Doug, Please advise the make, model, and power of your transmitter, and the make and model of your receiver and duplexer. That information will help the Elmers on this list arrive more quickly at possible causes. It will also be helpful to state the make and model of your antenna, and the type and length of the feedline. What is the transmitter power output (before the duplexer) into a dummy load, and what is the 12dB Sinad sensitivity of the receiver? I hope that the jumpers are all double-shielded cable, such as RG-400 or RG-214; are they?
The MFJ antenna analyzer is really useful only to measure the VSWR of the antenna, by itself. Correct tuning of a duplexer is best done with a network analyzer, measuring return loss. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> [mailto:Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of Doug Hutchison Sent: Friday, June 12, 2009 8:26 AM To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> Subject: [Repeater-Builder] Trying to test my antenna system (suspect desense..) Suffering from poor receive perfomance and am trying to check integrity of system. Single 3 dB antenna, single output 6 cavity filter, 10w out of filter. Could someone enlighten me, the cavities are factory tuned 145.6875 tx 145.0875 rx and am attempting to check VSWR with an MFJ antenna analyser. The answers I see do not conform to my understanding so, at what frequencies, at the input and output of the filter while connected to antenna, should I see low vswr. I'm seeing 1.2:1 or so at 146.08, should I not see that on 145.08? Just a bit confused! Thank you, Doug - MM0BJA
