This discussion makes me wonder if the ARRL Handbook and the ARRL
Antenna Book have somehow been banned! This is BASIC antennas, guys.
This is not CB radio, it is ham radio, and we're supposed to be able to
study this stuff and figure it out! Building antennas is one the
easiest parts of ham radio to do yourself, and once you've invested the
time to learn the fundamentals, it's a lot of fun!
New copies of these books can be bought for less than the cost of the
overpriced antennas mentioned here that mostly don't work very well,
while the cost of the wire to build much better antennas can be had for
a few dollars! Wire as small as #22 works fine for temporary wire
antennas for QRP operation. Insulators are easy to improvise with piece
of plastic with holes drilled in them.
While we can make a wire of random length load (take power) and radiate,
it's far easier if we make it a quarter wave. "One size fits all"
antennas are like "one size fits all" clothing. They work, sort of, but
FITS (and LOOKS) a heckuva lot better.
The most expensive part of a vertical for portable or hiking operation
is whatever you use to hold it up. I paid about $100 for a 10M long
telescoping fiberglass pole that collapses to 1 M. Tape the wire to it,
run out a couple of radials, and you've got a great antenna for any band
between 40M and 10M (just trim the wires to a quarter wave on the band
you want to work). For less than $10, you could do the same with 2-3 10
ft lengths of 1/2-in PVC conduit.
The picture of me on my qrz.com page is from our Chicago club's annual
QRP night in a local park My antenna was #22 wire wound on that 10M
pole, the pole was wedged between the seat and the top of the picnic
bench so it was at roughly 45 degrees to vertical, and I had one or two
radials laying on the ground. In a few hours, I made a half dozen QSOs
on 30M, including busting a pileup. A few years ago, W6GJB and I set up
on a peak near Sacramento with a KX3 running on internal AAs into a
similar antenna for 15M. We worked three continents in about 10 minutes.
There were two radials laying on top of low brush. The vertical element
was held up by a small tripod intended for a small camera.
Nothing personal intended, but my opinion of virtually all of these
antennas you buy comes under the heading of "a fool and his money."
73, Jim K9YC
On Thu,9/29/2016 12:50 PM, Holger Schurig wrote:
Hi all,
I have an end-fed antenna with some random wire. The UNUN at one end of it
has three sockets to plug the random wire in: 1:4, 1:9 and 1:16.
My KX3 has the built-in ATU.
I now want to find out on which band I best use which one of the sockets.
As a first step, I wrote a simple program kx3lc.py (see
https://gist.github.com/anonymous/5d53f5bdbc50782a9d5e2c8d7062be69) that
can give me an output like this:
holger@laptop:/usr/src/afu/kx3/swr$ ./kx3lc.py
L: 0.12 mH, C: 203.0 pF on transmitter side
Am I right to assume that the ATU settings with the lowest L is always the
best? So when I have (for the three sockets), these values,
L: 0.12 mH, C: 203.0 pF on transmitter side
L: 0.0 mH, C: 246.0 pF on transmitter side
L: 0.0 mH, C: 256.0 pF on antenna side (but lowest SWR 1.2-1)
... that the middle socket is the best?
73
Holger, DH3HS
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