John, I agree with Larry that the problem is that you have transmitter and receiver too close in frequency and in separation distance. I am not an expert, but I think you might try using a couple notch filters; i.e. notch the receive frequency out of the transmitter and notch the transmitter frequency out of the receiver. Also, you could reduce the transmitter power to a minimum acceptable, and you could go to a highly directional antenna for the link receiver. Maybe you could orient the directional link antenna to put the transmit antenna in a null.
Good luck, John T. >-----Original Message----- >From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >buil...@yahoogroups.com] On Behalf Of John Godfrey >Sent: Wednesday, April 29, 2009 5:42 AM >To: Repeater-Builder@yahoogroups.com >Subject: [Repeater-Builder] Linking and interference problem > >I was hoping you can help our club with a repeater link problem. What >we >have are all GE master 2 stuff. Here is what we have going on. we >have >had for years a 147.270 + repeater that works great. > >Last year we added a link into a central state repeater system using >a link radio on >one of our ports. It transmits on 442.025 and receives on 443.2. For >six >months we have used the link fine without problems. Last week we >installed on another port a uhf repeater to be used as a hub for the >north central part of our state to also link to us and the central >state >system. The UHF Repeater receives on 449.750 and transmits on >444.750. >We can link the 270 to either the link to central state or the UHF >repeater hub with no problems, but when we link the 270 to both or >just >link the UHF repeater to the link radio, once the UHF repeater is >keyed >up, the input on the link radio is hearing it so we have an awful >squeal >and intermod back into the 270. > >There is also a pager at the location that I can hear when this >happens but not any other time. Again they work fine as long as both >UHF machines are not in use at the same time. When the 270 is linked >into Central state, even if the UHF repeater is not linked in, if you >key the UHF repeater you here the squeal on the 270. I can see how as >the link input goes out over the 270 when they are linked. I am not >sure why I can also here it on the UHF repeater when I unkey it, even >if it isn't linked in. Other than the last part of that it would make >since to ne that I have the two 440 antennas to close. We have them >about 10 feet apart, but the one can't go higher and the other can't >go lower and still serve the purpose needed. > >I am thinking I need some kind of filter, that I can put on the link >radio, >that will protect it from the transmit of the UHF repeater. In other >words the 444.750 is coming in my receive on the 443.2. Changing freq >is >not an option due to several reasons. If I had a filter of some sort, >that would either allow say 442-443.5 to pass and attenuate >everything >else that would be great. Or something that would pass 442-443.5 and >attenuate everything above 443.5, then that would work. Guys, what am >I >looking for and where might I find it. Must I build something that is >this custom, or can I buy it. If I must build it, where should I >start. >If I can buy it,, where from and what would they call it. > >If my thoughts are off base, please help me to know what other >questions I >need to answer to solve such a problem as this. I thought maybe the >pager was just interfering, but why would the 270 work fine when >linked >to the link radio, or linked to the UHF repeater, and the only time >we >have the problem is when the 270 is linked to the link radio and the >UHF >repeater is keyed up, regardless of whether the UHF repeater is >linked >in or not. > >I know my question is long, but m hope was to explain the >problem with enough detail that you might have an answer for me. > >Your help would be greatly appreciated by our Club. >73 de John Godfrey >KE5NZY BARC Pres. >DISTRICT B ADEC >ASTEN NM > > > > > >------------------------------------ > > > >Yahoo! Groups Links > > > > > >__________ NOD32 4043 (20090429) Information __________ > >This message was checked by NOD32 antivirus system. >http://www.eset.com
