[mythtv-users] IVTV 0.8.1 and PVR 500 with new Samsung, tuners

Brian Wood beww at beww.org
Thu Dec 7 18:33:24 UTC 2006

On Dec 7, 2006, at 10:59 AM, John Drescher wrote:

>> Sounds like something (perhaps the internal amplifier in the 500
>> card) is getting overloaded, as what you describe sounds like
>> "composite triple beat", often known as "cross-mod".
>> You probably want to use an actual attenuator instead of splitters.
>> While the splitters will drop the level, the attenuator will do so in
>> a "flatter" manner across the spectrum.
> I understand. I actually am an EE but I did not study RF at all. I am
> going to do more testing when I get a free minute.... One thing I am
> going to do is to remove my cable amp from the basment and replace it
> with a splitter. This should reduce the signal a bit as the cable amp
> is +7db per port and the splitter I will replace it with will be -7db
> per port.

EE and "didn't study RF" ? Oh well, "The times they are a changin'" I  
guess, you probably didn't study vacuum-tube design either :-)

Obviously if you can eliminate an amplifier it can't hurt, amplifying  
a signal only to throw it away in attenuators is a bit crazy.

You have to look at your amplifier not in isolation but as the end of  
a long chain of cascaded amps in the cable system. An amplifier  
capable of handling the multiple channels on a modern cable system is  
expensive, certainly an "antenna" type single-ended unit won't do it  
without many distortion products, and "cross-hatching" is only one of  
the may ways that can manifest itself.

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