Hello Elecraft'ers I have been trying to figure out a decent antenna that can be used indoors with my K2(until I can get permission to install an antenna on the roof) to use on the 3rd story of a 5 story 1828 apartment house in downtown St Petersburg Russia. Being such an old brick building the walls are 1 meter thick at their thinnest. The leakage from cable TV, DSL and electric trams cause a high noise level and the poor antenna options make for weak signals. I went to the woods this weekend and tried a new 40m dipole and heard a lot more with the low noise level out there. When I returned to the city I was more determined than ever to get something up that was more effective than the 20m inside dipole I have been using.
I found a small plumbing shop open late and bought 4 meters of 1/2in copper tubing and made a loop this evening. I had no high voltage capacitors so cut various lengths of RG-58A to use as coax caps and kluged a Faraday shielded loop coupling system to drive the main loop. None of it is permanent yet but after only working on it for 30 minutes total, I have been amazed how well it works with the low power version K2. Comparing the loop sitting vertical in my living room the noise level is 10db lower than the indoor dipole and signals are steadier and much easier to copy. The difference in fading depth is dramatically improved. The bandwidth for 2:1 SWR on 20 is 80khz without retuning the center of which is 1:1. I only set it up for 20 and 40 but using fixed lengths of coax as the tuning capacitor but during my experiment I found the loop worked on 80m also but with higher SWR. Obviously I need a real variable cap which the electronics parts stores here don't have(all the experimenters it seems were born in the digital age). So back to the plumbing shop tomorrow for parts to make some piston caps. I'll build the caps with 5kv or higher so if I get the 100watt K3 I'll be ready. A big plus is being able to match the antenna directly bypassing the KAT2 for higher efficiency. My built-in K2 tuner is more efficient than my MFJ tuner even though the MFJ has some usefulness for use with balanced lines and built-in dummy load. Anyone else build small loops for use with their QRP rigs for a while? The only down side I've seen is the need for more complex remote tuning and narrow range before needing to retune. What has been your experience? What am I missing, since the magnetic loop seems to solve so many problems for antenna restricted stations why are they not talked about more often? Stan KM6XZ St Petersburg Russia ______________________________________________________________ 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
