Lines between cavities and the antenna "T"
For some reason this chapter is missing. This is my input. Alan VK2ZIW 2m and 6m cavities
Lines between cavities
Obviously good coax cables. Loss is not a problem for the short lengths used here, but leakage is important. Use coax, either double shielded or with good braid.
Cable lengths. Are they always y/4 ?
Measurement: Put 50 ohm terminator on a "T" piece and the adjustable line to your cavity. Measure the SWR into this combination. Adjust the line length for best SWR. If your adjustable line is longer than y/2, (mine is) subtract y/2 from your length. Remember the velocity factor of your adjustable line will not be the same as your coax. Now make a lead and test it. Accuracy within 1cm for 2m will do. You could use a zillion coax joiners, male to male, female to female, end to end, say 10 of them for 2m. If you have a network analyser go for it.
The antenna "T"
A circulator would be nice. A rare device. Not needed here.
We want all the Rx signal to go down the Rx cavity path and not experience a bad SWR caused by the lead to the Tx cavities. As mentioned above, with BpBr cavities of the single loop and series capacitor type, we just use y/4 lines. Likewise, the Tx signal needs to not see a bad SWR at the "T" caused by the Rx chain.
BpBr cavities of the single loop and series capacitor type make life easy!!!
Bandpass cavities also have this problem, so are not used as the 1st cavity after the antenna "T".
Unless somebody has done the hard work and worked out the correct coax lengths.
============ Testing ================
If you've never seen the cavity set before and suspect it may have been fiddled with, start by putting
terminators on the Rx and Tx ports and measure the SWR into the antenna "T". You should see good SWR at both
the Rx and Tx frequencies. If not. move the terminators to, after the 1st cavities, and test again.
Cavities further down the chain may be off frequency.