[NLRS] VHF low pass filters?

[Douglas H Reed]

Congratulations! Your question has raised the most activity I've seen
here in a long while....

I agree with the others that it is most likely fundamental overload of
a preamp or amplified splitter in the neighbor's house. It is unlikely
to be harmonics of your signal. If he says the problem is only one or
two channels, check for a harmonic match. It it occurs on all
channels, it is simple RF overload.

A quarter-wave stub is the easiest option to test with, but it repeats
the notch on the odd harmonics so it could suck out a real TV channel.
A high-pass filter would be a better choice. Ideal would be to find a
inline filter with F-connectors that passes everything above 85MHz.
That will allow the FM band and all current TV channels.

I'd suggest try this first:
<http://www.ebay.com/itm/Digital-Cable-TV-Box-Filter-CATV-HDTV-/261150112671?_trksid=p3284.m263&_trkparms=algo%3DSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D21%26pmod%3D130369229197%26ps%3D54>

The above is supposed to be a high pass filter that provides >40dB
rejection of signals below 54MHz. It is made by Pico Maco as model
HPFO 54MHZ. For $7 delivered, you can't afford not to try it. I
ordered one just to measure it and see how well it works.....

I did go looking for a copy of the specs for the item. It is funny to
see it has about 8 pages of installation instructions, and somebody
asking how to install it. But the answer becomes more clear when you
see the web page that talks about using it to block pay-per-view
reporting on a cable system, and how to reset the PPV log inside the
cable converter....

After checking the Pico Macom catalog page, I don't think its going to
work. The catalog shows the filter corner starts at 54MHz and is 40dB
down by 40MHz.So that probably will not help much.... But it is
ordered and I'll be able to measure a sample next week....

In the mean time, you can use any RF filter design program to give you
values for a simple high-pass filter starting at 85MHz with any amount
of attenuation you want at 54MHz.

Good luck!

73, Doug Reed, N0NAS.