Doug,
About the best answer is, "It depends."
In the case of the TX cable, not only does the optimum length depend upon
the frequency, but it also needs to be based upon the design of the cavity
and the transmitter. That's because there are three parts of that cable:
The length of the coupling loop or probe inside the cavity, the length of
the jumper cable itself, and the length of the cable inside the transmitter
between the PA and the output connector. Since you may not know the first
and third lengths, you can't simply make a jumper cable to an exact quarter
wavelength or multiple thereof and expect it to work.
Perhaps the best course of action is to experiment with various lengths, to
see which provide the best match. An alternative is to install an impedance
matcher ("Z-Matcher") at the transmitter output, and tune for maximum
output.
In the case of the RX cable, the length is not usually critical- but a
little experimentation can't hurt.
73, Eric Lemmon WB6FLY
-----Original Message-----
From: [email protected]
[mailto:[EMAIL PROTECTED] On Behalf Of Doug Hutchison
Sent: Thursday, December 28, 2006 4:43 AM
To: [email protected]
Subject: [Repeater-Builder] Cavity Filter advice
Hello,
Seeking some guidance re the correct length of cable to use between
cavity and transmitter, cavity and receiver on a dual antenna system.
(each line has its own BP/BR filters for the moment)
Is it 1/4 wave or are multiples of 1/4 wave acceptable?
Doug - GM7SVK
