[Elecraft] RFI PC Speaker Hum

[David Ferrington, M0XDF]

I have Harman Kardon speakers & sub on my Mac via USB and another pair, different model, same manuf., traditional audio from headphone out, generally no poblem. Never had any RFI on the Mac ones, occasionaly get it on the others - but I have a lot of RF in the shack (something I need to fix).
73 de M0XDF, K3 #174 
-- 
Math Anxiety: an intense lifelong fear of two trains approaching each other at speeds of 60 and 80 MPH. -Rick Bayan

On 3 Jun 2010, at 12:25, Julian, G4ILO wrote:

> 
> All computer speakers are amplified. Many of them have very poor immunity to
> RF. I have sometimes reduced RFI to acceptable levels by winding a couple of
> turns of the cables through snap-on suppression toroids. Winding several
> turns through a large ring toroid would be more effective as the snap-on
> suppressors are really only designed to suppress VHF.
> 
> Some computer speakers have such poor RFI immunity that they are probably
> beyond fixing. One pair I bought made by Logitech hummed even when placed
> near a cordless phone base unit that probably has an output power of a few
> milliwatts. The first time I pressed the PTT of my transceiver the resulting
> noise nearly gave me a heart attack. I gave them to a charity shop. There is
> a firm (I think it may be the one that makes RigBlaster interfaces) that
> advertises RFI-proof computer speakers, but I seem to recall the last time
> they were mentioned on this reflector they were out of stock.