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75 Meter RFI Problems

Nov 4th 2011, 05:28


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I have recently encored strong interference from what I believe to be and outside source of RFI. I also notice this on my AM broadcast AM radio. IT seems to peak around 3.9 MHZ but can be pick with less intensity a various apparently unrelated frequencies into the 80meter portion of the band. This is reading about 20 to 25 DB over nine on a Kenwood TS-850S Transeiver using a shortened inverted V for and antenna. I also pick this up on my beam on the same band and appears omni-directionsl. Does any of the Cable TV networks operate in the range anymore? Any siggestions would be appreciated before I go to the utility company. I have tried turning off various lights, etc in the house to no avail. Also using a dummy load it completely goes away.
Dec 28th 2011, 19:05


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
This sounds like it might be a consumer device of some sort. Most likely it is located either in your home or a nearby residence. Typically, based on the signal levels that you report, the source will be within a couple hundred feet of your antenna.

Note: Because the noise varies with intensity as you tune across the 80 meter band, it is unlikely to be power line noise. Your power company is therefore not responsible for either finding or fixing the noise.

The first thing I would do is turn off the main breaker to your residence while listening to the noise with a battery powered radio. If the noise goes away, you can further isolate the source by hitting the individual breakers. Once you know the circuit, try removing devices on that circuit to find the culprit.

If the noise source is not in your house, it is likely in a nearby residence. Often times, the source is in an adjacent residence or on the same power transformer secondary system as the complainant. You can use this procedure on the RFI Services Web site to find the source:

Additional locating information can be found in the ARRL RFI Book and the 2012 ARRL Handbook.

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