Gary, I wasn't aware that duplexers *cause* problems- perhaps a duplexer will *solve* your problem!
If we assume that your 2m transmitter is putting out 50 watts and your receiver has a sensitivity of 0.3 uV, you will need around 89 dB of isolation between TX and RX. This can be achieved with about 22,000 feet of horizontal separation between antennas. Since you have less than 1/10 of the required separation, you probably have far less than the necessary isolation for noise-free operation. Gain antennas, if used, will require additional isolation. The fact that pass cavities provide minimal improvement suggests that something else is causing the interference. If the problem just started recently, check to see if someone has put a new transmitter on the air nearby, or if any work has been done on a co-located station. Careless techs sometimes leave off critical shield plates. Also check to see if your link radio is leaking some RF at the input to the last tripler stage- its driver just happens to operate in the 2m band. A good sweep with a spectrum analyzer should uncover any radiators at your receive site. Since you already have a UHF link system, try moving the receiver to a site that is at least 4 miles away from the transmitter site. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Sent: Thursday, May 25, 2006 1:48 PM To: Repeater-Builder@yahoogroups.com 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 quieting, 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/
