Minibeams

After researching minibeams (and mini-verticals) for several years now, the laws of physics still prevail. We have both built and tested minibeams and the 60% rule seems absolute; It seems TRANSMIT antennas can be reduced in size to 60% without any significant adverse effects. Going further than 60% means extremely heavy loading (= coil heating losses) or ridiculous amounts of capacity hat wires and spokes (= inductive cancellation losses). The 60% rule therefore gives us a minimum element length of 22 feet or thereabouts on 20 metres. We have built experimental designs (on 10ft booms for 20m) and going for less than 22 ft on 20m rapidly reduces performance.

Our conclusion - supported by customer feedback - is that the "miracle" beams, with 5ft booms and 9ft long elements are doomed to fail as TRANSMIT antennas on the HF bands. Although signals go up and down when these antennas are rotated. this does NOT mean they have any gain, or very little (see Cushcraft's MA5B information - 20m gain = 3.6 dBi (less than 2.0 dBd) - with 2:1 VSWR only 90 KHz). Furthermore, very small elements, very short booms, and very heavy loading (including quad loop fancy add-ons bits etc)  means that VSWR bandwidth is very narrow. The good miracle beams have VSWR 2:1 limits of perhaps 150 KHz on 20 metres (which at least proves there is a tuned circuit at work). The bad miracle beams have a very broad VSWR curve - just like a dummy load !

There is an old Yorkshire saying "Owt for nowt". For our non-UK WebPage readers this translates as "you don't get anything for nothing" Nowhere is this more true than in the area of minibeam design !

So - here are the minibeams we sell. You will note that the 60% rule is not broken. If you absolutely can't get one of these up at your QTH, go for a good vertical or a simple single element delta loop.  If turning circle is an issue and you can erect a beam with a vertical as well as horizontal profile, check out the Quad Antenna. But please DON'T buy a miracle beam if you want reasonable results.

Note - One of our competitors has stated in their expensive glossy catalogue that we are BIASED in saying that only the minibeams WE sell work. Well, if they had carefully read what we said above, they would have noticed that we did not actually say that. What we said is that miniaturisation works down to about 60% of full size. After that transmit gain and bandwidth are difficult to achieve. We cannot therefore, and do not, claim that "only the antennas we sell work". Moral = check your facts before firing from the hip. As far as BIAS is concerned, yes we admit we are horrifically, enthusiastically, and totally biased. We will stick to our principle that we only sell things we believe work effectively. That's why you see we do not stock certain brands of amplifiers, or antennas. We could make money selling them (after all it's just another thing out of a box), but that is NOT the way that Vine Antennas services its customers. We are also aware that our minibeams aren't the cheapest one can buy. But there is a reason for this. You get what you pay for.

Force 12 C-3SS Minibeam

The C-3SS was designed by Force 12 antennas after we asked Force 12 to design something that would work well for the UK amateur with the usual space restrictions etc. Tom came up with a very simple idea. A nest of three 2-element monoband yagis on the same boom, with the 20m elements reduced in size by capacity wire loading to 24.5 ft long. The driver element cell is fed at the 20m element and energy couples (entirely efficiently) into the adjacent 15 and 10m driven elements. This match system gives a VSWR of less than 2:1 over all of 20 and 15 m and over 1400 KHz of 10 m. In addition to this, by virtue of having no traps, this antenna works with some pattern and gain on 17 and 12 m, but has to be fed through a tuner because the VSWR on those bands is over 3:1. Although this is a 6 element yagi, many users have remarked that it is less  visually intrusive than a 3 el trap tribander because of the slim elements and absence of "lumpy" traps.The claimed gain of around 4 dB - compared with a full-size dipole at the same height) on 20-15-10 is realistic. Of course we can always add 6 dB of "ground gain" if the advertising department prevails !

User comments are that this antenna, although only a 2el yagi, has the same or better gain performance than small trap tribanders such as the A-3S and TH3, but has the added advantage of coverage on 12 and 17m with useful gain and front-to-back ratio.

Manufacturers Specifications C-3SS

Watch those gain figuires! Are they within a very narrow frequency band, or over the band? Are other manufacturers telling the truth, or are they exaggerating their gain figures to sell their antennas?

We think that the Force12 claims are realistic!

Price £579 including UK VAT. Export pricing may differ. Freight extra.

Check also the Optibeam OB6-3M minibeam. Click here!