A similar war story from back in the early 90's...Commercial customer with a 35MHz base complaining of dramatically reduced range. Base and mobiles checked out fine, antenna system fine, just trouble receiving the mobiles. Dropping the PL with the antenna connected I noticed what seemed to be a constant carrier. A bit of wandering about with a scanner using increasingly short lengths of wire for antennas brought me to a nearby house. The noise seemed to be radiating on the telephone line and the power line. The house was a rental owned by the company with the radio so after proper contact was made an inside sweep found the ... telephone answering machine!?!?!?!
The device was powered by a wall wart supply with an very long cord (getting any clues yet?); which had recently come back from a repair center. The wall wart had a slightly audible hum. A snap together ferrite with as much of the excess power wiring wound onto the ferrite as possible, and another ferrite on the telco line brought the noise to a level that was not detectable at the base station. Milt N3LTQ ----- Original Message ----- From: neal Newman To: [email protected] Sent: Friday, December 26, 2008 9:39 AM Subject: Re: [Repeater-Builder] Six Meter Repeater Noise Issues Noise on the six meter repeater. On my machine 53.67 in New jersey I was getting noise that was holding the machine Keyed up. then drop. and key up again. I thought it was desense Even with a big expensive Commercial Duplexer. with the transmitter off, the normal unsquelched Hiss sounded Fine No noise that we could detect. after weeks of this. We finally found out what the Problem was. the 2 meter,and 440 machines next to it ran just fine.however They both had an IRLP link on them. The Noise problem turned out to be the Router/switch. The Noise it was creating was just at the threshold level to Key and hold open the repeater. BTW. The 6 meter machine was in PL with a Tone of 67hz...... Not a good choice. between the60 cycle noise of a bad wall wart for the router switch and the noise it created. might as well put a flea power transimitter with PL sitting on the repeaters input. changed the router swich and PL tome. and Problem wentt away. Verizon uses cheapo routers. we placed the new one in a shielded box Neal-KA2CAF --- On Thu, 12/25/08, Mike Morris WA6ILQ <[email protected]> wrote: From: Mike Morris WA6ILQ <[email protected]> Subject: Re: [Repeater-Builder] Six Meter Repeater Noise Issues To: [email protected] Date: Thursday, December 25, 2008, 10:12 PM At 11:06 AM 12/25/08, you wrote: Hi To All & Hope everybody had a good Christmas, While the subject was brought up, I have been having a similar experience here at my location. It is not on a repeater, but a simplex radio (vertex VX3000l mobile) for a base on the natl Red Cross freq of 47 mhz. In the daytime the receiver is quiet and hears fine. It seems as about the time the sun starts going down, the receiver's squelch opens and has a constant static noise for many hours but still receives fine. It may do it all night, I don't know, I haven't stayed up to see, just leave the radio on and go to bed. Was wondering if could be power line noise (but why wouldn't do in daytime also)? Is there any interference to the HF bands like this at night? Thanks, Mike KB5FLX An old trick - if the on-time changes about 6 minutes a day then it's light-dependent (i..e a photo-electric triggered yard light). In your shoes I'd power the radio from a gell-cell, and then go flip breakers off one at a time. That will tell you if the noise source is inside the house, and if so, on which breaker. Mike WA6ILQ
