Eric, The repeater is 70cm amateur (444.625 TX/449.625 RX). These duplexers have been used on this same repeater for I'd say 10-13 years. I was given the repeater by the previous owner because the site was lost and he did not have time to repair the problems that did show up (the PA went out). I had a mobile PA that I turned down and used it and ran the repeater from my house for a few months (ran fine), then disconnected it. It sat in my shop from Oct 2008 until around 1 month ago. It was not as before. I wound up basically rebuilding the receiver, and I rebuilt the original PA. However, this year in Oklahoma, we did get a lot of rain and it did get pretty warm in my shop (along with high humidity. I wonder if the heat and humidity might have done something to the duplexers. I do have another set of these that were on the link transciever (the link was set up to run full duplex as well), I may retune them to see what I have.
Equipment and tuning method. Here is what I was taught how to do it. I use an IFR 1200S service monitor, and the only spare radio I have at the moment is an Icom T7H HT. I start with RX (449.625) first. I connect the IFR to the antenna port, a reciever on the RX port (high pass), and a dummy load one the TX (low pass). I adjust RX pass freq for best SINAD. I then change the receiver and IFR to the TX freq and adjust for the best rejection, or worst SINAD. I do the TX (444.625) side the same way, best SINAD TX pass, worst SINAD RX reject. I tuned a set of duplexers this way before on a 2m repeater using 6 cavity Sinclair BpBr with no problems, this is the first I have messed with a set of Wacom's. Terry KM5UQ ________________________________ From: Eric Lemmon <[email protected]> To: [email protected] Sent: Saturday, September 19, 2009 6:30:57 PM Subject: RE: [Repeater-Builder] UHF Duplexers Terry, Is your repeater in the 70cm Amateur band? If so, and your WP-678 duplexer was not originally tuned for that band, that may be where the problem lies. I have a Remec-Wacom WP-678 duplexer that I bought from the factory for GMRS service, and its insertion loss at the transmit frequency is 1.14 dB, equivalent to 38.5 watts out for 50 watts in. Your duplexer's measured insertion loss exceeds 4 dB. Most Wacom UHF commercial-band duplexers will tune down into the Amateur band, but not all of them. It appears that your duplexer is tuned improperly, or it may be impossible to tune it to your pair. What method and equipment are you using to tune the duplexer? 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@ yahoogroups. com [mailto:Repeater-Builder@ yahoogroups. com] On Behalf Of terry dalpoas Sent: Saturday, September 19, 2009 2:11 PM To: Repeater-Builder@ yahoogroups. com Subject: [Repeater-Builder] UHF Duplexers Just about finished with the Mastr II UHF repeater. I've run into a problem with the duplexers. They are a set of WACOM BpBr Model WP678. I am putting 48W into them, but only 18.5W out. I believe this should be better. RX will open squelch at around .2-.3 uV through the cans (this I know is OK). Could there be a problem with the TX side of the cans? Terry KM5UQ
