[RFI] Noise Problem

[Richard Battles]

Rodger,
I would think that the RFI is coming from the home, thru the triplex
feeding the home from the power transformer, and the RFI also flows on the
ground system.  I have seen that problems several times,  is the noise just
located around a set of frequencies?  Is it very broadband?  Try using the
rf gain contron with the 20 db attenuation if that control is on the radio,
and see if the rfi is on the ground.  at one time i had rfi coming from a
pole and i was under the impression that is was coming from the cable
system power supplies,  then i discovered that the neighbor had just
replaced the dell pc tower power supply with a no name brand type,  i
replaced the power supply later that week with a dell pc power supply ATX
type and the rfi cleared up.  if the rfi is loud around 3903-3912 mhz and
or 3942 mhz you may a samsung plasma tv.

richard

On Mon, Dec 3, 2012 at 1:05 PM, Roger D Johnson <n1rj at roadrunner.com> wrote:

> 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
> continue.
>
> 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
>
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