> "Doug Hutchison" <[EMAIL PROTECTED]> wrote: > 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
Hi Doug, "Normally"... the length from the transmitter/power amplifier to the first band-pass cavitiy is not considered a critical length in most vhf/uhf applications. You mention your system is a dual antenna system... so that means in most cases each b-p cavity goes to its own antenna, which means no frequency combine networks are needed and relative to the scheme of things and no cable lengths are ultra critical. However "comma" coax lengths can be a magic black box device (not that big a mistery really) used for impedance & phase changes so length can play a role in many applications. If you're at uhf/vhf just keep in mind the 1/2 wave rule of thumb where anything put into a halve/half wave section (or any multiple there of) of feedline is expected to be the same animal at the other end of the pipe. This is what you might try to keep in mind in your non critical dual antenna system. Also remember the physical length of coax is shorter than the free space (air) 1/2 wave length and the cavities have internal loop or probe lengths that should be considered in critical cable systems. In your case pretty much any quality 1/2 wave length or multiple of feed line should be just peachy. cheers, skipp
