Hi all I'm working on a 1 mc. split repeater using this duplexer. Transmitter is a VHF Engineering; output is 1 watt. I'm using a Mastr II receiver with no preamp. Interconnect cables are RG142. The old VHF Engineering receiver developed problems not worth fixing, so everything is on the bench for the new receiver and re-tuning.
Desense was always an issue with this repeater, with 1-3db pretty normal. So I decided to re-tune the duplexer. I used a signal generator and receiver. All ports were either terminated in 50 ohms or had a 10db pad in series with the generator and receiver during tuning for minimum signal through the respective halves. It seems to tune well and predictably. However, I'm getting 20db+ of desense with the duplexer operating into a known good dummy load. I can reduce the desense considerably by *winging it* and tuning the cavities while the repeater is operating. (Maybe that's the way I should tune it.......!) So something isn't right. I'm not totally convinced that this duplexer wasn't <played with> at some point, so it is possible that cables in the harness were mixed up. There is no labeling or other info on the duplexer, since the metal box that it was in when new is gone along with the nameplate. So it is not clear which side is which, and I may have been trying to use it reversed (although I don't think so). I believe that this duplexer was originally ordered for 2M, but I could be wrong, which could account for some troubles. So where would I find info on harness cable lengths so I can check them? Or if someone has one of these working on 2M and is willing to make some measurements that would be awesome. And which half of the duplexer is for the high and low frequencies? Laryn K8TVZ
