Simon, The K3 has RF decoupling, but it also has a pin 1 problem. The "pin 1 problem" is the design error that connects a cable shield to a circuit board signal common rather than to the chassis. RF current then wanders around that common, and the IZ drops on common inject it into active circuitry at the whim of the PC board layout artist.
Hams are surprisingly ignorant about the immunity of interconnect cables. The K2 shipped with a cable that was shielded but consisted of parallel wires. I had BAD RFI with it at only 12 watts out! We're also lazy -- preferring to run down to Radio Shack and buy a pre-made cable than to pull out a soldering iron and build a proper one. Since I work in pro audio and am an EMC specialist, I knew that twisted pair cable provides EXCELLENT immunity to noise and RF pickup, FAR more than straight wires inside a shield. I solved the problem by replacing the stock control cable with one made from ordinary unshielded CAT5 cable. I wired the cable using one pair for each signaling circuit used by the K2 and my computer, with the return conductor of each pair used as a signal return. That is, one pair for pin 2 and return, one pair for pin 3 and return, one pair for pin 4 (CW) and return, the fourth pair for pin 7 (PTT) and return. The second part of the solution was solving "the pin 1 problem." I did that by making the "return" connection on each end to the DB9 shell. Using that simple UNSHIELDED CAT5 cable I was able to run 1 kW into a long wire antenna on 160M and 80M that ended in the shack and ran only about 1 meter from that K2 control cable! 73, Jim Brown K9YC --Original Message Text--- From: Simon (HB9DRV) Date: Thu, 25 Dec 2008 20:07:44 +0100 A FT-2000 user with a big hairy amp and a CAT cable connected got so much RF into the CAT cable that he blew the UART in the FT-2000 and the serial port on the PC. This happened when the antenna was rotated to point at the shack. I wonder whether the CAT port on the radio has RF decoupling? Simon Brown, HB9DRV www.ham-radio-deluxe.com ----- Original Message ----- From: tom kenville Last evening I had an annoying problem with K3. It would stop transmitting any signal, even though the red xmit light was lit.
_______________________________________________ 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
