It is possible that the RFI he is receiving is radiating from the Cable
equipment and not originating from it. Cable TV Equipment, in my experience,
doesn't radiate such a broad banded signal. However, the equipment will
radiate the ingress noise from other sources on the same electrical system.
The cable TV equipment is commonly suspected because it is easily approached
and you are able to put a receiving antenna close to a radiator for the
Often people suspect the power company and other utility equipment because
of the noise radiating from the pole ground.
Send me the file, I'd like to hear it. You can tell him to call me while the
sound is active and I can listen over the phone.
Michael C Martin
6469 Old Solomons Island RD
Tracys Landing, MD 20779
From: email@example.com [mailto:firstname.lastname@example.org] On
Behalf Of Brad Pioveson W9FX
Sent: Wednesday, November 21, 2007 7:21 PM
Subject: [RFI] CATV RFI?
Hey, gang... I'm trying to help a guy that's 80 miles away. He's a relative
newbie to ham radio and has been working for some time with the local power
company to eliminate his persistent, and, apparently, tough (i.e., 20 - 30
dB above S9 on his rx) noise. He sez that the utility guy is now pointing
at the Charter Communications CATV boxes on two specific poles and claiming
that this unit is one of two such units that are responsible for the
residual noise. He's at wit's end.
Our newbie ham has sent me some audio recordings of the noise, and, frankly,
it sounds to me like a bad ballast in a high pressure sodium or merc vapor
lamp fixture. Moreover, the noise is not constant - some days, one pole or
the other will go quiet.
So... I am at a loss. I've never experienced broadband (DC to daylight, he
says) noise from a CATV installation. Leaks on VHF freqs, certainly, but,
never this kind of stuff.
Does anyone have a clue as to what might be happening in a CATV 'large metal
box hanging on a pole' that would cause this kind of RFI? I have audio
files he's sent me that I can share...just not sure if the reflector allows
attachments, so, if you would like to hear it, I'll ship 'em out if you drop
me a note.
Thanks and Happy Thanksgiving, all
73, Brad, W9FX
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