After accidentally coming across Callum McCormick M0MCX’s YouTube videos, watching and receiving very good recommendations from radio amateurs worldwide, in my search for a vertical antenna, I started looking seriously at the DX Commander multiband antenna.
The choice for a vertical antenna was based on the space required to set up a multiband antenna, ability to hide the antenna and the radiating angle to operate DX.
Left: Typical vertical antenna’s radiating pattern
The first consideration was the shocking prices of the more traditional vertical antennas available in the market. Your choices are basically something like the Cushcraft range where a 10 to 80Meter vertical antenna like the R9 will cost you US $ 700 (R11 600.00) before shipping and delivery which is also not cheap. The Butternuts, which are traditionally a good alternative, are also very expensive. After months of searching and researching, I realized that buying a complete and effective multiband antenna at UK £195.00 ($250) before delivery is a much more reasonable decision for my pocket.
Although it is not a traditional aluminium antenna, it is much less conspicuous than the other options. Which brings me to my other consideration, which was to look for something that would satisfy my XYL and not be in the eye of the neighbours.
When you start looking at the benefits of the DX Commander, there are many that count in its favour. First, it is lightweight but sturdy. I have not had any problems in severe windstorms yet, because it simply bends with the wind and just bounces back to its original position. But let me first explain what the DX Commander is so you will understand what I mean.
The DX Commander is a “Kit” that must be assembled by you, as is the case with all the other antennas you buy. The “Kit” should not deter anyone, it is just as easy as other antennas to put together, if not easier.
The DX Commander is a 7 band (10 to 40Meter) vertical antenna. You can order an optional 80-Meter fitting and wire that is mounted in an inverted L formation. It works very well. There are no shortcuts or coils for any band, so there is a minimum of 300 Khz usable bandwidth per band available.
The base of the antenna is a 9.5 m telescopic fiberglass pole. You put a radial plate at the bottom of the pole to which you attach the radials, which should preferably be laid 360 degrees around the pole for best results. You cut about 36 wires of about 3.5 m each to make up the radials (a good rule of thumb is that the total length of the radials should be 2 x wavelength of selected band. At 4 x the wavelength, there is no longer any significant benefit.
The kit comes with enough wire for the radials and the elements for the antenna. It also comes with all the screws and everything you need to put the whole thing together. The wire is suitable for elements that can use with up to 1500-Watt of RF power.
The package comes with the following items:
1. DX Commander 9.5 m Pole
2. Ground Plate 3 mm aluminium
3. Radiating Plate 3 mm aluminium
4. Guy Plate – 8 mm UHMWPE plastic.
5. Mid-Spreader UHMWPE
6. Upper Spreader Plate – 5 mm UHMWPE
7. Upper Double-Eye – 5 mm UHMWPE
8. SO239 Assembly with flying lead
9. Appropriate number stainless bolts
10. Appropriate number stainless wing Nuts
11. Plenty of Fork Connectors (earth)
Plenty of Fork Connectors (elements)
13. Hose Clamps (XL, L, M & S)
14. Approx. 90 cm 10 mm ID tubing
15. Small Section of 6 mm & 12 mm tubing
16. Length 4 mm elastic shock cord
17. Paracord for guys & element extensions
18. 12 Plastic Carabiners that snap together
19. 15 cm of glue lined shrink-wrap
20. 100 m DX10 Mil-Spec wire (You can ask for extra 50 m wire if you also want to set up the 80m.)
As already mentioned, the radials are all 3.5 meters long, but I added North, South, West and East another 5m length each to help with the 80m element, although that is not necessary.
The elements of the different bands look like this:
• 10m – 2.45m + 5 cm fold back
• 12m – 2.78 m + 6 cm fold back
• 17m – 3.83 m + 6 cm fold back
• 20m – 4.82 m + 20 cm (longer cover compensates for slightly shortened element)
(OPTIONAL: 20 m – 4.88 m + 6 cm – if it fits, depends on the version of the pole)
• 30m – 6.74 m + 6 cm
• 40m – 11.15am (fold back down on the pole which also gives you physical 5/8 for 15m) See the explanation later on this.
• 80m (OPTIONAL) and replace 30m element) 19.5 m wire (go to where your 30 m would have been (approximately 6.7 m high) and then throw the remaining element over the nearest tree or through a window, using a paracord extension.
USE OF 40m ELEMENT ON 15m BAND
According to the books, dipoles and verticals resonate on every equal (second) harmonic. This means that our element must therefore resonate from 7.11 MHz to 21.3 MHz as well. If it were that simple, we would not even talk about it further.
In practice, however, the third harmonic is much higher and we really do not know why. Even the software modelling places the resonant third harmonic frequency for a tuned 7.1 MHz vertical at 21.6 MHz. It’s too high.
The easy way out of this dilemma is just to make a longer element for the 40m band. A longer element, by adding another 10 Creative Minds, would still tune the whole 40 m band well and get a perfect mood at 21.25 MHz. And that’s what Callum did before. However, it irritated him that the wire was slightly longer than the pole itself and that the top of the element was floating around in the air. Of course, it did not look good. His self-proclaimed OCD at work…
Coincidentally, Callum then had to cut a new set of elements as part of compiling an updated user manual to achieve very accurate element lengths and to determine what impact (if any) the amount of folding back had on the tuning of the band.
Callum then cut a random element length, slightly too long for 40 m (actually 11.06 m) and folded, the extra amount of wire for this long element, back down the upper part of the DX Commander pole. He was convinced it would be too long and a futile exercise.
It seems, however, that he achieved a perfect tune for 40 m, but this ‘top load’ meant that he also found a perfect match for 15 m band. Actually, the tuning ends up at less than 21.1 MHz. You can cut the fold shorter and move the 15 m up if you like. It’s starting to act like a 5 / 8th wave now.
Both 40 m and 15 m benefit from this long turnaround but to a different degree. 40m see this flip probably scarcely because you can cut the flipped part shorter and almost nothing will happen to the tune.
At 15 m, this flip over or fold looks like a happy accident. Although the bandwidth of 2: 1 is still more than 400 Khz, it gives the diligent operator the ability to tune the element to the portion of the band you have the lowest SWR (CW, Digital or SSB). The shortening of this element therefore has almost no effect on the band tuning of 40 m.
The added benefit is that the physical length of this 15m element becomes close to the 5 / 8th wave.
You can also, with a small adjustment, by exchanging the 30-meter element, put on an 80-meter inverted L that works great.
To sum up, the DX Commander is a very good solution for someone who wants to easily and relatively cheaply install a very useful antenna that can also be used very easily if you want to store it quickly and at a club event or in the field.
I attest to excellent service and excellent performance of the antenna. I accidentally broke the top of the pole one day with stupidity and undue force and Callum replaced it for me with a brand-new pole for free. That’s what I call service.
Take a look at https://www.m0mcx.co.uk/ and laugh at all Callum’s antics on his videos on YouTube: https://www.youtube.com/user/m0mcx
Greetings and 73 from Marius Lubbe ZS1ML
Technical editing by Jan Van der Vyver ZS1VDV