Quote:
|
Any suggestions on a filter?
|
All FM filters are not equal. If I'm using a preamp with an FM filter, I have to accept its attenuation curve. If I pick a filter for a system without a preamp, or a system that needs even more attenuation than provided by the preamp FM filter, I select a filter that attenuates the frequencies of the strongest FM signals. A HLSJ makes an effective FM filter because it attenuates everything below channel 7 including the FM band. Some filter curves in the attachments.
Attachment 1: Antennas Direct FM trap vs Radio Shack 15-577. Notice that the AD does better at the low end of the FM band than at the high end. The RS attenuates better at the high end, but doesn't at the low 88 MHz end to allow reception of TV CH 6.
Attachment 2: The MCM FM trap does well across the whole FM band.
Attachment 3: A HLSJ used as an FM filter.
Attachment 4: I was concerned that a HLSJ might affect reception of UHF signals. ADTech did this test that shows the attenuation of the Holland HLSJ is of no concern for UHF signals.
If FMFOOL is correct, your two strongest signals are CJKX-FM on 95.9 MHz at -24.1 dBm and CKQT-FM on 94.9 MHz at -25.3 dBm.
Your strongest TV signal is CICA-DT at -39.6 dBm, which is 15.5 dB weaker than CJKX-FM.
FM can interfere with TV signals in two ways: fundamental overload, even affecting UHF if the FM signals are very much stronger (not likely in your case), or 2nd harmonic (2x its frequency) of FM signal falling on VHF-High channel frequency.
https://en.wikipedia.org/wiki/North_...on_frequencies