[NLRS] VHF low pass filters?

[Bill Davis]

   Similar issue here for years 
.. good luck. My TV system is unaffected by my operations but I designed
 the TV system to be tolerant ... tuned filters before preamp etc. We 
are VERY fringe with only one station being less than 50miles.



   The nature of the cause will be interesting. I have a neighbor here to 
my north west about 1000ft away that has always been a problem. The 
switch to DTV didn't help here at all. WHY?? Because the neighbor has a antenna 
preamp (mast mounted) and fed with about 6 or 8ft of 300ohm twin lead. 
She can detect 5watts at 6meters with that mess. The antenna is on a 
48ft tower with 8ft or so of mast out the top. The untuned preamp front 
end is overloaded easily on many 50MHZ and greater bands and it is all 
down hill from there. We operate right in the freq range the preamps are "designed" to amplify. 


   IF they have a preamp, filtering before the amp will be the only hope 
with that much 6m RF. I doubt there are any TV preamps out there that 
have any rejection for the old low VHF channels. FM traps yes .... 
rejection at 50MHz ... nope. Good feedline and preamp in the house where it can be filtered would be what I would encourage IF they NEED a preamp at all. I don't know the 
TV paths for your area.

  IF the issue is 6m only and you can get ahead of the preamp, the stub filter will most probably solve the issue.


  MS digital operations are problematic too since you will be running 
extended periods of regular on/off operations. Drives the TV viewer mad 
... the pix is perfect for 34sec then blitzed for the TX period only to 
be repeated a min later with no know end for the viewer. Working Es may 
be somewhat better for the viewer with less regular TX periods. I LISTEN lots and TX little, I also avoid working "strings". For my MS 
operations I try to do very last evenings or early mornings. 


  I used to call this neighbor a week or so before a contest indicating 
my impending operations and indicating a willingness to be a bit 
flexible if there was some "special" program that they just had to see. 
That seemed to "work" for a year or so, and then they just became too 
irrational. I took great pains in explaining the issue and solution, 
even in writing. However to them they have great $$$ tied up in their 
OLD TV system 20yrs ago and the cause of all of their TV problems are MY problem.
73   Bill K0AWU


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