[RFI] Upstream CATV Transmissions as a Source of RFI?

William Pearson glennpearson at outlook.com
Sun May 24 22:01:24 EDT 2015


I have significant RFI / EMI which essentially makes 10 Meters useless. What
would I see spectrally on a pan adapter if what I see was from  CATV
leakage? I am using a RF Space SDR-IQ with my FT-5000.


I am seeing repetition of a cluster of 4 close spaced signals (no tone) 95
Khz apart. The first three are about 3 Khz wide and spaced about 5 Khz
apart. The fourth one is approximately 5 Khz in width and visually is
heavier coloring on the screen, which take to be strength or intensity.  I
described this RFI as no audible noise. This is on SSB. On AM I hear a low
tone buzz. This cluster with adjacent noise (visible) caused by it will
occupy about 40 to 45 Khz of space. On some days, this RFI is real bad. The
first three blend into the fourth signal such that only the fourth one can
be defined. The bandwidth of the noise can be such that as little as 30 Khz
of space separates each cluster.


For the sake of brevity, I will just say I have gone thru the usual steps in
determining its cause. I have struck out. I know I have a street lamp
directly across the street that is creating havoc on 20 Meters and to a
lesser extent on other bands. There is a second one I suspect on the other
side of my upper neighbor. I am not positive I can exclude the lamps from
this RFI that I just described above but it is nothing like I have read in
the RFI Archives.


This week I had Time Warner Cable to replace their box on the side of our
house. The old one was literally falling apart. We have a history of Channel
18 leakage from several years back. The cause then was a bad port in their
distribution box / amplifier which sits in the corner of my front yard. At
that time all was resolved by moving my drop over to an unused port.


This time the first technician out told me the distribution / amp box was
"hot" with leakage. He tighten a few things and told me he had done all he
could do. He promptly called for the field technician who handles leakage
issues. Several hours later that guy came. He ended up replacing the
multiport device and tightening down all connections. Using his Sniffer,
testing 139 Mhz and 619 Mhz, he attested the leakage had been stopped.


I questioned him about Up Stream Bonded Channel transmissions. He said they
used primarily 19 Mhz, 24 Mhz, and 30 Mhz. The latter two were wide band. He
told me they have had significant issues with suspected RFI on 27 Mhz, with
most cases resolved inside the owners' homes. He did say, the 24 Mhz channel
bandwidth would overlap part or all of our 10 Meter band. I was left to
narrow down some other issues with a sincere promise he would promptly
return if I needed him. I do not doubt this.


Does what I described appear to be related CATV upstream transmissions? For
that matter, anything else familiar?  I would appreciate your input and




Glenn Pearson, WU2G 

More information about the RFI mailing list