Why would I replace the wire with a resistor? I was talking about
replacing the AX1 with a resistor and keeping the wire.
I have no doubt that an AX1 without a wire hears better than a resistor
without a wire, but that's mostly because the resistor provides a better
match and can't rely on body capacitance or the coax shield.
If the AX1 was less expensive I'd buy one and do the tests. I may be
totally wrong, but I still say that ANY tuned short whip with a
counterpoise is doing most of the radiating from the counterpoise.
73,
Dave AB7E
On 9/21/2022 7:59 PM, Wayne Burdick wrote:
Dave,
I've done many variations on whip antenna tests.
A resonant 4' whip with or without a counterpoise is on a different planet from
a resistor. If an AX1 were listening in on this conversation, it would
challenge you to a duel, with live ammo :)
In fact the counterpoise is absolutely required for transmit, but you can get
away without it on receive, where body capacitance to ground alone will
suffice, even on the HF bands.
Try this test: Go outdoors and connect an AX1 (or equivalent) to the antenna
jack of any 20 meter receiver. With r without the counterpoise You'll get of
noise, lots of signals.
Now replace the wire with a resistor.
Nothing.
QED....
Wayne
N6KR
On Sep 21, 2022, at 7:29 PM, David Gilbert <ab7e...@gmail.com> wrote:
Well, the reason I mentioned the 50 ohm resistor is that a year or so ago
somebody on this reflector mentioned that he did a direct comparison between an
AX1 with the recommended 13 foot wire counterpoise and with no counterpoise at
all. I don't remember for certain but I think he said he used the RBN. I do
remember that he said the difference in signal strength was about 30 db. For
grins I used EZNEC to model a single 50 hm resistor 15 feet off the ground with
and without a 13 foot wire hanging from one end of it. I got 30 db difference
in calculated signal strength.
I am by no means claiming that is a definitive or even relevant test ... I just
think it would be interesting to actually do an empirical comparison.
It is my opinion, however, that most of the radiating on an AX1 (or any other
short loaded whip) is being done by the counterpoise wire and/or the shield of
the coax. The coil and whip are matching aids. If so, it's possible that a
resistor would accomplish the same thing. ;)
As I said, I'd be willing to do the comparison if anyone is willing to lend me
an AX1. I'd be happy to be proven wrong.
73,
Dave AB7E
On 9/21/2022 6:46 PM, j...@kk9a.com wrote:
Thomas Schiller, N6BT once wrote an article titled "Everything Works". In
the article he discussed how he worked all continents on CW (a mode that you
can actually hear) using a light bulb antenna during the ARRL DX contest.
The AX1 appears to be a 45" whip with a base inductor made of 20AWG wire. I
am not sure what is inside the base, if anything, to bring the impedance up
to 50 ohms. With some sunspots, I am sure that it is fun for pedestrian
mobile use which is what it's designed for. A 1/2wl dipole or 1/4wl vertical
will be a much better radiator.
John KK9A
David Gilbert ab7e wrote:
A comparison to any other antenna would be useful. A comparison to a 50
ohm resistor with a similar counterpoise wire would be even more useful
as a baseline measurement. If anyone wants to lend me their AX1 I will
do that.
73,
Dave AB7E
On 9/19/2022 10:33 AM, Ron Gruner wrote:
I've been impressed by how well my little AX-1 whip antenna performs on 20
meters. Here's a photo of the rig: https://gruner.com/k4rhg/andover_ma.png
and the propagation map:
https://gruner.com/k4rhg/wspr_2watts_sep16_2022.png
A friend, Derek Rowell (AK1WI), gave me a two-watt WSPR kit he had
designed
-- easy and fun to build. I connected the unit to the AX-1 sitting in a
window sill facing west and strung the out-of-the-box counterpoise over a
lamp shade and bed headboard. No idea what the SWR is, but it must be
pretty good.
I immediately began receiving propagation reports and within 24 hours had
reports from 240 unique stations. The farthest was VK5ARG (17,276 km) with
a SNR of -21. Even though the window faced the west, propagation into
Europe was strong with SV9KI (7,800 km) reporting -26 SNR. The
propagation report is from http://wspr.rocks/ <http://wspr.rocks/>
I've found that WSPR is a great way to evaluate antennas. The AX-1 seems
to be performing very well.
73,
Ron Gruner
K4RHG
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