On Wed, 24 Feb 2010 14:18:50 -0800 (PST), callen1155 wrote: >I'm planning on purchasing a K3/100 but am concerned about my second floor >shack and RF problems.
The most important thing to understand is that a connection to EARTH has NOTHING to do with RFI, or RF feedback, or any of the problems you are describing. The word "ground" in this context really means "signal common" and "shielding." I ran 1.5kW from a second floor shack in my wood frame house in Chicago. I used mostly dipole antennas that were no more than 40 ft off the ground, so only about 20 ft above my operating desk. There was direct radiation of RF from those antennas into wiring in my shack and in my home, but the only problems came from improper connection of cable shields in equipment. I also ran 1.5kW on 160M and 80 into a long wire antenna that ended in my shack. As a counterpoise for that antenna, I used a large wrought iron fence that ran around the front of my city lot, roughly 150 linear feet, 6 ft high, plus some wire radials. That antenna had a very strong current peak at the transmitter, so there was a very strong magnetic field sounding it. The only problem I had with that antenna was with the stock control cable for my K2/100, which was parallel wires in a foil shield. I replaced that cable with twisted pairs, with one side of each pair serving as signal return and connected to the chassis of the computer and the chassis of the K2. That solved that problem. A radio does not need ANY connection to the EARTH. If you doubt that, think about how radios in aircraft work! Didja ever see a 747 taking off trailing a ground wire? What I strongly recommend for your new QTH is resonant antennas fed with coax. Keep them as far away from your home electronics and from your shack. Use good coaxial ferrite chokes on all the feedlines. Study http://audiosystemsgroup.com/RFI-Ham.pdf 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
