Mosley Minibeam in practice: experiences and comparison with other antennas

Mosley Minibeam in test: Hot or junk?

The headline "Hot or Junk" of the report may sound a bit dramatic, but based on a well-known TV show, I would like to point out the "practical" added or reduced value of a minibeam compared to existing space-saving vertical or wire antennas.

To understand the reason for the comparison, I need to elaborate a bit. Since 1991, I have been operating shortwave almost exclusively with a wide variety of antennas. "Most different" in my case meant bigger and better each time. From Quads to LogCell Yagis, even bigger QUADS, interlaced multi-band Yagis, to finally motorised Stepper Yagi. So I was spoiled by DX successes and my dream to work all DXCC countries was also fulfilled in 2015.

I myself would not have thought it possible at the time after over 35 years of amateur radio, but all of a sudden the air was out and interest in amateur radio ebbed to "zero". Five years passed and by chance I met a fellow OV who reawakened my interest in AFU operation.

But now the problem. All antennas had been dismantled and the roof of the house restored to its original state. Likewise, there was no station left. The "antennae on the roof agreement" with my wife had also come to an end.

So I was faced with completely new challenges. Where in the past size and height hardly played a role, now limits were set in the form of inconspicuousness, wind load, weight, garage roof installation (max. 3.5m turning radius) and quick dismantling possibility.

And with these conditions, the best possible should now be achieved!

Mosley Minibeam: A compact and lightweight antenna solution

The idea and the first tests

The next step was to build a trap-dipole for 10-15-20 in horizontal position, and an inverted-vee for 17m. Both in 10m height. These antenna systems are still in operation and will be used as a reference for comparison.

With the above dipoles, first connections were made on the higher bands and single DX stations found their way into the log. Since the setup favours the directions north and south, the possibility to work W/PY/LU/VK/ZL is quite limited.

So I developed the idea to build a small rotating antenna, which has a preferred direction, maybe even some gain in this direction and a 3.3m radius of rotation. The bands to be covered were the classic DX bands.

But the challenge was now again the restrictions of weight (only 9.5m rotating aluminium telescope mast on 3m garage available), size expansion and inconspicuousness.

The Mosley Mini-32A three-band MiniBeam

The Mosley MINI-32A is a classic three-bander. 2 elements in spotlight-reflector constellation with traps in the elements. A concept that many manufacturers have been using for years. Not the best, but not the worst either. According to the simulation of OM Fritz, DM2BLE (SK), the Mini-32A has the following characteristics in gain and V/R.

These data were quite promising, although I always question theoretical values first. After receiving the 190cm package and unpacking it, everyone will ask themselves, is the price justified for so little aluminium?

But then I remembered the song by Roberto Blanco and Grandpa's collection of quotes: "A little fun is a must..." and "There's no talking about money". After unpacking the individual parts, the simple construction pattern became apparent, even without looking at the manual. The elements, or pipe sections, are marked by coloured rings and the parts of the element fastening are actually almost self-explanatory.

You only have to remember that the coloured rings of the tubular elements have to point to the boom and the construction goes off without a hitch. Only the element length has to be taken from the manual. I would have liked to see more markings here so that I could have a rough preliminary adjustment and not have to juggle with the folding rule.

By the way, Mosley uses cast coils in the reflector and emitter for shortening. Thus the dimensions are manageable and the turning radius is just under 3.2m with a boom length of 183cm. The antenna is super light and with just under 4.5kg not heavier than a VHF Yagi. The wind load is extremely low and the material quality and accuracy of fit I would describe as decent.

You should not expect a monster beam here. The MINI-32A is a super-lightweight, which can only be achieved by thin element diameters. The manual (2015) should be revised a bit. The drawings could be replaced by contemporary photos or computer drawings.

Despite antique sketches, but all in all understandable. And for comparison, the ancient Egyptians also built the pyramids quite properly with their "papyrus manuals". As with many US manufacturers, you first have to convert the given masses into metric.

After the conversion, we started to build the pyramids. It took about 25 minutes and the antenna was ready except for the mast mount. (Ideal for portable activities and therefore fieldday compliant).

The mast mount is a point of criticism. It only allows mounting up to 35mm mast diameter. This was replaced by a mast mount up to 50mm mast diameter. According to the length specifications in the manual, the antenna was now pre-tuned. The Mini-32A was now placed on three wooden trestles on the garage roof. The standing wave ratio (SWR) on all three bands was 1:1.2 at the lower end of each band.

By the way, the coaxial cable is connected directly to the radiating element. The core of the cable must be connected to the so-called hot side of the radiator. The cold side is earthed to the boom. The manual clearly states that a 1:1 balun is not necessary or should not be used. Here you should not be irritated by Youtube videos in which users use a BU-50 balun.

In general, some Youtube videos are rampant, which even show a wrong set-up of the antenna. For example, they show a setup where the elements are isolated from the boom. The parts used actually belong to the mast mounting!

But back to my setup. The manual prefers the "coax choke", which consists of 5 turns of coax and a diameter of 16 cm. The winding method is compared in the manual to winding a garden hose. My Gardena box winds the hose nicely side by side. My hose trolley uses more of a knot-and-groove winding method. But side by side is the choice here!

Mosley Minibeam: Performance and practical experience

The first test was actually done with the antenna on wooden trestles. Due to the influence of the garage roof about 1m below, I didn't expect much. But a comparison to the Upper&Outer on 21Mhz already shows louder signals on the side of the MINI-32A. That was quite astonishing. After that, the set-up took place at a height of 8.5 m (5.5 m above the garage roof).

Now it was time to get down to the nitty gritty. The transceiver was set to 14MHz and searched for SSB signals. On 14MHz, the MINI-32A has the greatest shortening and corresponds to only about 60% of the full element length. Nevertheless, it was found that stations were louder with the beam than with wire dipole or Upper&Outer. Rotating the antenna resulted in a side attenuation of up to 3 S-stops and a V/R of about 1-2 S-stops. Unfortunately, these values varied due to unstable ConDX. However, the V/R was generally more pronounced with overseas signals than with EU signals.

I definitely did not reach the simulated 17dB! But my imprecise S-meter of the FT991 and the fading during the QSO's do not allow precise statements. Nevertheless, these values are respectable for the size of the antenna. Mind you, the MINI-32A is only 8.5m high and only 3.5m from the roof of the house.

But how does the antenna perform with overseas DX? A direct comparison with the wire dipole showed advantages in favour of the MINI-32A. The signals are basically louder compared to the dipole. Partially even several S-stages, which surprised me a lot. According to the simulation results, the MINI-32A should actually not be much better than the dipole! With the MINI-32A it was even possible to hear stations that were lost in the noise on the wire dipole. Sometimes theory is lost in practice.

Overall, the beam is much quieter than the wire dipole. I am talking about 6dB-10dB in my setup. Turning the beam away showed a V/R of about 1, maximum 2 S-stops, which somewhat dampens a QRM from the side and from the rear. A huge highlight was the CQ call from VK2CIA over the long path. A call with my dipole was unsuccessful. Then the switch to the beam. Instead of S5-S6 with dipole, VK2CIA was now received with S9 and answered my call immediately. He complied with the request for a real report and also gave me S8-S9. And all that with 100W output. I had fun to finally reach the other end of the world in SSB (Single Side Band) again.

Interesting were also further tests using the WEBSDR from PY2GN in Pardinho Brazil, C37AC in Andorra, NA5B in Washington and R8AEC near Cheyabinsk. On 20m, an attempt was made to listen back to the own signal and compare it with other DL stations. The results showed in signal strength that the MINI-32A is not a monoband, or a full-blown Yagi. Stations with SteppIR, Ultrabeam and other heavyweights were sometimes up to 2 S-stages louder. But, the volume differences were never so serious that it would not have been enough for QSO.

The most interesting test was a QSO with EA5H in Valencia. He uses a 2ele QUAD and 500W and a T2LT vertical antenna next to it. His beam was pointed towards PY and with the PY2GN WEBSDR he was able to produce a 5/4-5 signal with the T2LD vertical antenna and a 5/9 signal with the QUAD. My signal with the MINI-32A and 400W PEP was to be picked up by PY2GN with 5/7-8 in Brazil. So I had to admit defeat to his QUAD, but was superior to the T2LD! Then the bands 21MHz and 28MHz were examined more closely!

On 21MHz TO60CNES from French Guiana was calling CQ. The signal strength was about S5-S6 with the dipole and S9 with the beam. Despite the pileup I was able to reach the station and asked for a short report with switching test between the antennas. Lo and behold, with the dipole I was heard at S6-7 and with the beam at S9. Here, too, the MINI-32A works. The Upper&Outer performed poorly on 15m. Apparently it is really "multiband-incapable", although 21MHz and 7MHz are harmonious to each other. During the activity week Rheinland-Pfalz the last tests on 28MHz should now take place. How good is the antenna at signals from a greater distance using groundwave? Patrick, DH2PA, from near Landau (140km distance) was heard on 28MHz. He is operating with a 9ele 5-band Yagi at high altitude and decent power.

I could hear DH2PA well with the MINI-32A (S1-S4). With the dipole only noise! Due to the difference in power to DH2PA I was missing 6dB. Nevertheless, a QSO could be made. In the meantime, this was compensated by the purchase of a PA. In the following days a few attempts were made in FT-8 with 50W output on 21/28MHz. Here the PSK reporter is an enormous help. Once we transmitted with dipole and club callsign, once with MINI-32A and our own call. (Dipole transmission time 10min, MINI-32A 20min) The differences were significant and turned out positively in favour of the MINI-32A. On the one hand the number of receiving stations and on the other hand the received S/R reports support the advantages of the MINI-32A.

Mosley Minibeam: A low-cost and effective solution for shortwave operation

The MINI-32A has now been set up on the garage roof for some time and my enthusiasm is not waning. All restrictions have been met, I am not financially ruined, I sleep well during storms and the neighbourhood has not noticed my setup at all. What more could you want! Perhaps a little more load capacity. The Mini should not be fired with 750W continuous wave. 250W in RTTY, FT8 are the maximum. In SSB I would not exceed the 500W limit.

As I said before, you have to be aware that you don't have a full-size monobander! Nevertheless, one hears a lot from overseas and what one hears, one can also work, as the tests proved. So I can personally say that the purchase and installation of the MINI-32A was worth it in my case. On the higher bands I'm back in the action and the log is filling up more and more with DX stations. Thus my final conclusion, "HOT" and not junk.

By the way, one more remark. When choosing an antenna, the Mosley-Mini 33 (3 element Yagi, same dimensions as the MINI-32A) caught my eye. This is the first development of a minibeam by Mosley. The differences in gain and V/R are negligible and so the decision was in favour of the lighter MINI-32A.