Don't know where you can buy a passband filter. Maybe be able to find some
cavity type filters for 50 MHz, but probably only surplus. Building from
scratch
is easy but takes a network analyzer to tune.

A coax stub can be either open or shorted, your preference. Cheapest way is
to
start with an open stub slightly too long and trim it to length. If you can
borrow
a signal generator and power meter, then you can tune it that way.

It's practical to get about 25 dB of loss with a stub, better is difficult
due to losses
in the conectors, cables, etc.

Rough length of the open stub would be 1/4 wavelength at 55.25 MHz, about
1.35 meters. Accounting for coax velocity factor of 0.66, the stub would be
about
0.89 meters long. Start a maybe 5-10 CM longer than that and trim to
length.

-- Tom




"GeorgeF" wrote in message
ink.net...

1) Where can one buy a passband filter for 50-52MHz?

2) When talking about coax trimmed to length, are you talking about a coax
stub? Such as cut to 1/4 wavelength of the offending freq? If so would
be ends be shorted or let open? never worked with stubs yet....

TNX
George