[mythtv-users] Strong signal, ugly artifacts...

Brian Wood beww at beww.org
Sun Jun 14 21:25:36 UTC 2009

On Sunday 14 June 2009 14:33:16 Andrea Giuliano wrote:
> Well, I checked cables and dish, nothing changed.
> One thing I should have mentioned before is that I have an in-line
> amplifier that should give a gain of 20 dB, but MythTV always reports
> 4.8 dB despite the amplifier is present or not. In the latter case,
> MythTV reports a signal strength less than 10%.
> If MythTV is not fooling me, the amplifier is gone: 4.8 dB is less than
> the gain it should give!
> On the other hand, the signal strength is dramatically affected by the
> amplifier.

You may be overloading the amplifier, either by too strong a signal input or 
by having too many channels.

Make sure the amp is designed for the channel loading you have, and that it's 
push-pull if you are using the mid-band (a single-ended amplifier will throw 
second harmonics from the low band into the mid-band, a PP amp will not do 
this (as much)).

Amplifiers are happiest with all the input channels close to each other in 
level. If you have a strong local station (or even strong local FM stations) 
you will overload the amp. You may need to attenuate the local station(s) to 
prevent this.

So double-check the amplifier specifications and make sure you are operating 
within them.

beww at beww.org

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