Jeff, Best I can tell the connecting harness is good. I may try the set meant for the link radio and see what they do. How do I tune for maximum return loss? If it is better, you can contact me off the group, so it does not get tied up.
Terry KM5UQ ________________________________ From: Jeff DePolo <[email protected]> To: [email protected] Sent: Sunday, September 20, 2009 10:16:59 AM Subject: RE: [Repeater-Builder] UHF Duplexers You should be tuning the bandpass for maximum return loss, not least insertion loss. I've found that older Wacom duplexers develop center plunger contact problems as they age. I trashed quite a few 900 MHz duplexers and combiner cavities because the insertion loss was intermittantly high; the poor center plunger contact was very obvious when tuning them - they were "scratchy" and it was very obvious when the trace on the VNA while adjusting the tuning rod. I guess you've checked the obvious - look for a bad connector in the harness. --- Jeff WN3A > -----Original Message----- > From: Repeater-Builder@ yahoogroups. com > [mailto:Repeater-Builder@ yahoogroups. com] On Behalf Of terry dalpoas > Sent: Saturday, September 19, 2009 8:58 PM > To: Repeater-Builder@ yahoogroups. com > Subject: Re: [Repeater-Builder] UHF Duplexers > > > > 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 <wb6...@verizon. net> > To: Repeater-Builder@ yahoogroups. com > 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%40yahoog roups.com> > [mailto:Repeater- Builder@ yahoogroups. com > <mailto:Repeater- Builder%40yahoog roups.com> ] On Behalf Of > terry dalpoas > Sent: Saturday, September 19, 2009 2:11 PM > To: Repeater-Builder@ yahoogroups. com > <mailto:Repeater- Builder%40yahoog roups.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 > > > > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.409 / Virus Database: 270.13.78/2347 - Release > Date: 09/20/09 06:22:00 > > >
