Hi, I had the same problem on 160m - floating spur was up to S5..7 with antenna disconnected. I tried with 5 different brands serial cables, ferrite chokes, used different laptop power supplies, but that didn't help at all. Only solution was to change computer to newer one. I made K3 "Improving the Immunity of the Rear-Panel RS232 and Audio Connectors to RFmodifications" latter on, but didn't check old computer after.
No idea about other bands. 73 Arunas / LY2IJ /k3 #500 On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote: >This extra noise vanished when I removed the "RS232" cable from the K3. >The cable is actually the one I made up for the K2. There are several problems in the setup. First, the K3 connector shells are not properly bonded to the chassis, so the cable shield is useless. Second, the cable Elecraft sold with the K2-series products used parallel conductors, not twisted pairs. That's a recipe for noise and RFI. I live in a fairly quiet area in the Santa Cruz Mountains, and lots of small electronics produce noise that I can hear, both HF and VHF. Much of that noise is radiated as a common mode signal on the various cables connected to the noise source. I have several suggestions for you. 1) Build the serial cable shown in my RFI application note. http://audiosystemsgroup.com/RFI-Ham.pdf It uses CAT5 cable. When VHF noise is a concern, shielded CAT5 may offer further improvements. 2) Use ferrite chokes on every cable to kill common mode current. A single turn through a #43 core peaks the choking action around 150 MHz. Two-three turns moves the peak down to 6M and provides about three times the choking impedance. If you're concerned about both bands, use multiple cores in series. The equipment at both ends of any cable can be the noise source, so if the cable is longer than about 1/4 wave, use chokes at both ends. I did all of this in my station (and around my XYL's computers) and killed a lot of noise. 3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the chassis. Pin 1 problems couple RFI in both directions -- that is, they let RF into equipment and they put RF onto cables that radiate it. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
