The Windom is not a cure all antenna, and indeed has a number of potential problems. Its original version was a one band antenna, and modern uses of similar antennas are like stuffing a model ship in a bottle--doing something other than the physics show is the simplest antenna.
As an off center fed antenna, it is unbalanced. This may increase RF in the shack problems. Especially as you move off the one sweet spot where it is naturally resonant. If you feed it with other than single wire, you can limit the feedline radiation but at the expense and weight of a balun or RF blocking ferrite beads on coax. Depending on the length of the feeder and how it is brought away from the antenna, you are not likely to maintain an RF free feeder, because the capacitance of the outer shield of the feeder is different to one side of the feed point than to the other (which are differing length legs of the dipole.) The "Windom" type (or Off Center Fed as the general class of antennas is called, will have an offset modified dipole pattern; it certainly will have something other than an omni pattern due to its imbalance and lack of symmetry. Like any dipole class antenna, it will have more of an bubble of radiation if placed too low. This will cut its directivity, but then you will have to rely on field strength measurements to see what it really is doing. A dipole for say 20m or up will certainly perform as the models show if you have a clear near field area around it, and it is 50 feet high, even the 40m dipole will perform pretty well in that case. What the dipole offers is a chance to bring the feeder off at a right angle, and maintain a true balanced antenna with symmetric pattern, if no nearby conductors affect the field. What I am saying is there is no magic antenna, you really need to match the antenna to its surroundings, and that may mean some compromises. But, you should not intentionally complicate your antenna installation, IMHO, by using antennas that aggravate RF in the shack possibilities. Nor should you use an unbalanced antenna intended as a single band antenna on other bands without expecting some problems or the need to use a tuner for each frequency excursion. Even the G5RV which can work well for some at low elevations with certain precautions, was only intended to enhance the 20 m band use by providing gain there. I have used a number of versions of the G5RV; and they universally present a poor radiation angle on 15m compared to other bands. They will work well on 40m, but need a tuner in most other bands, again depending on local installation conditions. A good all around installation is use of the 88 foot doublet, (or 44) for reaching more bands with a tuner and reasonable results. But, usually, a pair of antennas is good to have. A dipole/ doublet for low bands, and a vertical for bands 20m and up. You get low angle of take off and omni coverage from the vertical; and you get usual doublet performance dependent on height from it. To overcome the usual complaints and problems of verticals, use a vertical dipole. Both an elevated feedpoint and elevated radials on quarter wave verticals seem to enhance performance. Even loaded center fed dipoles are quite good performers, such as the Force 12 Sigma line. However, with a little pre planning, one can homebrew just as good a vertical doublet. One of the ideas I found for test for an experimental vertical doublet is one of the larger sizes of PVC pipe splices for a center insulator. These devices have a compression fitting that should tighten around tubing used for elements. They would also work as bottom insulators, or you could use PVC rings under U bolts as done in the Titan vertical. Of course, non conductive guy lines would be used, but the overall antenna design is simple and easy to put up. One idea is to center feed with parallel wire line, and by use of a tuner, cover multiple bands above the half wave resonance of the vertical dipole. This would remove the need for loading coils and a switching network. -Stuart K5KVH _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
