I agree with what Jim wrote.
The evaluation of an antenna is a process over a period of time, not a
couple of measurements or a computer model.
I wanted to find out how well a good loop really works.
I bought my AMA-8 loop in about 1995 and paid over $1000 for it.
I didn't need it, I only wanted to find out how well a good loop really
works.
I ran a test for one weekend, which is not quite what Jim was talking
about...not long enough to be a conclusive test, but I was able to get a
first impression.
I mounted the 6' diameter loop on a 10' aluminum pole (so the bottom of the
loop was 10' up).
I set up my Ten-Tec Argosy just under the antenna.
I spent two days testing on 40 and 20m, comparing to my 40m dipole which was
fed with a short run of 300 Ohm transmitting twinlead, and matched with a
BIG ANNECKE link coupler. The dipole was mounted with its center about 10'
above a 3 story house, with the ends slightly sloping. I used it on 40 and
20m for the test. Of course I did have about 60 ft. of additional coax
(Aircell-7, similar loss to RG-213) running out to the yard where I was set
up.
I kept a log of lots of stations received and several worked, using A/B
tests.
I filled a couple pages in a logbook. Then scanned it in as a PDF document.
Unfortunately I don't find the log right now. It is somewhere in my
computer.
So is every file I've ever had since 1995. That's what makes it hard to
find.
My first impression was, the loop worked as well as the dipole. I could
find stations sometimes that were stronger on the loop, because I could
rotate it. Most of the time it was a wash. A blindfolded listener given
the choice between the two, without knowing would probably say, give me
either one.
OF COURSE the dipole was broad-banded and I had to constantly re-tune the
loop, which is a pain in the assets.
So how good was the 40m dipole?
Fair question.
A year later, a young friend of mine (DL6RDR) worked CQWW CW from my QTH
using my Argonaut 509.
I was in Luxembourg for the contest.
He used this same 40m dipole on 80 and 40 meters.
He turned in the second highest score in all of Europe in the QRP class, so
it would be hard to argue that the dipole does not work.
BTW, for 20/15/10 I had an 8-el. Cushcraft LP on a 33' tower - max height hr
in DL without getting a building permit.
"Good" loops work.
People who claim they do not are either speculating, or they have never used
a good one.
Good ones cost a lot of money. Over $1000 if they are to cover 40m.
People simply do not understand just how much loss there is in the
connections of the various components.
On the good loops, everything is huge and welded together.
My homebrew loops using coax as the main loop, also work, but don't come
anywhere close to the performance of a good loop.
However I can take them apart, fold them and transport them on a motorbike.
Can't do that with a big loop.
In the late 80s I built a 20m QRP transceiver, 2w CW.
When I finished it, I set it up on the living room table in my house, with
my folding (coax) mag loop next to it.
There was some contest going on.
I worked about 50 stations around Europe in about an hour running this
setup.
I was as thrilled as I would have been if I had worked Spratly and Navassa
on the same day using the big rig!
Normally I do not use mag loop antennas. I don't have to.
But I wouldn't hesitate for a second to use one if I were in a situation
where I could string no wires!
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Jim Brown
Sent: Sunday, April 27, 2014 10:58 PM
Again, you won't know until you do serious comparisons with other
antennas, between many stations, at the same time, and average a LOT of
such data. Until you do that, it's no more meaningful than if you say
you called someone and he came back to you. :)
73, Jim K9YC
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