[RFI] Cable TV Interference

Tom Rauch w8ji at contesting.com
Thu Sep 21 19:58:25 EDT 2006

> An update with my problems with cable TV interference.
> 12:00 PM  Receiving cable channel 38 at 4.821 MHz
> 4:20 PM   Receiving cable channel 11 at 4,831 MHz


TV sets use 4.5MHz IF and some subcarrier frequencies in 
that range and higher as an FM (audio) IF. I can hear the 
sound carrier from what I suspect is the composite video 
cable connects between my TV set and DVD/VCR if I pull the 
plug back and get a bad ground on the shield. The color 
burst is around 3.58, and the color IF extends up to 4.08.

You might check and see if when you are having the FM sound 
you are also hearing a strong buzzing carrier around 3.58MHz

I'm only guessing but I suspect you have a similar problem 
with a neighbor, not with the CATV company. I would be 
especially suspicous of a TV set or VCR system since you 
report the channel changes and sometimes disappears.

73 Tom 

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