It's not the takeoff angle that makes the difference here. The takeoff
angle of a half wave vertical dipole over real ground is not much
different than the takeoff angle of a quarter wave (or shorter) vertical
fed against a ground plane or counterpoise.
I'm pretty sure that what's really going on here is that as you make the
counterpoise wire more vertical the counterpoise is becoming the primary
radiating element The AX1 essentially becomes a loaded "counterpoise"
for the vertical trailing wire. I wouldn't be surprised if the
counterpoise wire does most of the radiating even if trailed across the
ground, although much of it would be lost to the lossy earth and the
rest pointed upward. If we were able to model the AX1 with the
counterpoise we'd most likely see that the integral of current as a
function of length for the counterpoise wire exceeds that of the AX1,
and if the AX1 was vertical and the counterpoise horizontal most of the
radiated energy would be horizontally polarized. Somebody could easily
prove (or disprove) this with a short sense antenna and a field strength
meter.
I suspect lots of people won't like this perspective, but there it is.
73,
Dave AB7E
On 5/29/2019 1:52 PM, Adam Goler wrote:
I also anecdotally observed greater propagation with the counterpoise wire
hanging vertically this past weekend.
Intuitively, using a vertical counterpoise, as the "feedpoint" increases in
height away from the ground plane of the Earth, the takeoff angle should
decrease as the radiation pattern more and more resembles a free-space
vertically oriented dipole field (picture a field shaped like a donut).
----------------------------------------------------------------------
Message: 1
Date: Tue, 28 May 2019 13:24:03 -0400
From: Hank <h...@optilink.us>
To: VE2PID <ve2...@videotron.ca>, elecraft@mailman.qth.net
Subject: Re: [Elecraft] [AX1] Who has the AX1 antenna DX record?
Message-ID: <5bd0e4be75154c7f58e74eb7ee1b7...@optilink.us>
Content-Type: text/plain; charset=UTF-8
Good info!
I have noticed from operating in the field that I make more contacts if I
lay the counterpoise along the ground. ?I get better signal reports from
stations in the direction of the counterpoise.
I noticed from operating this weekend at an overlook that with the
counterpoise over the side of the overlook going down hill at roughly 30
degrees, my contacts were clustered farther away - again in the direction
of the counterpoise.
I was operating on 20 and 17 with the AX1, KX3, SSB at 15 watts.
Hank
K4HYJ
?
----- Original Message -----
From: VE2PID (ve2...@videotron.ca)
Date: 05/28/19 11:30
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] [AX1] Who has the AX1 antenna DX record?
... I used the AX1 as a test in WPX CW last weekend for only an hour on
a picnic table. No problem ...in that time I got 13 QSOs from FN45
including FL. (10 Watts KX2, 13' counterpoise).
--
After NEC simulations (0.005, 13 average ground) , we find how the gain
is maximized in the direction of the counterpoise. On 20 meters, if the
wire is horizontal at 4 feet height, the take-off angle is about 56
degrees. But if the wire goes down from 4 feet to the ground (15 degrees
slope), the F/B is less but the take off angle is lower at 35 degrees
(Image at https://i.imgur.com/XKPjM8T.jpg )
73, Pierre VE2PID
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