[K3PZN-List] 145.41 Maint

[Andy Leeds]

Steve and I made a trip up to the repeater site this afternoon and 
worked on isolating the de-sense that's been acting up lately (for those 
that remember the history we've had some little de-sense as long as we 
have had this repeater).

This morning I found that with the transmitter off I could hold the 
squelch open at -117dBm. With the transmitter on I had to provide -82dBm 
of input signal to hold open the squelch.

We tightened up some cables, adapters, jumpers, etc and things seemed to 
clear up a lot  we were back to our 1dB of normal de-sense.

We poked around a bit and checked insertion loss on the duplexer which 
was OK, and the receiver to transmitter isolation estimated at 100dB but 
I couldn't get an accurate measurement since it was down in the noise 
floor of the test equipment (good answer).

We tried adding a pass/reject can I had into the system to see if we 
could clean out that last little de-sense but placing that can on the 
exciter caused the repeater to spur badly, and putting it on the PA 
didn't help the problem (unless we de-tuned it enough to cut the overall 
output down to 3W or so). That came out of the mix and we put it all 
back together. During this experiment we did notice that the power 
control circuit was coming loose so it got new connectors soldered on.

Current power out of the duplexer is 64 W, with no measured reflected 
power, so the antenna is still good as far as SWR is concerned.

Since we were up there we also attacked the link COS logic from 2m to 
70cm and made a mod so the link logic now pulls both COS and CTSSS lines 
low on UHF so the UHF repeater will always pass link signals regardless 
of the PL mode. We looked at the other direction but after a brief 
experiment we left it alone (so if the link is on any signal on 70cm 
will get sent to 2m even if it does not have a tone on it) since I think 
a few diodes are required to hook all of those things together correctly.

I've left the link up for now just to make sure there are no odd 
behaviors over the next few hours and will let the controller turn it 
off on its own when the next macro runs.

Andy