Stuart, K5KVH wrote: L. B. Cebik reports favorably on vertical dipoles at Cebik.com. When elevated sufficiently; since they are a complete antenna, not requiring a radial set; they radiate quite well at DX angles.
------------------------------------------------- You are missing the fact that just because an antenna doesn't need a ground (that is, it is NOT a "Marconi" antenna) that the ground doesn't have a dramatic effect on the radiation pattern. Vertical antennas still suffer from far-field ground loss that horizontal antennas do not and do not get the reflection gain that horizontal antennas enjoy. The difference is typically 6 dB lower gain for the vertical under the BEST of conditions over normal earth, providing the horizontal is >1/3 wave high, and up to about 1/2 wave or so. That's as basic to antenna performance as the fact that a 1/2 wave radiator is self-resonant. Now, if you can raise the vertical up a half wavelength or so, it does help, but it never gets as good as a horizontal. That is, if the lower end of a 40-meter vertical is 60 to 100 feet high and the top is 66 feet higher you start seeing some low angle radiation that beats a horizontal at 1/4 to 1/2 wavelength high. But few Hams are in a position to mount a 66 foot vertical with the base 60 to 100 feet up! Even with such an extreme vertical, it's gain is still 4 or 5 dB below a horizontal at 1/3 to 1/2 wave high. You are absolutely right: Cebik has some excellent material on the WEB and he deals with this very issue at: http://www.cebik.com/fdim/fdim4.html Note the difference in the lower angle radiation from a ground-mounted vertical with various ground losses from a "perfect" ground to poor. That "perfect" ground is why verticals work so very well at sea or at the sea shore. Salt water isn't perfect, but it's a whole lot better than dirt, even wet, marshy dirt. The only issue I take with that data is that it shows a horizontal as having the same gain. His scale is wrong, both according to his other pages concerning horizontal antennas and to other references such as Moxon or modeling software such as EZNEC. All of those source say the dipole will be roughly 6 to 7 dB better if it's upwards of 1/2 wave above the earth. Verticals work. They work very well. It helps tremendously to have a full-size (i.e. half wave) vertical since there are no losses that often appear in a Marconi (1/4) wave vertical, although with care a 1/4 wave can be very efficient as well. The great work done by Gary Servick, W2FMI, showing that a 6-foot tall top-loaded 40 meter vertical can be very effective is a good example. His work was published in QST (one article in the April 1978 issue) and in other ARRL publicatins such as "Vertical Antenna Classics" published by the ARRL. No matter what you do, the polarization of a vertical is still vertical, and they don't get the reflection gain that a horizontal does from the earth. Of course, as Cebik points out, you can often phase several verticals to produce a very effective directional antenna in a lot less space than you'd need for a similar horizontal antenna on the lower bands. Ron AC7AC _______________________________________________ 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
