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

[Howard Hoyt]

Hi all,

Over at the Elecraft-KX io group, being QRP all the time we had this 
discussion a while back and I wanted to repost a post I made with a 
useful link, I think it is germane to this discussion:

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https://elecraft-kx.groups.io/g/main/topic/90090191#72021

posted by Howard Hoyt - Mar 28, 2022 #72021

Hi all,
I thought I'd start this thread since some posts regarding antennas in 
general were pretty much OT.  Subjective reports we see in groups all 
the time although great for expressing enthusiasm for ham radio 
operation in general, carry little information others can use to 
evaluate antenna performance.

Like many other hams I studied Maxwell's equations in EE school (too 
many years ago), and they define the characteristics of electromagnetic 
waves pretty thoroughly.  I am sure modern antenna engineers utilize 
them to perfect antenna designs and many hams may be talented enough to 
use this approach.  However this many years after Uni. I only have the 
time and brain power to use more cookbook approaches, and like many 
people I learn faster with visual aids.

With this in mind, and specifically regarding the oddly controversial 
aspect of two-pole radiation (radiator and so-called counterpoise) I 
wanted to share this YouTube video by Frank Rutter / K3AW:
https://www.youtube.com/watch?v=LEigIMS6bo4
He does a masterful job of presenting many aspects of antenna 
performance using a 3 GHz model, which has a wavelength short enough to 
allow the antenna and ground plane (counterpoise) to fit on a table for 
demonstration.  I highly recommend setting aside an hour, grabbing a 
beverage and watching the entire 1:08:27 video, it may be the best 
expenditure of your time this week.  My single critique of the 
demonstration is I wish he had a big meter to show the signal changes as 
he changes the setup.

Relative to recent discussions regarding counterpoises here, Frank shows 
how a lossy counterpoise (his model for earth) diminishes antenna 
performance at the 10:00 mark.  At the 30:00-minute mark he explains the 
proliferation of stacked beams.  At 1:03:00 he explains that an inverted 
"L" can result in RF at the operating position, due to common-mode 
currents.  This Inverted "L" configuration resembles how many portable 
end-fed antennas end up being deployed due to necessity.  Also he 
demonstrates how at commonly deployed heights they show a propensity for 
high-angle radiation, good for close in to medium range communications, 
not so much for DX.

Part of the value in Frank's demonstration is the relative, but direct 
comparisons of the different antenna configurations in identical 
locations.  We do not have this luxury when operating from a hilltop or 
at the beach, so we have to apply best practices to maximize results, 
and in this way ideas from his demonstrations can be valuable to us.

As an additional note: I have learned a lot about designing antennas by 
modeling them using EZNEC.  After years selling and supporting the 
software, Roy Lewallen / W7EL has given the package to us for free and 
available here:
https://www.eznec.com
I highly recommend getting this software and learning to use it.  If you 
are truly interested in maximizing your antenna knowledge and 
performance, it will be time well spent.
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Cheers & 73,
Howie / WA4PSC