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Author Topic: 160M RFI from CATV?  (Read 1328 times)
N3PM
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Posts: 31




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« on: January 03, 2007, 06:49:09 PM »

 I have just started experiencing interference on 160M. It's a buzzing that the NB will partially take care of, and runs exactly 18 seconds on, and 18 seconds off. I could get it down with an active phasing type noise canceller, but decided to try tracking it down. I used a portable radio, set on 1813, and found the noise on the AC wiring. Going to the meter, it was stronger. The phone, cable and meter are all in the same area. Wow, it was strong on the phone wires, and strongest on the cable feed. At the pole it was the strongest. The pole has all three drops for me on it. On my neighbors house, only the cable has the noise on it.
 Back at my house, with the power cut, and the phones disconnected at the box, it was still there.
 Two questions - do the cable systems use anything around 1.8 mhz, and what's your results in dealing with cable techs regarding these problems?
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N8BOA
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Posts: 97




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« Reply #1 on: January 06, 2007, 07:44:20 AM »

I am also looking for a noise on 160M (20db over S9)  and with the am radio like yours it seems to be comming from the CATV or power lines when I hold the radio next to them. But be carful, this maybe the am radios antenna coupling with the sheild or wire resulting in a larger antenna making the noise louder. In my case I think it is my neighbors water well pump as they have a varible frequency motor controler on it. But I need to do more investigation.

 As far as the CATV I heard they use a square wave ac to send power down the coax to power the amplifiers on the line. I could see how these could be a source of noise. But one would think that would be a continuious noise. Since your noise cycles on and off maybe it is some type of heater or like a hot tub
Good luck
Sean    
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N3PM
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Posts: 31




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« Reply #2 on: January 06, 2007, 09:13:40 AM »

GA Sean. I found the noise is only there after 5 PM or so and haven't had a chance to stay with it past 11 PM. I spoke to the cable tech and they'll have someone out on Monday. We talked about line amp power and the battery back ups they use. I have seen battery chargers that have cyclical noise, but the period  changes with the amount of charging the battery needs. I tried to come up with stuff that would run that way, and the list gets short when it comes to the 18 second cycles. I'm leaning towards the noise is just "riding" the cable shield from who knows where.
I'll have to take the radio and walk my dog for a few evenings.
73 Mike AD1OS
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N3PM
Member

Posts: 31




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« Reply #3 on: January 07, 2007, 06:00:12 PM »

Found it. Took the schnauzer and the portable radio for a walk and located a "security" light on a utility pole, about a half mile away. It tries to start for 18 seconds, and shuts down for an equal time. Odd thing is, there's no considerable noise on the poles going in one direction, only towards my street.
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