Tom, According to my CommShop duplexer isolation calculation software, a 600 kHz split at 2m with a 50 watt transmitter and a receiver with a (my assumption) sensitivity of 0.35 uV, about 87 dB of isolation is necessary to achieve no desense. If you intend to use two antennas, be aware that they will need to be separated by about 202 feet vertically or over three miles horizontally. Neither of these separations is practical for a portable repeater.
Perhaps you should consider a UHF portable repeater, which can use a notch duplexer for the 5 MHz split. However, the ordinary UHF mobile notch duplexer will normally not tune down into the Ham UHF bands without having the internal coupling loops modified at the factory. I once converted a GR300 desktop repeater from the commercial UHF band to the Ham 70cm band, and I had to order a new Celwave factory-tuned duplexer to achieve optimum performance. 73, Eric Lemmon WB6FLY -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Crowley Sent: Saturday, August 30, 2008 11:11 AM To: [EMAIL PROTECTED] Subject: RE: [EMAIL PROTECTED] VHF Duplexer Hello I'm tring to get this done before the snow flies. Looks like two ant. and some space to get it to work also some luck thanks for the info Eric At 10:22 AM 8/30/2008 -0700, you wrote: > > This question is best posed on the Repeater-Builder list > (<mailto:Repeater-Builder%40yahoogroups.com>[email protected] <mailto:Repeater-Builder%40yahoogroups.com> ), > but I know the answer: A mobile (notch) ***************************************************************** Thomas E Crowley KC0VII [EMAIL PROTECTED] <mailto:tecrowley%40iowatelecom.net> http://www.iowatelecom.net/~stagreenhouse/page2.htm <http://www.iowatelecom.net/~stagreenhouse/page2.htm> St. Ansgar, Iowa. 50472 *****************************************************************
