I always fancied a low-angle vertical for 10m band and after doing my research, came across the Solarcon Imax 2000. It was a toss up between this, a Sigma 4 copy or the Sirio 827. The Sigma 4 is now called the Sirio Vector 4000 and I discounted this one because of the size of the radials which seemed excessive for my plot , Same with the Sirio Vector 4000 which is just too tall. Even so, the Sirio Imax 2000 is still 24 feet in length. But read on, it’s actually fairly stealthy for such a tall antenna.
I bought Sirio Imax 2000 from Nevada and it came in a box a couple of days later. Be aware, the box is just over 8 feet long since the antenna is built in three sections. The first two are relatively substantial and the third section is extremely lightweight – although no doubt strong since it feels solid fibreglass (with the copper wire running up the inside).
This is made for the American market and the first thing you’ll notice is that the U bolts – supplied and pre-drilled holes are aimed at a 1.5 inch pole (38mm). I prefer 2 inches and had in mind putting mine on top of a 2 inch steel scaffold tube. I therefore bought a 40mm steel tube, slotted that inside the scaffold tube and widened the holes slightly to accommodate U bolts of 42mm. I’m not a professional engineer so my hole widening was slightly “Heath-Robinson”, however I was fairly comfortable with the result.
The base of the antenna is an extruded aluminium section that houses the SO239, the coil and various innards of the antenna and has this integral clamping arrangement. I was quite impressed actually. The factory use a very high-grade glue that perfectly oozes out to weatherproof everything.
The lower section connects to the middle section with a plated screw assembly which I tightened by hand and finally the top section has the same arrangement but in a much smaller design since the top piece is about as thin as a pencil and certainly will waggle around in the wind, although I’m sure with no ill-effects.
The two aluminium “wheels” screw up and down which changes the inductance of the coil. As per factory, it seems to come tuned around 27.5Mhz (according to the MFJ analyser) when only 8 feet off the ground. It’s apparent that as you raise this antenna fully, the resonant frequency will rise – as will most antennas to a point. I screwed the wheels right to the top so that I could achieve 28Mhz right through 29.6Mhz however, I have lost the benefit of using this on 15m. If you leave the antenna aimed at around 27.5Mhz, the antenna will behave rather nicely as a half-wave monopole at 21Mhz with SWR of less than 2:1. Changing the resonance up towards 28 (and actually it ended up at around 28.7), my 15m band has gone out of adjustment, just over 3:1 SWR.
Bandwidth is huge, from 21.9 through to 30Mhz, the SWR doesn’t go over 2:1. Currently, mine is tuned for 28.7Mhz but the SWR hardly moves from there down towards 25.5Mhz, where the SWR starts to rise, maybe a whisker over 2:1. Then it falls again as it starts to become a half-wave monopole with the SWR falling down to 1:1 at 23.5Mhz. Dropping the frequency further, the SWR just starts to become marginally unacceptable for 15m band. The next time I drop the antenna, I will lower the tuning rings again so that I can comfortably achieve 15m band within 2:1 SWR.
12m is also superb, still behaving like a 5/8th rather well and the SWR seems to hover just under 2:1 SWR. My amplifier copes just fine with anything under 3:1, so I’m happy.
But I really bought this antennas really for the 10m band and I tested the stick during CQWW RTTY and logged 48 contacts in an hour or so, running 400 watts of hard-duty RTTY through. I was impressed with my transmit ability, reaching all over the world, including Ascension Island and some other exotic places.
As the 10m band closed later on Sunday evening, I noticed my 60m loop was slightly better on DX reception depending on the contact and the distance. I’m not being unfair, a large loop will receive quite well although during the day, the vertical was a clear winner on receive.
I also had the interesting experience of listening down on 11m CB band too. Local stations in and around Birmingham were fully quietening on FM and I was impressed with the low angle this antenna must have.
In conclusion, if you can live with the 1.5 inch mounting bracket arrangement, I’d say this was a first-class buy. It is rare that I buy antennas, preferring to make them – but for under £100, I am genuinely impressed.
