[RFI] Noise from Switcher on 80/160

Jim Brown jim at audiosystemsgroup.com
Mon Oct 10 13:00:24 EDT 2016

Hi Mike,

See comments below.

On Mon,10/10/2016 9:00 AM, Mike Wetzel wrote:
> I have been experiencing a noise on 160 and 80 for the past couple of months
> that peaks N/NE from my qth. It has peaks every 32.5/65 KHz  across 80
> meters.  I have subdivisions with underground cabling on 2 sides of my
> property (N and NE). Last week, W5LO (who lives in the subdivision to my
> north and also hears the noise) and I took a drive in my car with my K3 and
> we seemed to find the noise peaking in or around a specific house in his
> subdivision. We contacted the owner who did cut the power to the house and
> the noise did not stop.

How far are you driving from your QTH?  When set up for a CQP county 
expedition last weekend, we had electronic noise on 20M. The closest 
possible source had to have been at least a mile away. W8JI has reported 
hearing sources at 2-3 miles.

Also -- when cutting power to a house (or to a specific circuit), a UPS 
may be keeping computers and associated equipment running. AND -- a UPS 
has a DC power supply that keeps the battery charged, probably an SMPS, 
and the power it generates when it loses power will be full of RF 

> A friend of mine, W9KY and I, used his Sony SW receiver and loop antenna to
> try and pin point the noise on Saturday. We heard the noise on his radio
> with a whip antenna at my house and took off walking the subdivision.
> Listening on the loop on 3820 we heard the noise but were not able to pin
> down it's location.  The subdivision does have AT&T U-verse, Comcast and
> many have small DirecTV or DISH satellite dishes/receivers on/in their
> houses. W5LO has DirecTV and we noticed that we heard the noise around his
> splitter coax cables coming from his dish and distributed through his house.
> But even disconnecting power from his unit did not stop the noise. It is as
> if the noise is being radiated from some device (most certainly nearby) and
> is then being picked up by his coaxes.

Yes, possibly coupled as a common mode signal onto his coaxes by another 
piece of equipment that is generating it.

> In W5LO's attic, we could barely
> receive the noise on W9KY's receiver, but when the loop antenna was put next
> to the coax cables, the noise increased significantly again all power off.

Loop antennas couple to other antennas (in this case, the coax). While 
chasing 160M noise at my QTH several years ago with a talkie tuned to 
160M, I copied N7DD loud and clear when I held the base of the talkie 
next to the ground wire on a wooden power pole.

> I am at a loss as to how to proceed and pinpoint this noise source.  Anyone
> with any ideas?

Study the P3 display to learn whether the noise is a "hump of noise" 
that drifts slowly or fast (typical of a SMPS or variable-speed drive 
motor controller) or a distinct carrier that is stable in frequency 
(typical of some sort of digital equipment).  This can yield a clue as 
to what product might be generating the noise.

73, Jim K9YC

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