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I want to make a longwire/Beverage receive antenna that will work on a wide range of bands (80-10m or wider). I've got a place where I can put a wire of at least 50m/150'. The only problem is — the shack is sitting right in the middle.
So I have three options basically:

  • Use only half of the distance and make a 25m antenna (waste of space and opportunity)
  • Run a 25m/75' coax from the end of the longwire to the shack (quite expensive... I might be better off buying a sophisticated antenna instead! Ruins the whole idea of "cheap field-expedient piece of wire")
  • Some kind of center-fed longwire?..
Alexander
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  • A center fed longwire can easily be turned into a dipole. May need some matching to work over a wide band of frequencies. – Phil Freedenberg Jul 01 '21 at 23:17
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    Isn’t a non-resonant (or non-multiple thereof in length) balanced wire antenna called a doublet? Feed it with balanced line, and use a tuner. – hotpaw2 Jul 02 '21 at 04:16
  • Of course @hotpaw2! I've just read its description in the ARRL Antenna Compendium and that's exactly what I need :) If you write that as an Answer, I'll accept it, thanks! :) – Alexander Jul 02 '21 at 11:14
  • Yes @PhilFreedenberg, my first idea was a dipole... and I immediately thought "Dipole == very narrow band, highly resonant antenna", hence this question :) – Alexander Jul 02 '21 at 12:28
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    This is not going to have the same low-angle, directional cardioid pattern as a non-resonant, low end-fed Beverage antenna. However, there is a method of feeding a Beverage antenna made from 2-conductor feedline anywhere along its length that will. If I can find it, I'll probably post it as a new question. – Mike Waters Jul 02 '21 at 14:56

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If you feed a wire antenna at its center with open wire or balanced line, where the length of the antenna may or may not be designed to be resonant on any operating frequency, then the result is usually called a doublet antenna. A doublet’s length is usually chosen so that it isn’t anti-resonant (a full wavelength, etc.) on any of the desired operating frequencies, and is also typically fed with a tuner at the radio end of the feedline to present a reasonable SWR to a transmitter, or more efficient impedance to a receiver.

If you want to use coax feedline with balanced dipole lengths that are not resonant at your operating frequencies, then you may need a remote tuner at the center feedpoint (or some other impedance matching methods as part of the feed system), or else the coax losses can be very high (potentially multiples higher than balanced or open wire).

hotpaw2
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I think this is the wrong question. You ask does antenna X exist, but what you really should be asking is Given this configuration, can it be made resonant with a good SWR.

Random wire antennas exist. All you need to make anything work is a good antenna tuner. Of course, this doesn't guarantee efficiency, radiation pattern, or that it radiates at all. And possibly methods other than an antenna tuner might be more effective.

Best way is to try it. Even if the theory says it won't work well, as long as the radio is not overloaded with high SWR, it likely will do something.

user10489
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  • +1 for "...radiation pattern...". His antenna as described will not work like a Beverage antenna. A Beverage antenna is non-resonant, and only requires fixed impedance-matching transformers (rather than a variable tuner) to work on several bands. Perhaps you'd like to expound on that in this answer. – Mike Waters Jul 02 '21 at 23:07
  • Well, a beverage is also end fed and directional in the axis of the antenna away from the feedpoint. So you can't really do it center fed as far as I know -- you'd end up with two separate beverages? – user10489 Jul 03 '21 at 00:17