Topband: Need help identifying RFI source

Rob Stampfli rob at
Mon Jan 24 11:28:47 PST 2011

On Mon, Jan 24, 2011 at 08:20:35AM -0600, K4RO Kirk Pickering wrote:
> I have been plagued recently by a noise source which is
> wiping out signals on the 160m and 80m bands. It is 20dB
> louder on my SW Beverage than any other direction.
> The noise is intermittent, and comes on for roughly 10-15 
> minute intervals, and when it goes off, it is completely 
> quiet for another roughly 10 minutes. The amplitude peaks
> are at approximately 20-30 kHz intervals, an seem to vary 
> somewhat with frequency. I can hear the noise from about
> 1600 to 4200 khz. It's really hurting my 80 and 160 meter
> reception. Here is what the noise sounded like this morning:
> Before I start hunting, I wonder if anyone has heard this
> type of noise before, and might be able to identify it? 
> Thanks for any suggestions.

>From your description, I strongly suspect it is a high efficiency
furnace -- most likely caused by either the inducer motor or a DC
blower motor.  I've heard of numerous complaints about this recently,
some even on this list, and have a friend who is being plagued by
his own new furnace, which is essentially wiping out his HF

Do you have a neighbor who perchance has installed a new furnace
recently, perhaps just before the new year in order to take advantage
of the expiring tax credit?

Rob / KD8WK

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