[RFI] Mast-mount TV Pre-Amp -- Avoiding RFI & Overload?

[Roger (K8RI)]

kd4e wrote:
> Actually, a digital signal is either real good or it is real 
> gone.
>   
There is a thin band, or very narrow range where the signal breaks up, 
pixelizes, pauses, or goes out of sync
between the audio and video, but it is so narrow it is seldom seen. When 
the signal reaches that level it is susceptible to all sorts of 
interference.

> Here in the fringe area we need help to get the signal strength
> we need for a consistent signal lock.
>
>   
I've found the digital signals to be far more reliable than the analog. 
I now get stations from Lansing and the Northern Detroit area that look 
as good as locals where the same stations on analog aren't worth 
watching. I now receive about twice as many off the air signals as I did 
with analog and the antennas don't seem to be quite as fussy to 
pointing.  Unfortunately there are two groups of stations with one from 
SE to SW with another on about 330 degrees.  So I have two antennas 
which I switch between.  BTW these are only about 10' from the tribander 
which gets the legal limit.
> If I could find a mast-mount pre-amp which includes
> bandpass and low-pass filters, to keep non-TV signals
> out, then it should do a good job.
>   
I use antenna mounted preamps on two large UHF antennas that pick up 
both VHF and UHF.  The low band VHF is strong enough that the UHF 
antenna does right well. Of course the distance is only about 35 to 40 
miles over flat land and my antennas are at 90 plus feet.  HOWEVER they 
are only about 15 to 20 feet above the 144/440 diamond repeater antenna 
(Up to 160W but normally 50), about 20' below the 7L C3i 6-meter antenna 
being fed a KW and about 30' below the 144 and 440 arrays with the 
capability of 1KW out on the 144 band. We are limited to 50 watts on 
440.  So far no problems with my antennas but I did get into channel 12 
on my neighbor's TV in the garage using rabbit ears.  I gave him a good, 
but small all band TV antenna and that ended that problem.

I'd go with a 1/4 wave stub to notch out the 2-meter band if it's a 
problem or build a filter using a group of stubs as they recommend 
behind the henry 2002A.    A KW on six doesn't seem to bother anything here.

73

Roger (K8RI)
>
>  > WA3GIN wrote:
>   
>> THEY ARE ALL JUNK
>> WITH DIGITAL YOU MAY NOT NEED A PREAMP
>>     
>
>
>