A total insertion loss of about 1.0 dB works well, in my experience. With two 8" bandpass cavities in series, this gives at least 25 dB of isolation from the transmitter carrier at a 600 kHz split.
Bear in mind that your notch cavity has the same deficiency as the typical BpBr duplexer- there is relatively little bandpass effect. A pass-notch cavity is a poor substitute for a bandpass cavity. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Pointman Sent: Thursday, November 26, 2009 10:09 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: pre-amp placement So what is the recommendation to set the loss of the BP cavity? I have a setting as to 3 dB, 1 dB, .5 dB etc. Running the ARR preamp on a UHF repeater, it seems the preamp is a little too much and we get a little desense. I am only running a 4 cavity duplexer and a notch cavity with the preamp. de KM3W
