[Elecraft] KX1 - We need to develop the ideal antenna

Sun May 15 04:39:10 EDT 2011

This is what we used to call the "shirt button antenna" 'cos we used shirt
buttons as the insulators which saves and awful lot of work making them.
For light weight I would consider 300ohm ribbon for the feeder and a simple
choke/balun to the connector.  Crock clips rust in our wx and slide switches
eventually pack up, so, I'm thinking of bullet connectors next.
73
David
G3UNA

On 15 May 2011 04:40, Erik Basilier <ebasilier at cox.net> wrote:

> After using a 26 ft wire with counterpoise as well as vertical and
> horizontal Buddipole configurations, for the past year or so I have settled
> on a dipole with jumpers, and this is the best configuration yet.  KK5F
> beat
> me to suggesting it here, but I am chiming in because the subject is
> interesting, and details are worth discussing. Here are some details of
> mine:
>
>
>
> 1.       My insulators are rectangular pieces of Lexan sheet, cut to about
> 0.25" x 0.5" x 1.75". Each insulator has a row of 6 holes. The holes are
> just wide enough to pass  the male and female connectors, which are Molex
> pins with added shrink-wrap tubing to avoid wire breakage. The wire from
> each side is passed through 3 holes in a zig-zag fashion, and the
> connectors
> are joined hanging in the air, forming a loop of about 1.5" diameter.  This
> arrangement is easy to disassemble in the field, yet holds the wire
> securely
> without placing stress on the connection itself. It depends on the friction
> created between the shoulders of the holes and the wire insulation. The
> ability to disassemble without tools helps me when I want to remove the 80
> m
> sections, or make repairs or replacements.
>
> 2.       The wire I use is the extremely lightweight copperclad available
> from The Wireman, which is strong and has a tough insulation which is happy
> to be subjected to the sharp edges of the insulator. It is also stiffer
> than
> some other kinds of wire. I find that the insulators hold securely even
> with
> softer wire, and I don't expect regular pvc insulation to be a problem, as
> I
> never put much mechanical tension on the wire. I do think the copperclad is
> more efficient than tinned copper which should have more rf resistance.
> Don't know how large this effect is in practice, but every little bit helps
> with qrp.
>
> 3.       My feedline is RG-58 from my Buddipole, which includes a
> lightweight balun using beads. This can be purchased as a separate item.
>
> 4.       The configuration is inverted-vee, supported at up to 22 ft or so.
> At the bottom is the tripod plus short mast from the Buddipole, which is
> light enough to be carried in the field for shorter trips. This is from a
> few years ago. I understand that Buddipole currently only makes a heavier
> model tripod that is intended to support a small beam. In any case, my
> tripod is the heaviest part of the setup, and for a longer trip on foot I
> would leave it at home and use whatever I can find to support the pole. The
> tripod with Buddipole short mast provides about 8 of the 22 ft. The rest of
> the height comes from a Cabela's Crappie Pole which is quite a bargain at
> $20 or so, and extremely light. If I remember right it is a 16 ft model,
> but
> with the top section removed. (It will remove itself the first time the
> antenna falls over!). I had to make a custom piece to connect the crappie
> pole to the Buddipole mast.
>
> 5.       I store the antenna with feedline detached on two "Halo Winder"
> type spools designed for kite string. I don't remember which vendor I
> bought
> them from, but they were available in a variety of sizes, without string,
> easy to find on the net. I use the 5" diameter model which leaves room to
> spare with wire for all bands including 80 m.  Each spool with wire and
> insulators weighs about 5 oz. My center insulator is similar to the other
> insulators, and I detach the wire by unthreading the 3 holes on each side
> for transportation. A hole in the middle slips right over the crappie pole,
> and stops because the pole sections are conical. At first I used
> Buddipole's
> mini banana connections for the feedline, but the plugs were damaged when
> the antenna fell, so now the feedline is soldered and bolted to the
> insulator, with pigtails for Molex pin connection to the antenna wire. (I
> got a new feedline from Buddipole, since I still like to use the complete
> Buddipole in some situations where weight is not an issue.)
>
>
>
> Before I took this antenna into the field, I tried flexing the soldered
> copperclad to see if it would break. It would not. The steel core seemed
> very hard to break. Then, first time in the field, the KX1 ATU wouldn't
> find
> a good match, and it turned out the wire had broken right at a solder
> joint.
> That's when I slightly enlarged the insulator holes and added shrinkwrap
> tubing around the solder joints. It turned out that the wire still locked
> very securely in the holes.
>
>
>
> The Molex pins tend to get loose with use. Not a big deal, as they can
> easily be adjusted in the field with a knife and maybe a rock.
> Nevertheless,
> I still want to find better pins. I dream about gold-plated machined pins
> such as those found in some expensive military connectors or maybe top
> quality IC connectors/chip carriers. The ideal solution would include both
> the female and male parts, available without cannibalizing a multipin
> connector; the overall diameter should be small (1/8" or less) to slip
> through insulator holes, and the the pair should have enough spring
> force/friction to stick together when used without a connector shell.
> Anyone
> know a source?
>
>
>
> I have long toyed with the idea of trying traps, especially for the 20/30
> switch point, where the trap should be very light and not have all that
> much
> reactance to influence the bandwidth at, say, 80.
>
>
>
> Overall I like this antenna so much that I have toyed with the idea of
> making them for sale. Just kidding.
>
>
>
> 73,
>
> Erik K7TV
>
>
>
>
>
> KK5F wrote:
>
>
>
> The approach that I found worked best for me was an antenna that was a
> full-length 40m dipole (66 feet), with each leg broken in six places with a
> home-made PCV tubing insulator with integral jumper and clip so that the
> appropriate length dipole can be established for all seven HF bands between
> 10m and 40m.  I built the antenna for all these bands for use with any rig,
> not just the limited coverage of a K1 or KX1.  It works better than any
> other antenna I've ever used in a field environment.  It typically takes
> less than a minute to alter insulator jumper configuration to switch to
> another band.  It meets *all* of the desired criteria listed by Bob, to
> which I would add "5.  Is very inexpensive and quick to home-brew."  (I
> have
> a pdf file with construction details, diagrams, and photos that I'll e-mail
> to anyone on request.)  I use the technique that you suggest of attaching a
> 33-foot segment to each leg for 80m operation, which is rare for me.
>
>
>
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