KX-1 - Simple 4-band antenna

[Albers-2]

About 3 years ago I built KX-1 #608 with KB-30 and KXAT1. I've had tons of fun with operating it in my travels at relatives' homes, hotels, resorts and campgrounds. Usually I use the simple 24 ft wire recommended in the KXAT-1 manual, supported on whatever I can get, with three ground radials laid out wherever I can.

But sometimes I like to try using a bit more wire. My friend K3MT, who designs antennas for a living, has a simple three-step recommendation for us hams: 1)get as much wire as you can; 2)as high in the air as you can; and 3) get as much RF current into it as you can. I let KXAT-1 take care of number 3, and I figure 1 and 2 are up to me.

So I made a 50-footer. Radio Shack sells a spool of speaker wire - 16 ga, clear plastic insulation, 50 ft ($9.99 in their catalog). Now, your results may vary, but I measured my antenna today it it turned out to actually be 51 ft 9 inches. I tied a knot about 2 ft from one end, just to keep the wires together for convenience. The rest of the wire I un-zipped, so I have two wires each just shy of 50 ft long. The RS wire has a white stripe running down one conductor to help keep polarity straight but rather than relying on that, I tied a loop in the free end of one wire and crimped a spade lug with red insulation on the other - I call this the radiator wire. I found a nice BNC-to-binding post (two poles) at a hamfest, and that (along with some nylon twine to hold things aloft) completes my portable antenna.

This week I finished building the KXB-3080, and I wondered whether good ole KXAT-1 would match the above antenna on all four bands. The answer is a resounding yes!

Yesterday and today I ran some tests out in the back yard. I tried three different configurations for the radiator wire:
1) high end into a tree, about 20 ft up, with the end in contact with the leaves a little, sloping down to the operating position.
2) same but high end up about 40 ft, stopping just short of the leaves.
3) radiator iwre running straight up for about 8 ft, then sloping upward to the 40 ft high point.
(for 1 & 2 I was sitting low to the ground on a beach chair for the tests, for 3 I had the radio on a low table.)

As for the counterpoise wire, I tried each of these configurations with the wire laid straight out toward the tree (i.e., running in the same direction as the radiator wire) and also with said wire running in the opposite direction. I did not try many non-straight-line deployments of the counterpoise, just one with configuration #3, with the counterpoise laid out in a zig-zag about 15 ft per leg. I did almost all the tests at low power, using the internal battery. I did one series using a 12V gel cell, and saw essentially no difference.

I was thinking about providing the results in tabular form, but I won't, because there really weren't significant differences among the configurations. Suffice it to say I tested each of the above configurations on 3560, 7040, 10106, and 14060 and every time the SWR as indicated by the KXAT-1 was either 1.0 or 1.1.

I don't know whether results would vary if you got a spool that was only 50 ft instead of 51 3/4 ft, but I doubt it.

73
Ray K2HYD
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