[Elecraft] AX1 Loaded Whip Antenna - Elevation and

[David Gilbert]

I think users of the AX1 would be better off thinking of IT as the 
counterpoise, and making the most out of what they normally consider to 
be the counterpoise wire.

Look at it this way.  Unless you have a lot of current on the shield of 
the coax (in which case IT is doing a lot of radiating), roughly equal 
currents are going to try to go both ways from the feedpoint ... into 
the AX1 and into the "counterpoise" wire.  The AX1 is typically 
physically shorter and it certainly has more loss, and since the 
radiated field is a function of net current and length, in most cases 
the counterpoise wire is at least trying to do the most radiating.  I 
say "in most cases" because the typical position of the counterpoise 
wire puts it along the ground or near some other RF-sucking structure.

In my opinion, probably the best way to use the AX1 is to put the 
counterpoise wire as straight, high, and in the clear as possible and 
let the AX1 act like the shortened other half of the circuit (i.e., the 
counterpoise).  If that isn't possible, make the counterpoise wire as 
straight and vertical as possible ... climb a tree and let the wire hang 
down.  ;)

If I had a good EZNEC model of the AX1 I'm pretty sure I could prove 
that assertion, but for those who have an AX1 I'd bet some field 
strength experiments would bear me out.

I'm not saying that the AX1 isn't a worthwhile investment, and I'm not 
saying it doesn't radiate.  I just think there are some misconceptions 
on what it's actually doing and how to best make use of it.

73,
Dave   AB7E




On 8/26/2019 3:51 PM, MaverickNH wrote:
> I brought along a NanoVNA this trip and used it to array the two counterpoise
> attached to my AX1 antenna - adjustments of counterpoise brought SWR down
> from 9+ to <2. SNRs in the low ‘teens with a 200mW WSPRlite vs upper 20s -
> *inside* a hotel room with sealed windows.
>
> As Wayne said, the AX1 is particular wrt configuration. When it’s good, it’s
> very, very good, but when it’s bad, it’s terrible. The NanoVNA is pretty
> cheap/light kit to add if you’re not bringing an ATU-enabled rig.
>
> Bret/N4SRN