[RFI] Noise Problem

Roger D Johnson n1rj at roadrunner.com
Mon Dec 3 14:05:30 EST 2012

The problem continues. I found out that the cable amps are
powered by 60 VAC sent down the cable. The cable company
sent a tech out at 1 AM to disconnect power to that leg
of the system. I was very disappointed to see the interference

I bit the bullet and installed the K3, laptop with NaP3, the
LP-Pan box and a Sony AN-1 active antenna in the wife's car.
I went back to the area to see if I could pin down the location
on the noise. The spectrum analyzer feature of the NaP3 has
much better amplitude resolution than the RS DX-390 with a
LCD bar display that I used earlier. I drove up and down the
road several time to ensure I had the correct peak. I then
drove into several driveways to see if the noise might be
coming from a house. In all instances, the signal strength
decrease as I went away from the cable/power line. The noise
seemed to peak at a pole with a transformer, a cable drop
feeding the same home and some sort of cable thingy. It's
a rectangular black box about 12-18 inches long hanging from
the cable. Just for the heck of it, I took out my HT and a
3el Yagi for 2m that I use for powerline noise finding. I
tuned the HT to 145.25 (the video carrier for cable channel
18). I immediately picked up a loud buzzing when the antenna
was pointed at the cable hardware on the pole. I tried 149.75
(the aural carrier)and also heard loud demodulated audio.

I had postulated earlier to the cable company that I thought
the noise source might be switching power supply noise leaking
from the cable. It seem to much of a coincidence to have the
noise peak at the same pole with a lot of signal leakage.

Just wondering if anyone has had any problem with cable TV
disribution amps causing noise problems.

73, Roger

Remember the Liberty (AGTR-5)

More information about the RFI mailing list