John, Haven't seen the Guru's jump in here so thought I'd make a comment.
From what I gathered reading your post it appears you have a UHF RX & TX operating with a 1.55 Mhz separation between the 2 units. Bad enough the small frequency spread but having the TX and RX antennas setting in the same horizontal plane 10 feet apart as the UHF repeater transmits (unknown power) into your link receiver has got to be a source of desense/feedback. You didn't comment on any existing filtering for the system ?? I am not a person who has the knowledge to advise about different options of filter/duplexer's available and their effects on your operation. However even with my limited experience I would seriously look at relocating one of the UHF antennas. Either to another location or at a minimum to a different vertical plane. Larry - N7FM John Godfrey wrote: > 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 > > > > > > > >
