Again, I know. Respond to AJ's post. He is the one saying 1.2 MHz is too close for a TX to be to a RX that is 'only 18 miles away'.
Joe M. Gary Hoff wrote: > */Has nothing to do with the spacing, but with the intermod/* > */products generated by the two transmitters exactly 600 kHz apart/* > */generating spurious signals on the inputs of the receivers./* > */Gary - K7NEY/* > > ----- Original Message ----- > *From:* MCH <mailto:[email protected]> > *To:* [email protected] > <mailto:[email protected]> > *Sent:* Sunday, February 15, 2009 12:19 PM > *Subject:* Re: [Repeater-Builder] Re: Help with intermod between > repeaters. > > 18 miles apart and 1.2 MHz separation? How far apart do you want to > space repeaters? I know of repeaters only 210 kHz apart at the same > site > that work fine. > > Joe M. > > AJ wrote: > > When were these two repeaters coordinated? RX freq so close to > the TX > > freq of the other repeater doesn't exactly sound like a good > engineering > > practices, even with 18 miles between the two sites... > > > > On Sun, Feb 15, 2009 at 9:37 AM, Gary Glaenzer > <[email protected] <mailto:glaenzer%40verizon.net> > > <mailto:[email protected] <mailto:glaenzer%40verizon.net>>> wrote: > > > > well said > > > > > > > > ----- Original Message ----- > > *From:* Gary Hoff <mailto:[email protected] <mailto:k7ney123%40q.com>> > > *To:* [email protected] > <mailto:Repeater-Builder%40yahoogroups.com> > > <mailto:[email protected] > <mailto:Repeater-Builder%40yahoogroups.com>> > > *Sent:* Sunday, February 15, 2009 10:33 AM > > *Subject:* Re: [Repeater-Builder] Re: Help with intermod between > > repeaters. > > > > */This is one of the toughest intermod products to solve. 2 > > transmitters/* > > */600 kHz apart generate spurs every 600 kHz on both sides of each/* > > */transmitter. When we were co-ordinating repeaters, it's one > > parameter/* > > */we always looked at, and tried to keep nearby repeaters off of > > that/* > > */600 KHZ separation boundary. Are Both repeaters having > > problems or just yours?/* > > */These signals don't even have to be generated in your equipment,/* > > */I've seen them generated by stuff externally and if you look > > at a /* > > */spectrum analyzer when both transmitters are on the air, > > you'll see/* > > */the Christmas tree like display showing the spikes every 600 > > kHz decreasing/* > > */with amplitude as they get farther away. Most suggestions > > made may/* > > */help and all I can say is good luck, the only real way out of > > this/* > > */problem may be a frequency change for one or the other machine.]/* > > */Gary - K7NEY/* > > > > ----- Original Message ----- > > *From:* wa5luy <mailto:[email protected] > <mailto:wa5luy%40cablelynx.com>> > > *To:* [email protected] > <mailto:Repeater-Builder%40yahoogroups.com> > > <mailto:[email protected] > <mailto:Repeater-Builder%40yahoogroups.com>> > > *Sent:* Sunday, February 15, 2009 6:15 AM > > *Subject:* [Repeater-Builder] Re: Help with intermod between > > repeaters. > > > > Thanks to all for your replies. > > > > Joe M wrote > > "You need to reject the opposite TX on each repeater. Your BP > > filters were set wrong. You rejected the RX on the TX side - > > something the duplexer should be doing already. You need to > > install > > them in the repeater and reject the other TX. IOW, install a > > filter > > in the .16 repeater and notch the .36 TX. A good duplexer > > should do > > this as well, but many don't." > > > > Joe that's what I thought I did. Maybe I did not make myself > > clear. I > > put a BPBR cavity rejecting 146.76 and passing 147.36 > > between the > > repeater transmitter and the duplexer at the 147.36 > > repeater. This > > is where I was surprised that the mixing got worse. If I put > > the > > cavity in the wrong place let me know. > > > > Eric Lemmon WB6FLY wrote > > "The first question that enters my mind is, were both Micor > > stations > > originally built as repeaters, with the extra filters and > > shielding > > plates,or are one or both base stations that have been > > converted to > > repeaters?" > > > > I built our repeater. It's the 146.76 machine. It was > > originally a > > pager TX. All shielding and the lo pass TX filter is in > > place. I have > > looked at it with a spectrum analyzer and see no other > > signal than > > 146.76. I have no idea as to what the other repeater was > > made from. I > > will take a second look at their TX. The next time I go down > > there I > > plan to take a 50 watt radio and connect it to their > > duplexer to try > > to eliminate or prove their PA has a problem. > > > > "The second question is, > > are either or both repeaters equipped with ferrite isolators?" > > > > The 146.76 has no isolator. The 147.36 has a brand new, I > > believe > > Sinclair, isolator that was factory built for this > > frequency. The > > isolator has no affect on the problem although I don't think > > it's > > installed properly. I did not notice when I was there but I > > think > > it's mounted on a steel plate. Also there in no cavity > > between it and > > the duplexer. The mixing is there with or without the > > isolator in > > line. They paid big bucks thinking this would fix the > > problem. By > > the way they also replaced their antenna and feed line which > > may have > > made the mixing worse. > > > > John wrote > > "I hate to tell you, a definite way to eliminate > > the problem, is a frequency change so that the > > output of the two transmitters are no longer not 600 khz apart." > > > > Funny that`s the first thing I told them. I am familiar with > > two > > pagers 600 khz apart and the havoc that can be raised. > > > > I plan to go back down there when I have time and let the > > group know > > what I find. > > Again thanks to all. > > > > ---------------------------------------------------------- > > > > > > > > Checked by AVG - www.avg.com <http://www.avg.com > <http://www.avg.com>> > > Version: 8.0.237 / Virus Database: 270.10.23/1953 - Release > > Date: 02/14/09 18:01:00 > > > > > > > > > > > > > >
