In-Line amplifier

[jenom]

Just bought a new Digiwave A04-20 20 dB 950-2150 Mhz In-line amplifier on E-bay, hoping to improve a signal sthrenght from Hispasat 30W, after 100 ft cable+splitter+22Khz switch+ Diseqc switch.

Connected between the LNB input on my receiver and the incoming cable, checked levels on channels, but I do not see any increase in the signal levels or in fact any change !

Maybe it is dead ? Is there any other way to find out if it is working ?
Thanks

 

[updatelee]

really the only way to see if its working is with a spectrum analyzer. but on the same note, 100ft isnt long at all and the amp will not help you out, it'll either do nothing, or if its really cheap like many are, make things worse.

amp's amplify the good and the bad, and often add their own distortion into the mix. think of it like this.

you have an am radio, not very clear right, now walk 400ft away, not only is it not clear, but super quiet. crank the volume to amplify it, now it sounds a little worse, but at least you can hear it.

now take a sirrius radio, sounds great, crystal clear, walk 400ft, its too quiet, amplify it and it doesnt sound quite as good, but still more then acceptable, but you can hear it great.

amp's dont help your signal quality at all. if anything they lower it.

 

[jenom]

I do not see neither a positive or negative effect so far, thinking, to put it just next after the LNB and see what will happen ?

 

[Larry1]

The signal amplifier is working as you are getting a signal. If it was not working, you would not get a signal. The problem is, the amplifier increases the signal, and the Automatic Gain Control circuits in the receiver adjust the tuners amplification to have a signal of a certain voltage. Since the inline amplifier increased the signal, the tuners AGC circuitry adjusts it amplification to compensate for the larger voltage at the tuner. i.e it does not have to amplify the incoming signal nearly as much. So the data coming out of the tuner is the same, you have just placed the amplification point outside of the tuner.
Now what you really wanted to happen is for the signal to have less noise, not more amplitude, for your Quality level would rise.

 

[Stefan]

Amplifiers ALWAYS add noise to the signal. That is noise that wasn't in the signal to begin with. The higher quality amplifiers may add less but there's no such thing as a perfect amplifier and they all add some. In fact if you usually look at the noise figure rating of these amplifiers you'll generally see it's much worse than most LNBs and of course the noise added by the amplifier will always be in addition to the noise the LNB introduces to begin with. Also generally the higher the gain the amplifier provides usually the more noise it will add. Also as has already been said by others here, in addition to adding new noise to the signal they also amplify the noise that's already present. So, with all this in mind, why would anyone use an amplifier? The answer is you don't unless you have to and this would only be in situations where you have very long cable runs that result in a lot of signal loss between the LNB and receiver and/or situations where you have the signal split many ways with a passive splitter. Otherwise your generally almost always better off staying away from amplifiers.

 

[vfrjim]

Take it from me, forget about an amp at 100', unless you are splitting it to 6 receivers. It caused me all hell with my SG2100 motor. Go and check all your connections and tweak your dish, more bang with no bucks.

 

[jenom]

When I connected amplifier directly after the LNB, immediately noticed that some radio channels have gone missing.
So I placed it back at the input of the receiver, and now I gave attention not just to the signal strenght, but also the "signal quality" levels.
While the "signal strenght" remained the same with or without the amplifier, the "signal quality" level went up when the amplifier was connected, from 60 to 77, from 72 to 79, from 54 to 67.
I read somewhere else, if the amplifier is "increasing" the "signal quality" level, it is a good thing for the receiver to decode the signal with less effort (faster/easier).

Here is the original article:

The easy way to check is to look at the Signal Strength and Quality bars on the box, with and without the amplifier. If strength goes up but quality goes down or stays unchanged, the amplifier isn't helping. If quality goes up, then the amplifier is useful.

Signal quality isn't related to strength at all. With a digital signal, any interference shows up as corruption of the digital data. To protect against that, the signal has some built-in redundancy, i.e. some duplicate information. When the decoder detects that the inforrmation has been corrupted it can use the redundant info to reconstruct the correct value. The signal quality is a measure of how hard the decoder is having to work to do that correction. Eventually the corruption can get so bad (quality so low) that the decoder cannot reconstruct the data, and the picture will break up. It doesn't matter how weak or strong the signal is, just how 'undamaged'.

 

[updatelee]

honestly if the amp is helping on a 100ft run, youve got other serious issues. a shorted coax, connector, switch, or lnb, something isnt right.