Best wire antenna for 40 meters?

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Joe Word:
What wire antenna will have the best performance on 40 meters, a dipole, a G5RV or a Carolina Windom? Or what wire have you found that works the best?
Thanks, Joe

Is the antenna primarily for DX chasing at night, or daytime local work?

How big is your yard?

What kind of supports (natural or man-made) do you have, and what are the relative positions of the natural supports?

How high can you get the antenna?

Do you want gain in specific directions at the cost of having less signal in other directions?

Do you have much man-made QRN at your location?

What's the ground conductivity like in your area?

Steve Katz:
It surely does depend on what you're trying to do with that wire...

...a low doublet, whether it be a dipole, a G5RV or a Windom type (off center fed dipole, or OCFD), will work quite well "locally," within a few hundred miles.

That same antenna (whichever it is) substantially elevated, say, 65' above ground or higher, will start to become an effective "DX" antenna, good for worldwide contacts at night, but will do so at a slight loss in "local" effectiveness.

That same antenna oriented vertically (center fed vertical dipole), which of course might be quite a trick with a 66' long doublet, will have an even lower radiation angle and become an even more effective "DX" antenna, at the considerable sacrifice of local effectiveness.  In fact, I use a vertical on 40m most of the time and work into Africa better than I can locally -- but that's a fact of life with vertical antennas.

A 1/2-wave, resonant (by definition) dipole can be fed with coaxial cable and no antenna tuner, and should match up quite well and require no tuning.  A G5RV (102' doublet fed with a matching section of ladder line spliced to coaxial cable 30' below the antenna) is non-resonant on 40m and almost always requires a tuner.  The OCFD, or at least the "Carolina Windom" sold by RadioWorks, is 66' long and seems like it should be resonant, just fed in a funny place.  I have no idea why this would be more effective than an ordinary center fed, resonant dipole.  A real "Windom" antenna has no center insulator and is not fed with coax...the original design was an off-center fed horizontal wire, tapped 1/3 from one end (dimensionally), and fed with a single wire to form a top-loaded Marconi that had both vertical and horizontal properties.  I understand the basis for that design; I do not understand the basis for an off-center fed dipole having unequal length legs and a coaxial transmission line.  Maybe that's just me!

For a given aperture, any number of antenna designs will work about the same way, with the major variable being the installation (height above earth, orientation, etc).  I can take a 66' long center-fed dipole and make it a super DX antenna (by installing it vertically), or a great "local work" antenna (by installing it low, and horizontally), or most anything between.

73 de Steve WB2WIK/6

Pete Allen:
HI Joe: First, either the off center fed dipole that we commonly call a Windom or a center fed dipole will do you a nice job on 40 at the typical (low) heights most of us get to hang antennas.

  The OCF dipole is really a multiband antenna that does not give much away on bands above the band it is cut for. The feedpoint is chosen to give a reasonably low SWR using 50 ohm line on the fundamental and the harmonics, something a center fed dipole lacks. As far as fundamental frequency performance is concerned, it's just another dipole.

  The center fed dipole has a reasonable SWR on the fundamental frequency and the ODD harmonics, so a 40 meter dipole works pretty well on 15 but not at all well on 20 or 10. In fact, if it weren't for transmission line losses most "wide range" tuners could not "tune" a dipole on its even harmonics.

  The "full size" G5RV is touted as an all band wonder, and the truth is that it works fairly well on 40 and up provided you have a wide range antenna tuner and you are willing to put up with the coax losses. On 160 and 80/75 the G5RV is about like the antennas that come packed with HT's. Leaky dummy loads but better than nothing.  

   And if DXing is your game - go with a vertical and either a good radial field or an elevated radial field. You will be much happier. But don't neglect the radials or you will be really unhappy with the results.

  73  Pete Allen  AC5E

Joe Word:
Thanks for the responses.

The use will be local/state side not DX.
The wire will not be vertical.
Height will be a max of 40'.
Length a max of 132'.
Can use the built-in antenna tuner in my IC-746 if needed.

The main question is, will any other wire type antenna out perform the dipole given the above constraints?

Thanks, Joe


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