Joe, the UHF link radio which is the only one receiving the interference, is a GE Master II mobile. The rest are GE Master II stuff as well, but they are what I guess you are calling the station configuration, because we have them rack mounted and the door opens up like a hinge and the components and boards accessible that way. I am just the helper on this project as you can tell, and my knowledge is very weak on this issue. At the moment the problem has been minimized to a large degree based on setting the squelch as tight as it will go, and the receive signal still breaks the squelch and the interference can't. However when the receive signal drops, you can still hear the sound for like 50ms on the squelch tale. The person who does our repeater work KD5HPK could answer any questions about the equipment much better than I could, but his request to me was to try to find a narrow notch filter for the frequencies as per the original email. I added the dialog in the original email, so you guys could help me determine the best approach. I know it seemed like a lot of rambling. I have no way to know what all is on the site as it has maybe 15 antennas on the tower that I don't even know who they belong to. It is a commercial tower site with many systems and even different buildings that we don't have access to. We have identified however that we only get the feedback when both our UHF units are active and no other time. We also can link either on into the 2 meter repeater with no problems. We have duplexers on both repeaters of course and not the link radio as it isn't full duplex. The reason we are tied to those frequencies is that we are linked to several other repeaters and in one direction the UHF Main hub is 75 miles away and they can't change there frequencies because several are linked into it. In the other direction folks link into our UHF repeater from 50 miles away and that freq is set due to the fact that those guys have all their equipment configured for that frequency. So to make the long story short we are the link in the middle. Repeater pairs in our location are not easily changed due to what I have mentioned, plus there are not a lot of them left to coordinate anyhow. If we can just keep the transmit of the UHF repeater out of the input on the link radio.. problem solved. We have proven that with the squelch method, and while that will work for now. We don't like the little dirty squelch tale as it doesn't sound perfect, and don't we all strive for perfection (-: I think the right kind of filter would make it perfect, but I am not sure of that,,, where to find one,, what to call it,, or how to build it.. That to me seems to be the question.. If I am asking the wrong question.. Please just overlook my lack of knowledge on the subject. I build a great amplifier, repeaters are just not my strong suit yet, but I am starting to learn it.
73 de John Godfrey -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe Burkleo Sent: Saturday, May 02, 2009 12:07 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Linking and interference problem john, Forgot to ask in my first reply. I am assuming that your link radio is also a Mastr II from your original post. Is it a mobile or a station configuration? Thanks, Joe --- In Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> yahoogroups.com, "John Godfrey" <ke5...@...> 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 >
