[Elecraft] [KX3] Miniature self-supporting HF antennas

Wed Jul 22 11:20:48 EDT 2015

     To add to the small self-supporting thread - loads of great
contributions there, thanks everyone - : I travel a lot for business, and
often carry my KX3 + Alexloop which is pretty much the only kind of antenna
that I know I'll be able to use in urban areas. This setup works really
well: on my last trip to France, I was able to do lots of digital QSOs all
over Europe, as well as several countries on phone on 20m. And I also had a
couple of QSOs on 40m with French hams who could hear me fairly well in a
large part of the country - not everywhere though, 5W on a 1m diameter
magloop on 7MHz only takes you so far.

    I am in Dallas TX right now, and I spent time on 20m phone last night:
59 reports from Georgia and Montreal, CA, with a long QSO with two very
friendly hams from Canada. We even had two guys from Reunion Island join us
- one of them could not hear me, the other said he could, then band
conditions changed and everyone drowned into band noise before I could
complete the QSO... that's the life of a QRP operator.

    When I know I can operate outside, a Sotabeams fiberglass pole with
thin wire and a 9:1 Unun (http://www.aerodynes.fr/2014/05/18/peanut-balun/)
do a nice job, but they are impractical in cities, of course.

    Only circumstantial evidence, I know, and anyone can do a QRP phone QSO
around the globe if conditions are just right, but still, I have tried
quite a few 'hotel room' setups, and right now, Alexloop/KX3 is really my
favorite. Now, if only more North American hotels allowed their guests to
open their windows...

     My two last points:  1) I'm tempted to build an autotuner for the
AlexLoop, I have a couple of ideas on how to do this very simply, stay
tuned (pun intended). 2) Even on a Magloop, the PX3 is useful, and I would
like to make the PX3 battery operated as well. There is definitely room in
the box, and looking at the PCB, there is a connector inside just for that
purpose, right Wayne ?

73 de Ed W6ELA

On Sun, Jul 19, 2015 at 11:45 AM, Wayne Burdick n6kr at elecraft.com [KX3] <
KX3 at yahoogroups.com> wrote:

>
>
> Hi all,
>
> Have you found the "perfect" above-the-treeline backpacking antenna for
> use with your KX3 or other small rig? I've used everything from a 10-meter
> coat hanger whip, to a yagi that breaks down into two dozen pieces, to a
> dipole held up at the center by a willing (and tall) campmate. The variety
> (and price range) of such antennas is staggering.
>
> I've had pretty amazing results using short, base-loaded antennas on the
> higher bands--especially when conditions were good. My personal best is JA
> from W6 on 15-meter SSB, running 3 watts to a Maldol 48" whip. These
> antennas collapse and break down into just two pieces, taking very little
> space in my lightweight go-bag. This leaves room for a couple of 25' wires,
> adapters, and weights for times when there are trees available.
>
> But the search for the ideal miniature HF antenna continues: something
> both very compact *and* highly efficient. Ideally it would break down to a
> length of 8" or less, do an excellent job on 20 meters and up, and earn a
> passing grade on 30 and/or 40 meters.
>
> One other key factor, at least with the KX3/KX1/K1 genre, is to take
> maximal advantage of the rig's internal ATU. A wide-range ATU (such as the
> KXAT3) can turn a narrow-banded antenna into one that covers a full band or
> even multiple bands, within limits. One general approach is to coarse-tune
> the antenna's own inductance, then let the ATU do cleanup.
>
> Is the best antenna for backpacking a very small magnetic loop? A cleverly
> designed, center-loaded telescoping whip? A length of #30 wire lofted by a
> small helium balloon? (Or, more intriguingly, some combination of these?)
>
> I'd be interested in hearing about your antenna theories and field
> experiences, backed up by entertaining fish stories, if they aren't
> embellished to an embarrassing degree. If your supporting documentation is
> too voluminous for the forum (attached photos, etc.), feel free to email me
> directly.
>
> If anything substantive or surprising emerges, I'll do a followup posting.
>
> 73,
> Wayne
> N6KR
>
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> Posted by: Wayne Burdick <n6kr at elecraft.com>
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