Mike,
I had read this article but I have not followed the procedure to get a measure of the RF noise floor. This would be worth while. I believe I can and will do this. I had suspected inadequate duplexer operation, and this still seems likely, and the article you suggested does not include the duplexer, so I had not bothered with it. I can measure the attenuation of my isotee so measurement of the noise floor should be easy. Thanks, John -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Morris WA6ILQ Sent: Sunday, August 03, 2008 3:46 PM To: [email protected] Subject: Re: [Repeater-Builder] Re: Measuring Desense John might find this article interesting... <http://www.repeater <http://www.repeater-builder.com/tech-info/effectivesens.html> -builder.com/tech-info/effectivesens.html> Mike WA6ILQ At 09:56 AM 08/03/08, you wrote: >Right on the money Scott... many times the antenna and/or >feed line can be the trouble maker. Although not practical >in many cases... a 50 ohm test termination at the top end >of the feed line can tell you a lot... > >Knowing the "effective sensitivity" at the site is a big deal >often overlooked by the more informal repeater owner/operator. > >cheers, >s. > > > "Scott Overstreet" <[EMAIL PROTECTED]> wrote: > > > > John--- > > I don't know if you have done the following yet but if not > > you should. Put an iso-T in front of your receiver and do > > a simple desense test using your signal generator into > > the iso-T. Set the generator for a couple of kc, deviation > > at 1 kc so that you can easily recognize it. Run the signal > > level down to where you can just hear it in the receiver > > with the transmitter off. Turn your transmitter on. Do you > > still hear your generator signal? Lets assume you don't as > > if you do you don't have desense. > > > > Now, remove your antenna feedline from your duplexer and > > put a good screw on dummy load in it's place and repeat > > the above test. Do you still have desense? If yes, you > > have insufficient duplexer performance to support your > > transmitter (power and sideband noise spectra) or leaky > > interconnect cabling. > > > > If no, you are getting desensing from either your feedline > > or your antenna or something your antenna radiated signal > > is exciting like a rusty tower joint or joints which is > > or are producing wideband noise which your antenna is > > hearing and feeding back to your receiver as a desensing > > signal. If this looks to be the case, put the dummy at the > > end of your feedline in place of your antenna and repeat > > the testing. This should leave you with either a feedline > > or connectors to replace or a possibly bad antenna. > > > > I've been this far and found a corroded Hustler. Took it > > down, cleaned it up and put it back as a replacement was > > not immediately available----it is still up and working as > > well as it ever did with absolutely no desense. > > > >------------------------------------ > > > >Yahoo! Groups Links > > > __________ NOD32 3192 (20080616) Information __________ This message was checked by NOD32 antivirus system. http://www.eset.com
