Well, probably true. Don't transmit through it! The computer with the
shorted-stub
spreadsheet on it is broken, so I can't look at the loss vs. frequency. It's
a simple
Excel sheet that models the complex transmission-line equation (including
loss)
of the stub against the feedline. Hoped it wouldn't be that bad at 10%
separation,
but am flying blind until I can get access to it and run the numbers.

-- Tom



"Dale Parfitt" wrote in message
news:jZAjd.2538$bH2.1351@trnddc09...

"Tom" wrote in message
news:YBvjd.2272$bH2.1471@trnddc09...
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.

You may achieve -25dB loss at CH2 video, but unfortunately you will also
have high loss at 50MHz, and a VSWR that is out of sight.
Build one and see for yourself.

Dale W4OP