In the early '70s we had a repeater made up with GE Prog line strips running 60 watts installed on an old rusty sheriff tower with non-insulated guys. On a foggy morning we would always hear radio station audio when we keyed the repeater. We traced the station audio to a site over 75 miles from our repeater, but the station operated on 600 kHz. The rusty guy attachment to our tower gave a nice rectifier to produce the mix + and - our transmit frequency, and gave rise to the BC station audio on our transmitter. We were unable to get rid of this problem for as long as we used the site. Thankfully, a foggy morning was a rare occurance and we were able to live with it a few days a year.
Sounds like you have the source of the 600 kHz signal located, but now you need to figure out the point of the mix. Your transmitter, his transmitter, or some rectifying joint on your tower or nearby. I recently decided not to place a repeater antenna on the side of a tower erected on top of a water tank in favor of a location lower but much further from the guys for the tower. I was afraid of the problem with the non-insulated guys in the near field of our antenna. 73 - Jim W5ZIT --- On Sun, 7/6/08, Pete <[EMAIL PROTECTED]> wrote: From: Pete <[EMAIL PROTECTED]> Subject: [Repeater-Builder] Interference / Intermod ? To: [email protected] Date: Sunday, July 6, 2008, 10:23 AM Hello, Looking for some help or advice on a problem. I started get a "squealing" sound on my VHF repeater a while back. It was not consistent so it was hard to try and track the source. Well I found out a few days ago what the problem was. First let me fill you in on the Repeater. Motorola MSF5000 VHF @ 200 watts (its a 425 watt repeater) TX/RX 4 can cavities (about 2 yrs old, bought tuned from TX/RX) Cellwave StationMaster VHF Antenna @ 380' Andrews 1-5/8" Hardline from the Duplexers to the Antenna Second Repeater (backup) Motorola MSR2000 VHF @ 107 watts Wacom BpBr 4 can cavities Here's the issue. There is a new repeater, that came on the air, at the same time the "squeal/intermod" came on my repeater. My repeater is on 147.285 with a tone of 118.8. His repeater is on 146.685 (600khz lower then mine) about 20 miles away. His TX antenna is up at 155' Every time his repeater keys up, and mine keys up, the intermod noise is there, until his repeater drops, then it goes away. At first I thought it was HIS repeater causing the issue, which in a way it is, but I figured out it is not entirely his fault. I tried the other repeater, with the TX/RX cavities, and it still did the same thing. I tried the WACOM cavities on both repeaters, and still, the same issue. Now I can go outside the repeater site, in my car, and key up on 146.685mhz, and produce the same issue. I tried turning the power back to 100watts on the MSF5000, but still have the same issue. The only other test I have done, is put the MSF5000 in Disable, and when his repeater keyed up, I forced the MSF5000 into transmit, and the issue was not there. I dont have access, to any high end test equipment anymore. This repeater worked flawlessly for many years, until this issue came up. My question is... has anyone else experienced a problem like this> Does anyone have any ideas for me to try to solve this issue, shy of me changing the repeater frequency? I already talked with this gentleman, and he has no interest at all, and changing frequencies back to 146.985... where he was. Thanks in advance to any help. 73, Pete K4QHR _
