[RFI] Noise on 3513.5

Jim Brown jim at audiosystemsgroup.com
Mon Sep 1 14:28:05 EDT 2014

Hi Val,

I've seen reports from others, and it was on my list to listen here. I 
just did, both on my TX antennas and the Beverages, at about 11 am local 
time. I see noise bumps from one or more switching power supplies on the 
P3 spectrum display, but hear no birdies. Then I tuned my trusty TH-F6A 
to 3515 LSB and poked around the only Ethernet gear in my home and the 
CATV cable. Nothing heard. Those were my first guesses, and came up 

My suggestion for chasing this is to do what I did, perhaps 
driving/walking around with a mobile or handheld battery operated rig 
looking for it.  The TH-F6A has very poor sensitivity on HF, so you must 
be right by the source to hear it. A better RX would be one of the 
excellent Tecsun receivers. I own a PL380 (the smallest) and a PL660 
(bigger, 3-6 dB more sensitivity, has a BFO). QST just gave a glowing 
review to the PL880. In addition to their virtues as SW RX, they are 
excellent on the FM broadcast band, and the larger ones (660, 880) are 
quite good on the AM broadcast band.

73, Jim K9YC

On Mon,9/1/2014 10:49 AM, Hugh Valentine wrote:
> Jim,
> I have a varying, warbling, rough tone on 3513.5  CW with K3 running 
> on 12VDC battery,  only rear connection is external antenna...using 
> K9YC 7T 5 Core Choke....All other stuff turned off/unplugged in 
> shack...Computer, Pwr Supplies, Modem, router, Fluorescents, etc.
> I have a VHF "sniffer" that is quiet and does not show any source.
> I have yet to Turn off the Mains...waiting for XYL to go out of Town 
> next week to try that.
> Any thoughts as to the source?
> Val
> N4RJ
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