Because of the internal desense issue, I'd build them the same, but operate the two radios separately. That is, use one as a transmitter and the other as the receiver by default. No duplex mods required. If the Tx dies on one, swap the system cables around to make the formerly-transmitter radio the receiver, and vice-versa. You could even automate the changeover via a couple of coaxial relays and some simple homebrew transistor and/or relay logic tied into your controller.
--- Jeff WN3A > -----Original Message----- > From: Repeater-Builder@yahoogroups.com > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Plack > Sent: Monday, April 26, 2010 1:49 PM > To: Repeater-Builder@yahoogroups.com > Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters? > > > > ? > Tim, > > My plan at this point is to convert them to full duplex, so I > can use the second Mitrek to prepare a complete, plug-in, > standby set of RF decks. The mods look very straightforward, > but I was wondering if there were any gremlins people discovered. > > Your heatsink approach, however, is exactly what I was > talking about. I have several very large heatsinks originally > designed for use with big SCR switching circuits which look > to be more than generous for a 30w PA at 100% duty cycle. > > My first repeater was built from a 2w Repco exciter board > repurposed from RFID service. It was supposedly rated for > continuous duty, but had to run very hot to dump the heat it > produced through the little aluminum tab mounted to its own > PC board within the case. I fashioned a new tab with a 90ยบ > twist which allows sinking the little PA to the case itself, > and it never got above "warm to the touch," even after hours key-down. > > Guys, I appreciate all the input. > > 73, > Paul, AE4KR > > > ----- Original Message ----- > From: w7...@comcast.net <mailto:w7...@comcast.net> > To: Repeater-Builder@yahoogroups.com > <mailto:Repeater-Builder@yahoogroups.com> > Sent: Monday, April 26, 2010 10:16 AM > Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters? > > > > > > Isn't the rpt. going to be built using (2) Mitrex, thus > shielding should not be a problem. I have, in the past (with > the help of a Bridgeport mill), fashioned "Larger Heatsinks", > that bolt onto the orig. Mitrex heat sink....seems to > dissipate heat well... > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.801 / Virus Database: 271.1.1/2792 - Release > Date: 04/26/10 02:31:00 > > >