Right. That makes sense. Though the worst case would be a 2:1 SWR if both are resonant, because the feed point impedance would be 1/2 what is expected. Not the end of the world.
A 40m dipole isn’t quite resonant on 15m anyway, so having both might make for more broadband 15m behavior with fewer broadside nulls. The ARRL Handbook includes a design with capacitance stubs to fix the resonance on 15m. My setup is an 80/40/20 fan dipole with a neat trick. The 80m dipole is center loaded, and the center section is cut to resonate on 20m. In parallel with that is a full-sized 40m dipole. The loaded 80m element is just a few feet longer than the 40m element. That is the 3B2080LFAN from Hy Power Antennas. Good construction at a good price and a clever idea. http://www.hypowerantenna.com/products/fan-dipole Walter Underwood [email protected] http://observer.wunderwood.org/ On Sep 14, 2014, at 12:16 AM, Bill Frantz <[email protected]> wrote: > Fan dipoles depend on the relatively high impedance on the fan pieces that > are for other bands to send most of the energy into the tuned fan. If you are > using fans for 40 and 15, the energy will be split between them on 15M which > isn't what you want. > > BTW - My combination of a 160M dipole commonly fed with an 80M inverted V at > 90 degrees to the 160M dipole works quite well on 15 meters. The cocoaNEC > model shows good performance with 4 major lobes arranged more or less in the > direction of the 160M wire. > > 73 Bill AE6JV > > On 9/13/14 at 11:14 PM, [email protected] (Walter Underwood) wrote: > >> Eh? A 40m dipole is pretty close to resonance on 15m already, so how can you >> avoid that. In fact, all dipoles are resonant at odd multiples of half >> waves, so this is impossible to avoid. >> >> Could you clarify the issue here? >> >> wunder >> K6WRU >> CM87wj >> http://observer.wunderwood.org/ >> >> On Sep 13, 2014, at 10:31 PM, Don Wilhelm <[email protected]> wrote: >> >>> I failed to mention another point with regard to fan dipoles. Do not mix >>> 3rd harmonic radiators on >> the same coax. In other words, stay away from combinations of 40 meters and >> 15 meters, and also 40 meters and 30 meters. They may work, but tuning >> problems are 'iffy'. >>> >>> 73, >>> Don W3FPR >>> > ----------------------------------------------------------------------- > Bill Frantz | Since the IBM Selectric, keyboards have gotten > 408-356-8506 | steadily worse. Now we have touchscreen keyboards. > www.pwpconsult.com | Can we make something even worse? > > ______________________________________________________________ > 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]
