I was one of the guys who, six years ago, found himself suddenly afflicted by a bad-sounding signal from my newly-built K2. It was maddening because every time I buttoned up the rig it would hum. When I pulled the cover off to investigate, the hum went away. After going through that several times, it occurred to me that when I "buttoned it up" I also put it back on its perch atop my small linear power supply! It didn't help that in commercial service we commonly mounted transceivers atop their power supplies for fixed station use to avoid taking up unnecessary desk space. I had never seen a problem with the magnetic field getting into the commercial transceiver. Then again, those were 800 and 900 MHz FM transceivers with receivers that suppressed any amplitude modulation.
My power supply has long since been banished from the operating desk, but since that hum is something that one cannot hear unless one checks the signal with an oscilloscope or monitors it on a suitably well shielded monitor receiver it seemed a good idea to take the precaution of installing the mod. (The signal on a normal receiver often sounds bad simply because very low level modulation inaudible a short distance away may come roaring through, even with the receiver's antenna terminals shorted!) The mod doesn't make the K2 "bullet-proof" in terms of avoiding hum on the signal if the rig is immersed in a magnetic field, but it sure helps! Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
