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
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