[Elecraft] AX-1 -- with and without counterpoise

[David Gilbert]

To be a proper comparison, the AX1 needs to be out it the clear away 
from anything else, preferable at a height that allows the counterpoise 
to be hanging straight down with the end maybe a foot or two off the 
ground.  Measurements should be with the AX1 at the same height above 
the ground without and without the counterpoise. Ideally a KX2 or 
similar rig should used, be battery powered (with very short leads if 
external), no coax, and no body contact to the source of RF.  Signal 
reports should be in microvolts ... the number of contacts isn't really 
useful and neither is SNR if the readings are taken over a lengthy 
period of time.

If I can get my hands on an AX1, I plan to either climb a tree or set up 
a tall fiberglass step ladder for the AX1 as far away line of sight from 
my home as practical.  I'd use my KX2 for the signal source, using the 
Tune function to put out RF without touching the KX2.  Near my home I'd 
set up the portable vertical antenna I described in an earlier post, and 
feed that to my K3 set to read microvolts.  I'd operate the AX1 (with 
and without counterpoise wire) and any other antenna for comparison, and 
have a friend record the microvolts from the K3 as a blind test.

I would use the tuner in the KX2 to simulate actual use, but that would 
of course introduce a variable for possibly different amounts of loss in 
the tuner depending upon the load.  I don't see a good way to avoid that.

73,
Dave   AB7E



On 9/25/2022 7:06 AM, Ron Gruner wrote:
> I've just run two tests of my WSPR/AX-1 set-up with and without a
> counterpoise. Each test ran 24 hours over the last couple of days. Here are
> the results:
>
>                                                      COUNTERPOISE?
>                                YES       NO
>                            -------  -------
> Total Contacts                152      129
> Maximum Distance (km)      15,720   17,276
> Median Distance             2,137    1,823
> Median SpotQ                  446      398
>
> Where SpotQ = Kilometers / [(2 Watts x (SNR in DB + 36))/36) ]
>
> The WSPR circuit's ground and SMA connectors are apparently providing
> enough of a counterpoise to propagate a respectable signal.
>
> Here's a close-up of the rig with no counterpoise:
> https://gruner.com/k4rhg/wspr_ax-1_nocounterpoise.png
>
> 73,
> Ron Gruner
> K4RHG
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