This is definitely emininating from his neighbors TV. It's the screaming
horizonal "sweep" of the TV. Unfortunately this 15.75 khz is so rich in
harmonic energy it can be heard in the HF band. In bad cases this energy is
inductively coupled with the cable TV and then acts as an antenna to make
matters worse. Just put an AM broadcast receiver near any TV and hear how it
sounds at 1 mhz. This can be attributed to the poorly shielded TV's now
produced to keep cost down. Never had trouble like that years ago but it's
the sign of the times...RF junk is amongst us at every turn.
I have had some success reducing this level of backfed RF energy by wrapping
the cable in a large toroid at the input of the TV. I would suggest 2 or 3
FT-240-43's from Amidon tie wrapped together to make a larger core then
pre-wrap RG-6U as many times as you can get it through then put on the
F-connectors. Bring a barrel cable connector and put it in series with his
input. Explain to the neighbor it's a passive filter and will only help
eliminate the RF backfeed.
Subject: [RFI] Anyone heard of this type of noise?
> A local ham started getting a strange noise on HF, only at night. It is 2
> khz wide, every 15 Khz and is audible across 20 through 40 meters.
> Any tips?
> 73 - Scott KA9FOX
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