You're talking about a horizontal pair of AX1's ... I asked about them
oriented vertically. That wouldn't require them to be as high above
ground as you mention and would still allow them to be carried
pedestrian mobile.
I modeled a vertical pair at the same height above ground (15 feet) as I
did before with a 13 foot hanging counterpoise wire simply to make a
semi-valid comparison. According to EZNEC, two 4' loaded whips oriented
back to back were down anywhere from 4 to 9 dB from a single loaded whip
with the hanging 13 foot counterpoise, but not surprisingly that was
heavily dependent upon what assumption I made for Q of the coil.
Since most pedestrian mobile operations would involve at least half of
the 13 foot counterpoise wire being dragged along the ground and
therefore less effective than if all of it was oriented vertically like
I modeled it, I suspect that a single AX1 with the counterpoise and two
AX1's oriented as a vertical dipole would be similar in performance.
The single AX1 would of course be simpler, less expensive, and easier to
carry while operating.
As an aside, it seems to me that AX1 or similarly loaded short whip with
a trailing counterpoise wire is probably the most efficient setup for
pedestrian mobile. For fixed portable operation (camping, SOTA, etc), I
would probably go for whatever larger configuration I could easily carry
and setup quickly ... such as that full sized portable vertical antenna
I mentioned in an earlier post. I think it would have a significant
field strength advantage. I might even build two of those portable
verticals just to find out how much advantage compared to a short loaded
whip with a counterpoise.
73,
Dave AB7E
On 9/29/2022 4:14 AM, Wayne Burdick wrote:
We studied this. To provide any advantage over a vertical AX1 with a single
counterpoise wire, an AX1 dipole would have to be well over a quarter
wavelength above ground, with both halves tuned to resonance, and fed with
low-loss coax and a balun or balanced feedline. Even then the advantage is
small and only in the dipole's broadside directions.
That said, a pedestrian-mobile version of the dipole held a few feet above the
operator's head would eliminate the dragged counterpoise. I'd be concerned
about nearby trees and ogling passersby.
73,
Wayne
N6KR
On Sep 29, 2022, at 4:05 AM, Rich WC3T <[email protected]> wrote:
Interesting idea.
72,
Rich Hurd / WC3T / DMR: 3142737
Grid: FN20is
Bureaucracy is always in search of self-preservation. — AA7BQ
On Sep 29, 2022, at 04:14, David Gilbert <[email protected]> wrote:
Has anyone ever tried to used two AX1's back to back as a vertical (not
horizontal) dipole? And if so, how did its performance compare to a single AX1
with the 13 foot counterpoise wire?
Just curious.
73,
Dave AB7E
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