Gary,
You're welcome!
While it is possible to convert a bandpass cavity into a notch cavity by
changing the coupling loop(s), it is always better to engineer the
system with the proper components. So, put the TWPC-1005-1 cavity on
the shelf for now, because it's not going to do anything for this
problem.
That said, in this particular case, it might be instructive (and
possibly productive) to try the DCI filter in the receive side, between
the duplexer RX connector and the receiver input. I have just scoped a
DCI 146-4H on my network analyzer and found that it has a flat passband
between 144-148 MHz with about 0.6 dB insertion loss, and about -109 dB
response between 88 and 108 MHz. If you have double-shielded cable and
good connectors between the DCI filter and the receiver, it might just
work. It's certainly worth the effort to try. I'd be a lot happier if
it had N connectors instead of SO-239s!
73, Eric Lemmon WB6FLY
--- Gary K2UQ wrote---
Eric,
Thank you for the explanation of the TWPC-4508-2 bandpass filter and its
application. This is the way people like me who have been playing with
this stuff gets straight info on how things really work without spending
wasted hours at the repeater site.
I thought this filter could be hooked either as a pass or notch cavity.
The FM broadcast station is very close to my 2 meter repeater antenna.
I thought proper approach would be put FM TWPC-1005-1 cavity in the Rx
side of my duplexer to notch out FM station. Or, should I put a DCI
filter in line someplace. Or add a pass cavity on Rx side. What happens
to the RF rejection on a filter such as a DCI for 2 meters when the freq
you want to reject is say 46.205 MHz away from 2 meter repeater input.
How much attenuation does a filter such as a DCI provide at these far
away freqs? I don't want to be boring for those who are in the know.
But I am aware there is a lot of good knowledge here. Not everyone tuned
into this reflector is an expert. That's why many are here.... to help
us guys learn.
Thanks,
Gary K2UQ
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