I agree with Dale. (We're in the same line of work.) I've heard EMI from
DC brushless fans before. Usually, not enough to be a problem, but quite
similar to what you've noted. Probably, some fans have poorly laid out
boards ("It's only [audio, DC, control, 100 Hz etc]. we don't need RFI
prevention!) and under certain conditions can oscillate, generating pulses
at a rate depending on motor speed.
Cortland
KA5S
> [Original Message]
> From: John Rader <k5xtx@hotmail.com>
> To: <rfi@contesting.com>
> Date: 10/14/2004 6:49:36 PM
> Subject: [RFI] Astron fan circuit noise
>
> My Astron SS-30M makes noise on 80m each time the fan starts. The noise
> starts out low in pitch and increases for about 10 seconds then stops.
The
> fan continues to run for about 30 more seconds. It is not related to fan
> speed or duration, only starting.
>
> Any Ideas on how to eliminate this noise?
> John K5XTX
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