So, today marked the commissioning of my first purpose-built HF vertical antenna, a “squid pole” (that’s a collapsible fibreglass fishing pole) based antenna that takes the general idea of a fan dipole and stands it all up vertically, with radials exiting the base spread along the ground.
I headed to a local park with another member of my local radio club, who in this article I’ll call J. J was an absolute blast to hang out with, and brought along a 30Ah LiFePo4 battery and his iCom 7300 shack rig, along with a QRP-Labs QCX-mini CW transceiver for 40 metres, and a whole heck of a lot of coax which turned out to be SUPER useful as the feedline I’d brought was a miserly 3 metres long. We parked ourselves on a convenient picnic table about 15 metres from the antenna base and proceeded to get things rolling. Our main goal was to tune the antenna, then do an initial evaluation of its performance with whatever time we had, and we thought we might get a POTA activation in there at some point too, but, well, read on!
The antenna is made by M0MCX of England, and is called a “DX Commander”. There are a few versions of this antenna, mostly differing in pole length or number of sections and thus in which bands optimally fit. Mine is the “Rapide” version which can host up to 6 different bands and I have elements cut for a nearly perfect tune on 10m, 12m, 15m, 17m, 20m, 30m, and 40m. I can theoretically run any combination of 6 of these at a time.
There’s the antenna set up at the park just outside the outfield of a baseball diamond. The photograph is pointing roughly north-ish. In this photo, I’ve fitted the 40m inverted-L element from the tip of the mast (it comes down via a guy to the ground, and bends the tip of the antenna slightly off to that side), replacing the 30m antenna (which folds back straight down from the tip and leaves the antenna standing perfectly vertical).
Now, the 40m antenna changes the tune of the other antennas slightly compared to when the 30m is fitted. I didn’t measure the exact differences today, but I did tune the complete set for as good a match as possible with the 30m element installed, since that’s how I intend to run the antenna in most cases (I prefer daytime operation and daytime 40m isn’t so interesting, I’d rather have the 30m band). So basically if I’m going to run 40m I am most likely specifically there for using 40 so perfect tune on the other elements wasn’t a priority in that case.
Setting up the antenna for the first time was pretty straightforward, and I did it easily, completely unassisted while waiting for J to arrive. I’d already “built” it (e.g. cut the elements and radials, put on the fork connectors, done all the heatshrink and measured out the bungee cord clips to hold everything in place, set up the ground plate and the distribution plate, etc etc) at home, laying horizontally. Re-doing that in the field was thus a repeat without all the fiddling. But there are definitely a lot of things I could consider doing to make it go a lot faster next time, which I’ll get into towards the end here.
Basically, you use the base of the extensible pole (the first segment) to mark out the zone for the three guy lines, which get staked into the ground. I forgot a hammer and the ground was rather hard to work with, so I dented up the bottom of my stainless steel water bottle (which was full) bashing them pretty far into the ground. It worked well enough, but the poor water bottle probably dislikes me now. It still stands up straight though.
Once the guys are ready, you extend the pole out horizontally and add the rigging bits and elements. Here is where you have two options - as the pole gets longer, you can slide the spreaders (that’s those little bits of white plastic which separate the elements and provide attachments for the guy lines) onto the pole one at a time as you go, OR you can just get all the sections out and friction-locked into place and then slide the spreaders on in a single pass. I opted for the former this time, but I think next time I’ll opt for the latter. We’ll see which goes faster.
In addition to the friction of the pole holding everything up (against six element’s worth of bungee cords trying to collapse it!), I added a trick stolen from the larger versions of this pole: hose clamps covered in clear aquarium plastic tubing. They go around the smaller section just above the joint to the larger section below it, providing a safety in case the friction in the joint isn’t sufficient to keep the antenna lofted. They’ll hold it up all on their own, if necessary. Adding these requires an extra tool or two in the kit bag (they have three different sizes of hexagonal head, two metric and one English, all from the same brand in the same store!), but adds a level of safety I won’t forego except for perhaps a SOTA expedition where I’m pretty sure the only people around will be me and any fellow ops who will be appraised of the possibility of a pole collapse. Granted, the worst thing that can happen if the pole collapses is that a smaller section of pole falls below a larger one and they get shredded onto each other due to misalignment - the assembly won’t fall sideways or anything like that due to the guying arrangement - but it’s an easily preventable risk for the cost of a few extra oz and three minutes extra setup / teardown time.
Speaking of setup/teardown time, I didn’t time myself since this was my first real deployment, but I’d say that other than the issues beating the stakes into the ground, setup took about 20 minutes and teardown took about 15, working at a slow and thoughtful pace and coiling my wires carefully, etc. As I get more proficient and learn how to pack the wires for more rapid deployment, I could easily cut both times in half, and maybe down to a third if I cared enough to really practice and fine tune it. Given that it’s already “not a big deal”, I don’t see myself trying to hit some arbitrary number.
Once the spreaders and safety clamps are in place, the elements clamp to the transmitting plate via fork connectors and wingnuts, thread through the holes in the spreaders and ultimately have a little loop in their top end clipped to a bungee cord hanging from the next spreader up. The 30m element loops through a ring at the top of the pole and comes back down in a manner akin to a folded dipole and clips downwards to the top spreader plate, and as mentioned previously the 40m element comes straight off the top and is made into an inverted-L with its own guy line.
We used a variety of antenna analyzers, all of which largely agreed: two NanoVNAs (a v2 and an H-4) and an FA-VA5 which had previously been calibrated against a laboratory grade SOL (short, open, load) test set. The FA-VA5 is what I’ll likely haul around with me in the field, but it’s a little fiddly to operate and I need to get more used to it, so we ended up reaching for the NanoVNAs for the most part. They’re still more accurate and far more useful than the built-in SWR meter on a shack radio.
The tuning on this thing is pretty good. I mostly erred - when I did err - on putting the resonance slightly low in the band as I intend to do QRP CW with some radios that don’t have ATUs installed. In most cases the best SWR was around 1.1:1. I forgot to write down each band’s exact tuning but in nearly all cases the worst case at the extreme band-edge was 1.5:1 or better and in no case did it exceed 2.0:1. So, that’s an exceptionally good tune across a wide range of bands. Could I do better? Sure! More (than the 16 it already has) radials and longer radials might help a bit. I could trim the elements slightly more perfectly to geometrically centre the resonance within the band so that I get the lowest SWR on each band edge, but it’s well within “pretty darn good” for a field antenna and the surrounding trees, soil moisture, etc. will all have an effect on the tune as well. So, basically I’m quite happy with the tune and will only put in the effort to improve it that last little bit if I find reason to suggest that it really needs it.
After we had the tuning verified, we fired up the iCom 7300 to see what was out there. Since we were operating from the middle of an extremely dense urban environment we expected mostly QRN and QRM to dominate, but we were pleasantly surprised with an unusually quiet background on nearly all bands. We started on 20m since we figured in daytime that was our best bet for a contact, and right off the bat we heard, loud and clear, the well-known S51DX in Slovenia. I asked J, “do you think he can hear us?” and J flipped the set to 100W and right off the bat raised S51DX on 20m for a two-way signal report of 599. Not too shabby for a first contact on a new antenna, on 20m, in daytime, in the middle of dense urbanity! It also proved my general theory that in terms of QRO, 100W is absolutely plenty of power. You only need more if you’re trying to punch through some really nasty conditions or using a less efficient antenna.
So, J handed me the mic and I also contacted S51DX, making my first HF contact ever a solid NA-EU DX on my very own kit antenna. A good start, and we thought we might claim a nice unused section of the 20m band and start working a POTA activation. Fortunately for us, J decided to double-check the POTA reference and we realized that the park we were in had a duplicate name as another park entry quite a long way away from our actual location and I had mistakenly copied that park’s reference! Regrettably, the park we were actually in did NOT have a POTA number, likely because it was a city park and not belonging to a larger governmental body. So that put the kibosh on our POTA plans for the day. Nevertheless, the clear and moderate summer weather had us wishing for a little more, so we held out to see what else was active on other bands.
We had a few touchy contacts on 30m then replaced that element with the 40m since I wanted to tune that and hadn’t yet. After we got that in place, we spent the rest of the afternoon pottering about with CW, reaching a few hundred km away on 40m QRP (~4.5W) in broad daylight and being quite pleased with the overall reception quality we were getting.
As an ensemble, the complete antenna in field trim weighs less than 3kg complete with radial and element wires and guying, and is easily backpack-able (if you strap the pole vertically to the outside). It’s an ideal rig for a longer-term SOTA or POTA trip that could benefit from more than a random wire; a field day; or - as we did - futzing about in a park or on tour somewhere. It’s not a yagi up a 60m tower, but for a 1/4𝛌 vertical at ground height, it does exactly what it says on the tin: tunes up beautifully, has a sufficiently wide bandwidth on each band for good SWR right out to the band edges, deploys and packs up quickly enough to not be a major drag on operations (unless you’re doing a run-and-gun SOTA, perhaps), and weighs little enough that I’d have no second thoughts whatsoever about bringing it along on modest hikes or even a bike DXpedition. It’s a perfect little base camp antenna too.
My only concern with it is that the base of the pole didn’t have a ground spike - while there’s considerable downforce from the guy lines helping to keep it in place, I was pretty easily able to adjust the angle of the setup by sliding the base around. I would ideally prefer at least a 2-3" spike in the end cup to prevent that. I may just pick up one of those chromed leather collar studs from a local punk shop and drill a hole in the end cap of the bottom tube to mount it.
So the short list of things to tweak:
- A better guying arrangement for the 40m element, featuring a longer guy line and perhaps a way to quickly rig it on the outside so I can do it with the 30m element in place.
- A ground spike to keep the bottom stable in the event of high winds.
- The 30m element got shortened a bit in the tuning process and I need to make up a little bit of rope to connect it to the now-too-short bungee segment that holds it taut.
- I’ll probably make a wire winder frame to permit me to rapidly coil all six main elements together and deploy them more or less simultaneously, speeding up the setup and teardown, and I may do the same for the radial sets.
- A small stuff sack to hold the various bits and bobs, plus a dedicated set of sockets for the hose clamps.
- A 10-15m feedline with a BNC connector on the radio end so I can forego an adapter.
Considering the usefulness, simplicity, and utter hackability of this clever antenna platform: am I a happy customer? You bet. I’ll probably end up buying at least one of the other variants of this design before too long, too.