A few months ago I bought one of the DX Commander 32ft HF vertical antenna kits sold by Callum McCormick (callsign M0MCX). The DX Commander is a a six element portable vertical antenna covering the 40/30/20/17/15/12/10/6 metre amateur radio bands. I’ve been using the DX Commander with my ICOM 746 for a while now and wanted to write about how I had been getting on with it. I’m loathed to call this a review though, as this is my first DIY antenna build and I’ve only been a foundation licence holder for less than a year.
The DX Commander is 32ft vertical antenna similar to a DIY fishing pole vertical. It’s sold as a kit with several versions available, from just the pole, through to what Callum calls a ‘premium’ pack with all the required wire and fixtures. What really sets this antenna apart from a basic ‘fishing pole’ setup is the machined metal and plastic plates which attach to various sections of the pole. These provide a neat solution for connecting and positioning the antenna wires. I’ve been on the lookout for a multi band portable HF antenna for a while and this seemed to meet my requirements nicely.
When I purchased my premium DX Commander kit I paid £129, but the price appears to have since increased to £149. I also bought a set of heavy duty metal stakes for the guy ropes that Callum sells separately through eBay. The kits are available from Callum either through eBay or direct from M0MCX’s personal website. Previously it was cheaper to purchase direct through the M0MCX website rather than eBay, but now the prices appear to be almost the same.
Important note: My DX Commander is the “pre October 2017” version, after which a number of improvements in the design were made addressing all of the downsides mentioned later (and may explain the above price difference).
I ordered my DX Commander kit directly from the M0MCX website. The checkout process on the website was easy and the antenna arrived in the post within a few days as promised. There was a nominal fee for delivery, but this was understandable due to the large size of the parcel.
The photo above shows unboxing everything that was delivered from M0MCX for the ‘premium’ version of the DX Commander kit (except the pole). In addition to the plates and antenna wire, the kit includes various fixtures and fittings – hose clamps, rubber tubing, rope, bungee cord, nuts, bolts, carabiners, etc. – that are required to complete the assembly.
The DX Commander is effectively a fan dipole antenna, with a number of different length wire elements connected to a common driven plate at the base of the pole. Each of the six elements use a spade connector on the lower end to connect to screw terminals on the driven plate, which is in turn connected to the SO239 feeder connector. Depending on the input load, the antenna will ‘self-select’ the correct wire to radiate efficiently with quarter-wave performance. With the exception of the 6m band, the antenna is designed to achieve a low SWR level across all of the available bands and is intended to be used without an ATU. Everything is held up by a telescopic pole which collapses down in to something that would protrude only a small amount from a large rucksack.
The antenna comes as a kit intended to be built by hobbyists but it can also be purchased in ready to use form. The kit includes sufficient army-surplus ‘D10’ communications wire, consisting of four strands of tinned copper and three strands of galvanised steel wire. This strong yet lightweight wire is used to make the driven elements in addition to a number of ground radials.
Two spreader plates made from UHMWPE (a special type of nylon plastic) sit on the pole to keep the radiating elements apart and in position. Varying lengths of shock cord suspended from the upper spreader keeps each element under a light tension. The antenna is kept upright by three guy ropes attached to the lower nylon spreader.
These machined aluminium pieces are what really set this kit apart from a simple homebrew vertical antenna. The driven plate and radial plate attach to the bottom of the support pole.
A number of radials connect to screw terminals on the ground plate. The DX Commander instructions go in to some detail on the recommended number and length of radial wires that should be used. Enough D10 wire is included to make a sufficient number of radials. Callum references this interesting research paper on the effects of adding more radials which was an interesting read and helped me to decide how many radials to use.
The DX Commander YouTube channel has some good videos explaining how the antenna is designed and assembled in more detail.
When I built my DX Commander there were two sets of instructions available for download from the M0MCX website. The second document was an addendum/addon to the first. I actually found following the instructions a bit tricky, having to cross reference between the two (sometimes conflicting) documents. As a new amateur radio hobbyist who had never built an antenna before, I found the ‘high level’ instructions lacking at times, glossing over various details between the steps. I did mention these issues to Callum at the time and I’m pleased to see he has since reworked the instructions in to a more coherent and comprehensive single document. The latest version of the instructions can be seen here.
The first time assembly process mainly centres around preparing the various lengths of wire for the radials and elements. The instructions suggest planning a full day for the initial build. I was initially sceptical that it would take all day to prepare an antenna that was designed to go up in 20-30 minutes, but the instructions did turn out to be correct. Callum has some helpful YouTube videos on assembling the DX Commander which I watched before the build day. His hints and tips video was very useful.
The kit includes a number of hose clamps of varying sizes, intended to sit at the join between each section of the telescopic pole. Rubber tubing must be trimmed and fitted to each clamp, to improve grip on the pole, as they are used to prevent the pole collapsing. I used a permanent marker to number each clamp to accelerate the assembly process. I’ve found in calm weather these aren’t strictly required so can be omitted if just throwing up the system for a quick bit of single band operating.
Next I prepared the metal base plates by fitting screws in to the predrilled holes. Wing nuts are used to retain the various wires which will have spade connectors fitted later. I found I had to countersink all of the threaded holes to get the screws to sit flush against the metal plates.
There were some manufacturing residues and sharp edges on the metal pieces, so I gave them a good scrub with a ‘Brillo’ pad (steel wool) and they came up great. I have added my own colour coded labelling to the plates and element wires to help speed up the putting up of the antenna.
After trimming the various element wires from the supplied coil of D10 wire, I used the remainder to create a number of ground radial wires. I think I ended up making 20x four metre radial wires. To make it easier to store the radial wires, and quicker to assemble the antenna, I bunched the radials in to groups of five which were then soldered in to a single spade connector. There is a generous number of screw terminals on the radial plate so adding more in the future will be easy if required. Working with 100 metres of steel wire was a bit awkward at times and needed a lot of space to untangle and measure to length.
At this point the antenna pole needs to be assembled so that the various lengths of rope and bungee cord can be measured, cut and tied in place. I found assembling the antenna in a horizontal position supported by two garden chairs worked quite well.
The base plates provide a tidy way to assemble the elements and radials around the pole. Spade connectors are supplied in the kit for attaching to the ends of the radial and element wires. The connectors can just be crimped on but for maximum durability I also soldered mine. The wing nut which connects the SO239 centre conductor to the radiating plate fouls on the adjacent nuts - I may grind down the edges of this wing nut or replace it with a standard nyloc nut.
The lower spreader plate is a lot thicker than the upper spreader plate, giving it the rigidity needed to support the pole and guy ropes. Each of the six antenna elements go through holes in the spreaders, which line up with the respective screw terminals at the base of the antenna. The hose clamps sitting above the spreader plates serve the secondary function of keeping them in position (the underside butts up against the edge of the larger pole section underneath it).
With the exception of the longer 30m and 40m elements, the wires are suspended from the upper spreader plate using elastic shock cord. The upper spreader is made from thin plastic and bends a lot under tension from the elastic shock cord (in the newer version of the antenna the upper spreader is now made from thicker plastic which is a definite improvement). The 30m element hangs from some shock cord looped over one of the highest hose clamps, while the 40m element loops over the top of the pole and comes a few feet back down. The 40m element is kept in place using a small section of rubber tubing placed over the end of the pole.
Once the antenna is secured to the ground using the three guy ropes, the feeder cable can be connected to the SO239 socket and the antenna is ready for tuning/usage. I’m using a ten metre RG-213 coaxial feeder with soldered PL259 connectors and a selection of Fair-Rite clamp-on ferrite chokes just for good measure.
The instructions provide the precise lengths which the six elements should be cut to. Even though I double checked the measurements for my element wires before trimming them, I found the initial SWR readings to be somewhat mixed. Next time I’m building an antenna I won’t repeat the mistake of cutting element wires right down before taking any SWR measurements.
Tuning a multi-band antenna is more complicated than tuning a single-band one. Changes to one of the wire lengths will have some interaction on the SWR levels of other bands.
I’m glad I had an SWR meter to hand for this antenna build, as just relying on the lengths given in the instructions wouldn’t have been sufficient (in my case at least!). In my first attempt the 40m element was almost perfectly tuned, but as will be seen below some of the other elements were not as successful.
I used my SWR meter to plot each of the six elements in the charts above. The 15m and 6m bands are shown with dotted lines because there are no physical elements for these bands, they are ‘bonus’ frequencies which should also be resonant when everything is set up correctly.
The charts above show that the 40m and 30m elements are a good length and working well. The 20m and 17m elements are not bad but might benefit from being lengthened just slightly to move their SWR curves down a little. The 12m and 10m elements are quite far off their targets and both need to be shortened in length to shift the SWR curve up in to their respective operating frequencies. The 15m and 6m bands are a bit hit and miss too, but these should be corrected by making the aforementioned adjustments. The instructions do mention an ATU is required when using the 6 metre band. I suppose each installation is going to be slightly different, and getting a multi-band vertical to be perfectly repeatable when the customer is cutting their own element wires is virtually impossible.
For the second outing of my DX Commander, I borrowed an SWR meter with a graphic display, which made life much easier and I was able to fine tune each of the antenna wires to improve the tuning on all of the bands.
My early experiences operating with the DX Commander so far have been positive. There were poor band conditions on the day I was building and testing the antenna, but my first contact didn’t take long to come through, an SSB QSO (10 watts) to south east Europe, which was an encouraging start. I’ve since had some good successes operating data modes at 10 watts or less, including spotting and being spotted in Canada and Australia using the WSPR mode at 1 watt. I’m looking forward to operating SSB at 50 watts with the DX Commander once I have passed my RSGB intermediate licence exam. M0MCX has some sample recordings on his website demonstrating the antenna being used.
Over the last few weeks I’ve become more proficient at putting up and taking down the DX Commander antenna. I can go from packed away in bags to ready to operate in about 25 minutes which I think is quite reasonable. Taking it down is much quicker and barely takes ten minutes to pull apart and pack away. I have bought a few accessories to make storage and assembly a bit easier. Two heavy duty tent peg bags from eBay are used to contain the antenna’s parts when not in use. I use one bag for the ground pegs, guy ropes, a rubber mallet and screwdriver (for the hose clips), with the other bag used for the four plates and the antenna wires. Some cheap aluminium carabiners and self-tightening tent guy ropes further simplify the process of putting up the DX Commander.
Having perfected the tuning of the antenna and spending some time operating with it, I’m very pleased with the DX Commander. For the £129 I paid, I thought it was good value and good quality. Obviously it’s more expensive than a homebrew vertical antenna, but this feels like a well thought out product which makes the whole process of building a portable HF vertical antenna easier. It’s clear that Callum has put a lot of time in to this project and is continuing to evolve and improve it over time.
In building and tweaking the DX Commander I’ve progressed my understanding as an amateur radio operator and learned more about antennas. Assembling one of these again would be much faster the second time around and it’s good to see the instructions have been reworked since I built my DX Commander.
If you are looking for a sensibly priced portable HF vertical antenna, I definitely recommend putting the DX Commander on your short-list. Callum’s great after sales customer support and the ‘lifetime discount replacement pole’ option further add to the overall value of the DX Commander. A fully prepared version of the DX Commander is available for £289 from the M0MCX web shop if you can’t spare the day needed to complete the final assembly of the kit.
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