Sir, I read your FAQs and did not come across anything that can relate to my RFI problem, but perhaps you can help. I book marked your page in case I do come across some telephone interference, etc. I just purchased a FT1000MP a month ago and started listening and doing some minor operating. I have been out of the hobby for about 15 years and was hearing quite abit of noise internally to my QTH, so I began an investigation. I enjoy 10M, so I was keenly aware of S-7 strength signals at various places. I tracked these down to VCRs. I tracked some S-2 stregnth signals down to the doorbell transformer, and another S-7 signal to a cordless phone. I had a number of 15.75 Khz space warbles across much of 10M, 15M and 20M, tracked these down to my own TV set upstairs.. :) So low and behold I felt I had it all figured out. The thing was that I still had S-3 to S-7 bursts of static on all the bands. These occur consistantly every 3 to 4 seconds, and a consistant buzz during the burst. You can see the S meter rise and fall consistantly with the burst of static. The noise blanker takes em out, but what could they be? I had all the circuit breakers in the house turned OFF except for the one that fed the HF rig and still had the static bursts. (This was all done very late at night, everyone in the neighborhood had hit the sack, so no TVs and other items were on) I went outside to see if I could see anything periodic in nature, and there it was, a large FM tower on the horizon that had flashing red lights, very tall 500 feet?. They seemed to flash at exactly the same rate of what was being experienced on the HF rig. Well, with that seeming to be the problem, I went to bed! I got up in the morning and the tower lights did not appear to be on or pulsing, but the same interference was present in my receiver. It seems to strongest on 18 Mhz, varies in strenght on 10M and is present all the way down to 160M. The power distribution system in the area is all underground, no overhead power, CATV or telephone lines. Is there any record of these types of lights on a tower causing RFI to Amateurs? Or am I missing something else in the neighborhood. During the day also? Could I still be receiving something through my 120 volt connection, even if that was the only circuit on? I guess the only way to check that would be to get a DC supply and hook er up. I have poured over the ARRL RFI handbood, no mention of tower lighting interference, just abit about neon. Thanks in advance for any ideas or suggestions.... Mike

Mike, Thanks for the interesting inquiry. Well, you have been busy. I'm not sure what kind of bulbs they use for the commercial radio tower. A call to the station engineer to inquire if there is a faulty connection etc. would not be innapropriate. It also could be coincidence that the tower light seems to be in time with the interference. Don't overlook lights that are controlled with a photocell for generating lots of funny noise. Also, if you are close to any store displays, such as things that move back and forth with little motors, that could be a source. Don't forget the obvious flashing neon sign. Since you said the interference was on all bands maybe you could get a small inexpensive portable handheld am radio ( I think Radio Shack has them for about ten bucks). They are very directional on am broadcast band and you could snoop around the neighborhood with one of them. Since the interference is at night and is periodic in nature, I would suspect some kind of flashing light or sign however. Anyway, good luck to you and if you figure it out I would be interested in knowing. Sincerely, John

Well John, thanks for your reply. Shortly after I sent you the email, I did some more experimenting and drove my car around town with the AM radio on. And lo and behold, the two light poles near my house were creating the static. You hit the nail on the head when you said look for photo cell controlled lighting in the area. The thing is that the interference is on day and night, even when the lighting is not on. I drove under other lights in the area and no interference there. Our area is a new housing development and i suspect that these light poles were put up as temporary structures. It was a true coincedence that the tower lights were flashing at the same rate. Now I dont know what to do except call the Municipal City Electrical folks, I suspect at bad capacitor possibly charging and arcing to ground? Do you have a suggestion? Thanks again - 73

Mike, Recently I was inundated with about 300 e-mails and yours must have gotten lost in the pile. I just found it today. Well I'm glad you tracked down the source of the QRN. I don't really have any better suggestions other than calling the utility company. They usually are quite responsible in fixing those types of things especially when reminded that it is illegal to broadcast radio signals (ie. QRN) without a license. In the past, some amateur radio op's I know have gone so far as to hit the pole with a sledge hammer. Some of them swear that this fixed their problem! Of course I would not recommend that. Let me know if and how you get the problem fixed.
73 es dx.

Click on the picture for RFI filter construction.

RFI Related Links:

American Radio Relay League RFI
Ground Loop Problems
More RFI Links!


Related Links

Partner Links