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

Sun Sep 25 17:37:57 EDT 2022

Dave, if you’d like to see a reasonably controlled test of radiators, you might want to take a look at the 2002 HF Pack Vertical Antenna Shootout Results.  The antennas range from full size to a resistor with a short whip.

https://www.qsl.net/hfpack/antennas/shootoutvertical2002.html#vertical

For sure, the counterpoise was a resonant horizontal quarter wave, not a drag wire, and not counterpoiseless (sic), but the results were otherwise controlled nicely for direction using quality gear by people fairly knowledgeable about portable and pedestrian mobile ops.  If you look at the numbers you can even (kinda) infer the radiation resistance goes up with the square of the radiator length thing, as one would expect.

And while there is no AX-1 tested, there is one antenna very much like it in the mix, about the same length, same dimension loading coil, etc. (not judging here Wayne, feel free to rebut).  And it’s about 5dB down from a full size quarter wave under controlled conditions, not a surprising result.

About the only thing missing seems to be some practical use data (per Julia) comparing a drag wire counterpoise as actually used in the field with the Shootout’s single horizontal counterpoise, if someone hasn’t already done that. Given the interest at the time  I’d guess that answer might exist in HF Pack lore too - maybe someone here knows?

Scott ka9p

Make something good happen!

> On Sep 25, 2022, at 3:26 PM, David Gilbert <ab7echo at gmail.com> wrote:
> 
> 
> 
> Personally, I only care about a pure comparison test in as controlled circumstances as possible.  Any practical test like you describe will have so many variables that it won't be useful for anything other than as an anecdote.  "Ground" is going to be wildly different depending upon location.  Propagation is highly variable for distant reports, and if you instead use a nearby setup for reception, it will make a difference which direction is it relative to the trailing counterpoise.
> 
> Besides, lots of people have already proven they can make contacts with the scenario you describe, but nobody has a clue how efficient that might be or not be.
> 
> 73,
> Dave   AB7E
> 
> 
> 
>> On 9/25/2022 12:30 PM, Julia Tuttle wrote:
>> Hi Dave,
>> 
>> I think that's a proper comparison in a physics sense, but I don't think it fully represents how the AX1 is deployed in practice.
>> 
>> I would run both an ideal scenario -- the one you described -- amd a practical scenario -- something like a KX3 + internal batteries on a picnic table, AX1 on the bipod, and the counterpoise trailing down to and across the ground.
>> 
>> 73,
>> 
>> Julie
>> 
>> On Sun, Sep 25, 2022, 15:19 David Gilbert <ab7echo at gmail.com> wrote:
>> 
>> 
>>    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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