Good stuff as always Ron, thanks. The multiple wires on the fiberglass is a VERY interesting idea.
Plus if I add sections, 43'ish is 5/8 on 20m, the main ban I operate on. I am mainly interested in 40' and up. I'll get 80 and 160 with other wires. Thanks for taking the time to reply Ron. I seldom walk away from one of your enjoyable posts without learning something. 73 Dave Wilburn NM4M Ron D'Eau Claire wrote: > If you are talking about multi-band operation, you can expect the SWR to > range up to above 60:1 on some bands, particularly where the radiator is > near 1/2 wavelength. That's why ATU's designed for operation at the antenna > are used for such applications. And, yes, they tend to be expensive. > > The Stepper antenna adjusts its length to 1/4 wave on the band in use, > AFAIK. That way it presents a decent match to coax on any band in its range. > > However, matching to a longer antenna up to 5/8 wave provides substantial > low-angle gain over a 1/4 wave radiator. That's easily done with a matching > network at the base. > > One way to accomplish that at a lower price than a commercial ATU at the > antenna is to put in a matching network for each band, relay switched, at > the base. On some bands only an inductor will be needed, with taps for each > band selected by relays if you are adverse to going out to the antenna. On > others capacitors may be involved (such as when the antenna is near 1/2 wave > long and presents a very high impedance at the base). IN that case you might > have a separate network that is switched in. > > It's not as "hammer simple" as buying an ATU and plugging it in, but it can > be even more efficient and at a lot lower cost. For many of us, that's what > makes Ham radio fun: doing for $1 what anyone with a fat wallet can do for > $100. > > You can probably get away with one matching network setup per band, at least > on 40 and up, and keep as low an SWR to the actual rig as you want using the > rig's built in ATU. (That's what it is really for ;-) Just be sure the SWR > on the coax isn't so high you have unacceptable losses. > > With an insulated pole like you have, another way to economically arrange a > vertical covering several bands is to tape several radiators to it, > insulated from each other, each 1/4 wave long for the band of interest. You > can feed them in parallel with one run of coax, especially when dealing with > harmonically-related bands (e.g. 40/20/10 meters) but it can be made to work > on other combinations with a little pruning so that the SWR is low enough to > avoid excessive coax losses. Then you let your rig's ATU do the final > tweaking to keep your finals happy. > > You might do a little research on radials. The relationship of the number of > radials to antenna efficiency is not linear. The more radials you have, the > less adding more improves the efficiency. Also, the higher the feed point > impedance, the less important near-field ground losses become. For example, > a half wave radiator with a feed point impedance typically several thousand > ohms is very efficient with no ground connection at all. OTOH a 1/8 or 1/16 > wave radiator with a feedpoint impedance of less than an ohm requires the > best possible ground for any reasonable efficiency. > > > Ron AC7AC > > > -----Original Message----- > Recent discussion regarding verticals, internal antenna tuners and > remote antenna tuners was very interesting. Based on that discussion, > it seemed the "optimized" solution was a vertical, with good radials, > and a remote tuner at the base (generalization). > > In the near term I want to try out (experiment with) a 33' vertical. > At Frostfest this year I picked up 32' or so of fiberglass mast. I am > going to tape a wire to this that is 34' long, twist the mast to wrap > the slack up, much like a widely spaced helical. > > When setup at home, it would (eventually) have a good ground field > (would start out with 16 radials and work my way up to 60'ish). The > coax run when used at the house would be less than 40'. > > When setup for portable operation (connected to mount I have for my > trailer hitch, to use when parked) it would have 4 radials of a length > not yet determined and the coax run would be less than 20'. > > In both cases I would be using the tuner for the K2 (portable) or K3 > (at home). > > In the long term, I am thinking about the SteppIR vertical (haven't > decided which one). Same deal with the radials. It would inherit > what I had down, or start at 16 and work up. > http://www.steppir.com/files/vertical%20brochure.pdf > > Current plans are for ground mounting. I understand that as radials > go, more is better. The radials would be black insulated wire on, or > within 1" of the surface of the ground. They would not be cut to 33' > or less if the space was not available. > > I am curious on the experience of the group with a similar vertical, > tuner at the rig, and short coax run. > > I am also curious of the experience of the group with the SteppIR > verticals. There is similar up front cost as the vertical / remote > tuner solution (assuming a new weather proof tuner). > > Thanks for the always enlightening discussions. 73 > > Dave Wilburn > NM4M > > ______________________________________________________________ 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
