Gary: First; get some test equipment out to the Rx site. Is the noise there when you receive a signal with out the link bringing the Tx up or only when you let the link key up the Tx? The horizonal isolation at 2M between dipoles is approximately 70 db. You didn't say what type antenna you had for a Rec ant. The 6db gain on the Tx antenna will decrease the isolation to approximately 64 db. not enough for a repeater system. If the noise is there only when the 2 m Tx is keyed up, the put a single notch cavity on the Tx to notch out the Tx noise, it may be necessary to also place a single notch cavity at the Rx site to improve the Tx freq isolation. You did not say anything about the Rx site. What else is there? If the noise is there without the 2M Tx being keyed up, now you have some other external source of the noise. You may have a simple intermod or a high order mix causing the noise. Get a good Spectrum Analyzer and start hunting. Fred W5VAY
----- Original Message ----- From: "Gary" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, May 25, 2006 3:48 PM Subject: [Repeater-Builder] White Noise on Two Meters..... >I have an interesting thing happening on our two meter repeater. We > have what appears to be a blanking white noise that is present on the > input. The repeater is a split site system with a 440 link from the > two meter receiver site over to the transmitter site about 2000ft > away. There are no duplexers in the system to cause problems. > > The link on 440 is clean of any noise, so we are quite confident the > link is not a problem. > > On two meters, when a signal is anything less than full quiteing, we > get a white noise that will almost mask the audio. We have tried > different receivers such as the GE MVS and now a GE Master II. We > have removed the preamplifier with minimal results. The receivers > have excellent sensitivity and the tuning process of the receivers is > correct. We have also tried putting pass cavities ahead of the > receiver with no appreciable change. The antenna is a DB-224 mounted > on a broadcast tower just below the bays of an FM broadcast > commercial transmitter. We have turned OFF the fm broadcast > transmitter at times to check if perhaps this was the problem but no > change was noted. > > ANY IDEAS from anyone??? > > THANKS! > Gary - W5GNB > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
