John, The procedure is primarily measuring the site noise in your system, not desense. It simply measured first the receiver sensitivity then connected the antenna and did the same.
For the desense test we are looking to see the noise caused by the repeater transmitter although site noise can be part of this noise. In step 3 of the test one would key and unkey the transmitter to see the defferent effects. I think the test suggest the transmitter is keyed at all times. Not unkeying/keying the transmitter would give you the noise results, but not tell you if the noise is from the transmitter or some other source. The test is effectively telling you the site noise with all connected which is important. However, to determine if you have desense from your repeater you need to key/unkey the tx. Step 1 can be removed for would think you have done this before, know the receiver sensitivity. Doing the same with the T on the duplexer output with the tx unkeyed would be your starting reference for the receiver, then keying it would give tx noise level. If you connect all in and do steps 2 & 3, but keying and unkeying the tx in step 3 is what you want to do for tx desense. We are looking for desense, not site noise in your case. Site noise is important, but often one can do little about it for it comes from many sources inclusing 100 transmitters within 10 miles of you. 73, ron, n9ee/r The test in the link is a must for repeaters and is a good one. >From: Mike Morris WA6ILQ <[EMAIL PROTECTED]> >Date: 2008/07/10 Thu AM 03:55:04 EDT >To: [email protected] >Subject: Re: [Repeater-Builder] Measuring Desense > >At 12:18 PM 07/09/08, you wrote: > ><<...>>Ron, Don, Mark, and others, > >The attachment shows how I think I should connect things tomeasure desense. I >would use the Bird with sampling coupler in place ofthe iso tee shown. Does >this appear to be a correct way to measuredesense? > >Also, I can replace the feed line and antenna with a dummyload as Ron has >explained. > >John AF4PD ><http://www.repeater-builder.com/tech-info/effectivesens.html> > >Mike WA6ILQ > > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
