Preparing the KX1 for SOTA battle

Hi all,

Elecraft KX1

A few months ago I picked up a KX1 from a EDMRC club member who was selling. The unit came built and fully equipped, with the inbuilt ATU, the 30 and 80 band board and the keyer. The KX1 is a CW only rig but designed especially for portable use. With my mountain goat status out of the way, I wanted a CW specific and more light weight setup.

Rik VK3EQ (VK3KAN) had shown me a very lightweight squid pole at the 2013 Gippstech. I was quite interested in this because it packs up to 60cm in length. It has a 4.7m length when extended. Perhaps the top segment is too light duty to hold anything but a vertical wire, but the next segment down should handle at least a lightweight inverted V configured wire.

Random length wire antenna

Elecraft recommend that the KX1 ATU unit be used with “random length” wire, so long as the wire is not 1/2 wave length on the desired band. Note the reason for this is that the internal tuner is not always able to match the high half wave impedance.

I decided I wanted something serviceable on 20/30/40. After looking around at various web sites, such as this one, I settled on a 41 foot or 12.5m wire length. This is more than 1/4 wave length on all these bands, and around 5/8th wave length on 20. Should be a good “Aussie allrounder” but performing best on 20.

I bought some cheap speaker wire from a hardware store for construction and separated the two wires, but keeping the insulation. I stripped back some insulation at one end and doubled back to crimp a BNC pin. I then made two lengths of wire from the spare speaker wire for a counterpoise. One is 1/4 wave length for 20, the other quarter wave length for 30. 40 misses out, but at least both the counterpoises are 1/8th wave length or longer for that band. I crimped one exposed end of each of these to the shield on the BNC connector.

To give some mechanical security to the BNC connector, I taped about 7 or so cm of the three wires together, starting at the crimp. At least at this early stage, it seems to work well. We’ll see how it goes in the field.

The idea with this antenna is that there is no feedline. The antenna begins at the BNC connector – it is literally being fed right out the radio. The other end of the wire could be put up a tree and/or having the other end or middle of the wire on the squid pole. The counterpoise wires go on the ground.

"Random wire" BNC connector with 12.5m wire and 20/30 counterpoise

“Random wire” BNC connector

Mounting the wire on the squid pole

For the squid pole, I cut a small wood mount piece with a 1.5mm hole for a wire to use to wind the antenna wire around. I drilled a 3.5mm hole to mount the piece on the squid pole. This ends up about half way on the second highest segment. The top segment would be too weak for this kind of work, I think even only the bottom half of the top segment would be strong enough even for a vertical only wire.

It sits on quite nicely.

Wire mounting on lightweight squid pole

Wire mounting on lightweight squid pole

The wood mount is quite small:

Size of wood mount compared to my hand: it is about a finger width

Size of wood mount compared to my hand

The piece is small enough to be packed up in the squid pole case cap. The squid pole itself is small enough to go inside most larger packs, and even 40l hybrid type packs.

A basic test suggests that the squid pole will be able to keep the wire up in the field. We’ll see. If need be, I just need to make the hole a little bigger and it will mount a little lower on the pole.

Testing with the KX1

My initial test was at home. My house is two story, but the upper story can look down on the lower story. I draped the wire from upstairs to down, with the two counter poises on the floor upstairs. Not the best setup, and looking forward to trying it in the field.

The KX1 was able to tune the antenna on all bands, although the result was emergency use only marginal on 80. SWRs were 1 to 1.1 on 40 and 20 and around 1.5 on 30. The KX1 also shows realised power from the tune – which is quite interesting. The 20 match was showing full power (about 4 watts), with the 30 match around 2.8 watts and the 40 match about 2 watts.

I would expect better results in the field when this antenna is setup properly, with the random wire fully extended and the counterpoises at a greater distance from the wire and fully extended on the ground themselves. We’ll see, but none-the-less, early results look promising.

The whole system weighs less than 1kg, including the squid pole. It is my most light weight setup yet. If not for the squid pole, it could even get close to the station you can carry around in a pocket (or two).

I’m keen to give this a go on a SOTA summit or two over the next few weeks. Perhaps the FT-817 and the bigger squid pole and end-fed will come along as a safety net to make sure if this falls over, I’ll still be able to activate.

73 de Wayne VK3WAM

POSTSCRIPT: First activation with this setup can be read here.


One comment on “Preparing the KX1 for SOTA battle

  1. […] job. It does bend over a little, but it has sufficient strength, using the mounting technique that I talked about in this post to bear the end fed in an inverted V configuration. The activation went […]

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