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Introducing the MM17


#1

Aerials eh? Potentially a contentious subject, but always a hot topic for us lightweight portable SOTA ops. Unfortunately, while I am quite good at doing the maths bits for aerials, things go pear shaped when I need to start any practical work. I’ve rarely managed to fit a plug without the SWR going through the roof, and just don’t ask about the soldering iron and the Bencher paddle…

But fortunately, I’ve got a couple a local mates who are not only practically adept, but are SOTA activators. Richard G3CWI got me going with halfwave dipoles for 80m and 40m, which have always worked really well for these bands. A 30m dipole has recently been added to increase the fun. (The 40m and 30m dipoles also work acceptably on 15m and 10m respectively).

My other friend (yes, I’ve got two, I’ve never been so popular) Sean M0GIA has lots of ideas. Some of them are dreadful. Some of them are inspired. International SOTA Weekend must count amongst the latter. His converted CB aerial for a multiband HF vertical, without doubt, one of the former. A great big shiny metal rod with dual purpose - an effective lightning conductor for the summits and the most elaborate but functional dummy load you ever used. Great on receive, flat SWR, but the effect of a mesmorizing inverse amplifier on transmit. Truly astonishing.

But then he comes up with an idea (hardly original, but still a good one) to chase the horizon using a vertical 20m antenna with a groundplane. Four bits of wire and a feeder. And did it work? Yes - I instructed him that he had to hand it over to me in return for some leafeting I did for his XYL, and proceeded to work the world on 5 watts from the summits - UA9, JA, VE, W, LU etc, 599 both ways being typical. Although the theory of how the antenna was effective was simple to understand, its performance had a certain “magic” about it. “Magic M0GIA” was mentioned, soon after which the antenna became known as the Magic Moggy.

I immediately informed Sean that I wanted one making for 17m. Sean got straight to work on this, and I only had to deliver about 2200 more leaflets and wait several decades before he made me one. And Thursday 27th May 2010 was the night it would debut.

Jimmy M3EYP was at a scout event at Barnswood in the Staffordshire Moorlands with his mate Edward, so it was an easy decision to utilise the two hours of downtime. I continued up the hill to Gun G/SP-013 and marched to the summit.

I set up the MM17 with the driven element elastic-banded to the very top end of the SOTA Pole, meaning that the feedpoint was about 7 feet off the ground. The groundplane radials, also acting as guys for the pole, were angled at about 30 degrees to the horizontal in this arrangement.

I was about to kick off when I realised I had left my phone in the car - so there would be no self-spot. Fortunately, my alerted QRG of 18.077MHz CW was clear, and double-fortunately, well-known SOTA chaser Laci HA7UG answered my very first CQ call. This was great, because it meant I could ask him for a spot, which he kindly provided. Many thanks Laci.

I then operated continuously for fractionally over one hour making 36 contacts into 18 DXCCs, which were: Hungary HA, Poland SP, Austria OE, Germany DL, Slovakia OM, Croatia 9A, England G, Belgium ON, France F, Russia RA, Wales GW, Italy I, USA K, Switzerland HB, Denmark OZ, Ukraine UT, Serbia YU and Greece SV.

The architect of the MM himself, Sean M0GIA came out for a stroll to the summit, to check on the progress of his latest creation. He arrived as I was putting QSO number 30 and DXCC number 15 into the logbook, so was soon musing about the MM12 and the MM10 projects!

If the evening couldn’t get any better, the sun was out, the sky was blue, and the colourful panorama from Shutlingsloe, over The Roaches and down to Tittersworth Reservoir was stunning. OK, as “views from the shack” go, it’s not quite in the league of Ailsa Craig GM/SS-246, Great Gable G/LD-005 or Slieve Donard GI/MM-001, but still pretty good.

Radio traffic eventually dried up just after 8pm, perfect timing for me to break everything down and drop back down the road to pick Jedward up from the scout camp. A most enjoyable evening. Thanks to Sean M0GIA for the excellent MM17 to go alongside the MM20, and to all the SOTA chasers that came on to work me - it is really appreciated, thank you.

73, Tom M1EYP


#2

In reply to M1EYP:

How about taking that 20m MM and adding links like we do for the linked dipoles? That way you could do 20m,17m,15m,12m,10m,6m,4m, and 2m all from the same GP antenna. Okay 8 bands might be a link too far but ‘Shack and Bake’, mix and match the bands you need.

73 Steve GW7AAV


#3

In reply to GW7AAV:

How about taking that 20m MM and adding links like we do for the
linked dipoles? That way you could do 20m,17m,15m,12m,10m,6m,4m, and
2m all from the same GP antenna. Okay 8 bands might be a link too far
but ‘Shack and Bake’, mix and match the bands you need.

I had the same idea while reading Tom’s post. The link dipole should work also in vertical direction. Due to the weight a “snapped” dipole might be a better choice though.

73, Jaakko OH7BF/F5VGL


#4

How about taking that 20m MM and adding links…

Simply because I prefer to use single band antennas and most of my activations tend to be on one band only. Simple, easy and very robust. For each activation, I decide what band I want to do in advance, select that antenna and put it in the rucksack.

On the rare occasions that I have done a multiband operation (like ISW) I must admit to have rued not going down the linked approach, although having said that, it was so cold and windy on ISW that I was pleased not to be going out changing links, just staying huddled in the tent swapping which feeder was connected to the 817!

Tom M1EYP


#5

In reply to M1EYP:
Hi tom, are there any plans to release a guide to build one of these, so the rest of us can have one of the MM antenna’s?

Thanks
Adrian
2m0etr


#6

Hi Adrian,

Once I have agreed the royalty situation with M0GIA then…

Seriously, it hardly needs a guide. It’s four lengths of wire cut to quarter wave, and some thin coax feeder. One of the lengths is the driven element, and that is taped/elastic-banded/velcroed/cable-tied up to the top of the pole. The other three lengths form the ground plane, and have lengths of guy line from the end of them.

I hope I’ve got that right; Sean M0GIA will add further know-how no doubt.

Tom M1EYP


#7

In reply to 2M0ETR:
I use this antenna calculator http://www.csgnetwork.com/antennaevcalc.html

Select a 1/4 wave and cut slightly over say an inch…easier to trim than add!

The first MM is here http://homepage.ntlworld.com/s.amesbury/M3FVB/20m%20port.htm

I dont believe the angle of the radials makes much difference. Have fun. Sean M0GIA


#8

Anyway, onto the activation report for Friday morning, 28th May 2010. I was up with my alarm at 5.50am BST, and almost ready to set off when XYL Marianne got up as well. Others with teenage kids will acknowledge the rarity of a husabnd-and-wife conversation without nosey parker offspring constantly butting in. I took the opportunity to put the kettle on and make us both a mug of coffee, and enjoyed an all-too-rare opportuntiy to sit and have a natter with the Mrs.

Hence it was a relatively late pull off the driveway at 6.27am (hey, my accuracy and memory for these things is getting disturbingly Gerald-like) and I was commencing the ascent from Cloudside at 6.50am. The weather was lovely with sun and blue sky, just like Gun G/SP-013 the previous evening. In fact there had been heavy rain in between, but it was certainly a glorious morning now.

On the final ascent to the summit, I noticed that there were now quite a few green shoots emerging all over the formerly heathery hillside, recently decimated by fire. Whether this is nature taking its course, or the result of remedial plantation, I do not know.

With the antenna quickly aloft, I was eager to compare a morning operation with last night’s evening activation. Again, results were very good, with a snappy QSO rate and rarely a moment of respite without the next caller tail-ending the previous. In 26 minutes, I made 23 contacts into 11 DXCCs: OM, RA, HA, OZ, S5, SM, F, OE, DL, LA, UT. One station had the call “OU5T” which seemed very unusual, although it is a Danish prefix. Usual searches on QRZ and Google have drawn a blank.

So just two outings with my new MM17, and already 59 QSOs in the bag. It’s a winner. Now to actively chase the DX with it I reckon.

Tom M1EYP