Jim, Can you toss a capacitive hat on the top of the shorter vertical and see what difference that makes? I've not figured out how to use the modeling software yet!
- Brendon KK6AYI On Thu, Mar 24, 2016 at 11:14 AM, Jim Brown <[email protected]> wrote: > On Wed,3/23/2016 7:12 PM, Wayne Burdick wrote: > >> I've been using an MFJ-1820T telescoping 20-meter whip for a few months. >> Considering its length (48"), results have been excellent. I typically use >> it with the KX3 on a picnic table at 15 W (with an external battery), or >> hand-held at 3 to 5 W (internal battery). >> > > As Tom Schiller, N6BT, famously noted, EVERYTHING WORKS, sort of. He > demonstrated this by working all continents loading a lightbulb that he fed > with coax. Tom is the designer of the excellent Force 12 antennas. > > I just did a quick NEC model of a 4 ft vertical with loading coil and a > single quarter-wave radial laying on the ground, and compared it with a > quarter-wave vertical (16.7 ft) with the same single radial. The model is > for poor soil, which is typical of most mountainous QTHs. The full-size > quarter-wave will be 7.4 dB louder than the shortened one. That's > equivalent to reducing a 15W signal to 3W. The difference is slightly > greater over better than average ground. The reduced efficiency is due to > the greatly reduced radiation resistance of the shortened antenna. > > Bottom line -- yes, shortened antennas work, sort of, but full-size > antennas work BETTER. If you can afford the weight of a means to support > the longer antenna (typically a telescoping fiberglass pole), it's well > worth it! And if a shorter antenna MUST be used, LONGER antenna, LESS coil > is better. > > 73, Jim 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 > Message delivered to [email protected] > ______________________________________________________________ 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 Message delivered to [email protected]
