Re: ferrite vs sensitivity
Pollock,Raphael E <rpollock@...>
Dear George: Your 17 swallows analogy got me to really laughing! In any event, I will await your practical applications in that the vast majority of our fellow hobbyists, myself included, lack much in-depth knowledge about the underlying electronics, let alone the theoretical modeling that you are so generously providing to us. It will be a real service to the hobby to be able to come forth with an optimized and practical application, including step-by-step instructions as well as supply sources. It may very well be that a 7.5” ferrite bar, such as what is being used for so many of the boosted Tecsun ULRs, is the best option, end of discussion. I continue to be very pleased with the 19” ferrite bar booster that I built, “designed” by reading through sources from the various Yahoo clubs, the web, Gerry’s Q-stick + which is my original inspiration, etc. All that is well and good, but is it the best that can be done??? If I am to interpret the graphs below correctly then a 19”L x 1”D 125 mu ferrite bar wrapped with a primary coil of 38 turns should yield a SNR of about +6dB and a 27” L x 1” D would be about +8dB. As a practical matter both of these antennas generate just about the same amount of apparent gain when inductively coupled to any of several radios that I own that have S-meters—slightly more gain with the 27”er but not enough to have ever made a difference in being able to receive a weak signal, plus the nulls are sharper with the 19”er.
I am really enjoying your insights, and look forward to more. BTW, basic demographic info? I’m about to turn 60, have been playing w/ radios since second grade, am a surgeon and work/live in the middle of Houston, TX. If I had been better at calculus I might have gone into EE; instead, I stand on the sidelines and play around with ferrite bars and wires and PVC piping while being taught by smarter folks like yourself!
ultralightdx@... [mailto:ultralightdx@...] On Behalf
Of george magiros
I'm still on my quest to simulate ferrite loop
antennas, this time for their signal to noise ratios. I hope I'm not
proving that 17 swallows are as strong as a horse with all my graphs.
Experimentation and actual DXing comes next I promise.