Hello Mike. My EFHW vertical is resonant only at 20 meters. The *antenna* SWR is lousy everywhere else according to my MJF259 which stops reporting at 25:1. -- just as bad as my non-resonant-by-design 44' Cebik doublet with which I've worked the world, at 5 watts and below. The internal tuners in my KX1, K1, and K2 all tune the antenna between 1:1 and 1:4. I've used this vertical with good results on 40 meters and *great* results on 30, 20, 17,12, and 10.
My use of *great* is within the following context: I have little test equipment and my background in electronics is truly 'amateur'; I'm still learning after 51 years and I never seem to be able to learn enough, fast enough ;). Hence the use of the word 'empirical' in the Youtube description to underscore the casual nature of this rather interesting comparison between W1ZMB's OCF up in the clear and my new antenna toy sitting on his deck. All I can say is that the darn thing produces great DX QSOs for me on my 5 watts or less and affords me a second antenna option in my antenna restrictive community. Sometimes, a signal is louder on my doublet than the vertical or vice versa: a quick flip of a switch and I can try the other antenna. It's nice to have that option. The 9:1 UNUN I used (purchased from the Emergency Radio Club of Honolulu) was my choice over a parallel tuned circuit because my goal was to end up with the easiest and fastest antenna to put up and take down and use. I don't have to stand next to the antenna and tune a capacitor this way. I realize my choice might not be technically optimum but once again, it reflects the goal I set for myself. I'm using 20 gauge teflon coated wire because the 33' MFJ pole tapers to an extremely thin final section - closer to an ultralight fishing pole. Anything larger than 20 gauge starts to bend the pole's tip over. In my own experience - and I once again admit my technical weakness in the subject area - I have experienced no difficulty with extremely thin wire at the QRP levels I operate at. In order to put less strain on the wire during frequent set up/takedown I chose to wind it around homemade clips as shown in the video which give me about an 18" diameter. The video shows how quickly it can be done with no tangle. The 22 gauge toroid wire is what the Honolulu folks who designed the UNUN used. It seems to be a frequently occuring wire size in other EFHW papers and construction articles I've read. Again, I'm sorry that I don't have the technical background to comment further. stan WB2LQF On Sat, Nov 12, 2011 at 1:14 PM, Mike Morrow wrote: >> http://www.youtube.com/watch?v=uWkpQ785Pjo > > That is an interesting demonstration, Stan. I have a couple of > questions. > > It is stated that the VSWR was no greater than 1.4:1 on 40 through 10 > meters. > But it appears to me that these figures report only the lowest VSWR > that the > K2's ***ATU*** could produce, NOT the actual VSWR that existed on the > antenna > side of the ATU. That seems at best be a measure of K2 ATU > performance. It > says nothing substantive about the characteristics of the attached > antenna. :-) > If that is correct, do you have any figures for the VSWR that the > antenna > with transmission line actually presents to the tuner? The impedance > plots > from a good antenna analyzer would be most interesting. > > Why use thin 20 awg wire along the mast as the radiator? In my 35 > years of experimenting with portable wire antennas, I found nothing > but trouble when > using such extremely small diameter wire. Instead, for more than 15 > years I've > used 14 awg Flexweave-tm which consists of 168 very fine strands of > copper. > It is a dream to use, and it never suffers fatigue failure. I've > never had a > portable wire antenna to fail since I started using Flexweave. It's > available > bare or insulated, and either will tolerate frequent spooling and > un-spooling > for the life of the antenna. > > I also question the use of 22 awg wire in the toroidal transformer. > Such small > conductors represent just as much RF loss at QRP as at 200 watts. > Much larger > conductors would be appropriate there as well. > > There is no advantage to small conductors in any HF antenna design, > especially > for QRP use. I also cringe at the RG-174 coax crowd. :-) > > 73, > Mike / KK5F ______________________________________________________________ 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
