreases."
Not necessary; most important other two major factors: EMI and non-linear components. Attenuation itself doesn't increase SNR.
 
pabeader

pabeader

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if the signal drops by 3db (a splitter) but the noise doesn't then the signal to noise ratio will ????
 
primestar31

primestar31

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if the signal drops by 3db (a splitter) but the noise doesn't then the signal to noise ratio will ????

Stay the same. Realize that every 3db of gain is a DOUBLING of power. 3db loss, is HALVING of the signal. The signal to NOISE ratio % will stay the same, percentage-wise. Lower noise, is always more important than greater signal, period!

Try to find an amp that's no greater than 1-2db noise MAX. It really is worth paying the extra money for this.
 
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S

Smith P.

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Technically is not that absolutely correct.
Splitter have internal components what will add some noise level ie decrease SNR. But it is not attenuation itself.
 
Bear Paws

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if the signal drops by 3db (a splitter) but the noise doesn't then the signal to noise ratio will ????
????

Back to school ! You got C- :).
What is a noise ??? Something what never decreasing ? Really ?
Your generous. I flunked him.:D

In a embarrassing attempt to keep it painfully simple;
Noise is signal but of the unwanted kind. In some circumstances the "signal" is the noise, like as in back round noise or interference from other stations on the same freq or harmonic, or multi path... If you amplify or attenuate a "signal" you do it to both unless you have filters in the system say similar to a FM trap. . But those too cause signal loss and noise. Yes, Smithy is right you can introduce more noise with components. The idea is to have more signal to over come the built in noise of your sets front end [ AKA Signal to noise ratio, and with out adding more noise to the sets front end with the other dudads you hang on the system like amps, splitters etc..
The Amplifier is the major culprit of noise [of the unwanted kind].. If the noise introduced by the amplifier is greater than the TV'S or STB threshold forget about getting a lock on the leader signal.

Unlike with analog , Noise in DTV is not as a major issue so long its below "lock" levels. THe sig level meter on screen is usually relative signal strength over lock threshold. Not over all S-voltage or field strength. Most people miss use that "meter".. You could be down the street from the transmitter and get a reading of 25 % not "locked" because of extraneous noise from other sources being greater than the signal even though the voltage in the ant is [kidding] 1000 volts.

This is somewhat related and very interesting for mountain or city dwellers.DISTRIBUTION of digital television signals

There is more to the article than this . But this paragraph is something many of us should know. It has to do with SNR also.

As expected, the largest antenna, the 3028 eight-bay UHF screen, had the greatest gain on the lowest DTV channel (26). Higher in frequency, Channel Master's 3023 deep suburban yagi was the best performer in terms of gain, outdistancing the eight-bay by at least 3 dB. At the upper end of the UHF TV spectrum, however, the four-bay 3021 was just a hair better on channels 64 and 67. Frequency response is definitely something that you will want to keep in mind as you select a terrestrial DTV antenna.
Although it is true that gain and directionality go hand in hand, not all high-gain antennas reject multipath equally. A long yagi, like Channel Master's 3023, is quite adept at handling signal reflections in a low-multipath setting with a fairly unobstructed reception path, but it can be overwhelmed by secondary and even tertiary signal reflections when used in an urban environment.
 
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