I know, TX separation is not what he was talking about. "RX freq so close to the TX freq of the other repeater doesn't exactly sound like a good engineering practices"
Either RX is 1.2 MHz away from the other TX. So, my reply was accurate. Joe M. Eric Lemmon wrote: > Joe, > > The transmit frequencies are separated by 600 kHz, not 1.2 MHz (147.360 - > 146.760 = 600 kHz), which causes mixing products to fall exactly on the > inputs. > > 73, Eric Lemmon WB6FLY > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of MCH > Sent: Sunday, February 15, 2009 11:19 AM > To: [email protected] > 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 >> >> >> >> >> > > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
