Rick, I didn't mean to imply anything about the efficiency of the R5/R7; they are quite short with lots of compromises, and there are certainly ways a vertical antenna in general may, in a given installation, have specific limitations. Certainly I rarely use mine as I get much better results with my horizontal beam (Sommer XP708). My comments regarding the R5 were meant to be only about issues with matching and rf in the shack etc.
I agree that reality isn't always in agreement with the theories at hand. That is why I plan to compare the end-fed with a center-fed before I commit to it for personal use. In a previous thread I have outlined my planned comparison, "side by side", trying my darnedest to notice any performance loss resulting from the endfeed. We shall see about that. I won't take up space here to repeat all the discussion about that testing. What I have tried to say in this thread, is that I am rather confident that I can "tame" the end-fed in the sense that it won't cause problems with rf in the shack, and regarding performance I will assume there is no problem until my comparison shows that there is. The original poster had a problem with coaxial protection devices, and if I understood his configuration correctly, such problems could be anticipated in that configuration. I pointed to end-feed with tunerless low swr as a potential approach to make those protection devices work as intended, with a radiator that is the same length wire as what he had. Your antenna farm is a separate subject, as is mine, and in this thread I will just comment briefly on those subjects. I got interested in SO2R, but don't have space for two towers/beams. You may not be thinking about SO2R, but if you are, and if you too can't put up a second tower/beam, then you might want to think twice about using SteppIR. With a beam that can work multiple bands without retuning, I use a multiplexer that allows two transmitters to use the same beam as if I had two separate ones. (Minus the capability to point them in different directions!). If an end-fed wire antenna works well without tuner on multiple bands, it can also be used with a multiplexer to perform instantly on another band, without retuning. Not so with a simple center-fed dipole (but a fan or trapped dipole would be ok). My other comment is about your verticals fed against a pipe in the ground. When I was using inverted L's for 160 and 80, I first tried them against a single, 4" wide copper s trap going part way around the house and tied to a few ground rods here and there. Then I tried it against two zigging wires used as elevated radials. This worked much much better. Like others have said so often and so well: If you are going to bury radials, it will take many of them. 73, Erik K7TV -----Original Message----- From: Rick WA6NHC [mailto:wa6...@gmail.com] Sent: Saturday, February 24, 2018 10:30 PM To: Erik Basilier <ebasil...@cox.net> Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] KPA500 faulting on high VSWR on power rise I have an R7 (end fed vertical 40-10M). It and a 80M dipole are my current antennas, until I plant a tower later this year (55' US Tower, motor drive, tilt over). I have to admit that I'm not a fan of vertical antennas. Since I moved here last year and haven't gotten the tower up yet, the R7 is 'adequate' for a temporary antenna, but dipoles are more effective. It also provides decent diversity reception with a horizontal dipole. (The new antenna, when it gets up, is a SteppIR DB-42 at 60', resonant 80-6M then I'll add in a Beverage for RX only since I have the space now or a K9AY. I have a 160M inverted L up too (bend at about 90'), using the underground water pipe as the counterpoise, buried down 4-5', 1:1 CMC at the base, it was quick and simple. I'm adding a tuning network to that so that will be a 80/160M resonant vertical, giving me another option on 80M.) The beautiful part is that with only 2 resonant antennas, I can cover 160-6M once I'm done, perfectly matching the new KPA1500. Simple ROCKS! The R7 (like the R5, 8, 9) has a matching network (torroids mostly) in the black box and trap and capacitive elements on the main element and short radials at the base to get it to load, but that doesn't meant that it's efficient; it means it presents a load that is acceptable (so does a dummy load). The EDZ at my last QTH beat the R7 in almost all scenarios on any band, unless the other station was off the ends of the dipole, then it was even money; which left the R7 being used for diversity. So it works, but I wouldn't rate it highly unless one is limited by space, HOA or similar. It reacts badly when near (w/in 10' of) any metal and the base must be at least 10' AGL. Adding more choking is very wise. I would expect similar results from a non-commercial antenna, unless used only on one band (and it's still a challenge to tame). Dipoles are much simpler, even when used for multiband operations. Cut the antenna to the desired (available) length, add the feedline, measure, adjust for local conditions (add/cut feedline for open wire or antenna for single band) then see how it plays. Add common mode choke transformation (1:1 vs 4:1) to keep the currents outside the shack, feed with no more than 10' of coax to the final; have fun. Reality beats textbook every time since the textbook doesn't know about the septic field, tree proximity or the dog kennel fence, let alone actual height above ground which isn't always the top layer of dirt. Go play, have fun, it's part of the long tradition of ham radio. 73, Rick NHC On 2/24/2018 3:45 PM, Erik Basilier wrote: > A lot of users seem pleased with end-fed wire antennas of recent commercial > models. Such antennas should not behave much differently compared to end-fed > verticals such as the R5 that I have had for many years and which creates no > problems even at high power. Like that antenna, the wire models now becoming > popular use a high ratio wide-band impedance transformer. The R5 also > includes tiny radials and a common mode choke at the feedpoint. The R5 > behaves well even at high power with its feedline length of maybe 50ft, and > there is not enough RF in the shack to affect the operation of radios or > other equipment. However, for good measure I added a second common mode choke > in the form of several ferrite snap-on's about 10 ft from the feedpoint and > then found a noticeable reduction in shack RF (measured in the shack using an > MFJ RF current sensor). I believe there are lots of satisfied users of the > Cushcraft endfed verticals. As to the wire end-fed's I am constructing an > imitation of a popular commercial version, and will find out for myself if there are any difficulties. I will add a common mode choke placed either at the feed point (like the R5) and a separate counterpoise, or I might try placing the choke a distance away from the feedpoint to let a portion of the feedline act as counterpoise. Again, a second common mode choke further down the feedline will likely be added. Based on the positive reports by so many users of the commercial versions, who apparently don't add any common-mode chokes, I am fairly confident of success. > > 73, > Erik K7TV > > ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
