Data Interface for Amateur Radio

It's not so long ago that, curious about PSK-31, I figured-out that I could receive by sticking headphones to my PC's microphone, and send by sticking the rig's microphone to the PC's speaker.  It worked a treat to get me into the digimode, but it's hardly ideal.

So, round and round the internet I went, looking for anything that might distill into a sensible consensus on which data interface might be any good.  I think at this point I should invent the Rowlands Rule: the internet is a place for everybody to shout their opinion, and shout others' down; thus, no consensus is possible.

I had recently downloaded HRD, a fine package that carries an advert, or link to G4ZLP's web site, this being Neil, who makes digital interfaces by hand (you can, reassuringly, see where pencil marks have been made to guide the drilling of the holes for cable connections to be made!)

G4ZLP's DigiMaster Datalink interface receiving WSPR at the MW1CFN station.

I decided, after a bit of looking around, and wanting to do my bit to support homegrown enterprise, that I'd go for Neil's DigiMaster Datalink interface.  This comes in at an astonishingly good price of £69.99, well below the price of interfaces sold by the big outlets, and it doesn't need any jumpers to be bought or installed, just the appropriate PC-rig cable, another £8 or so in my case.

So, mindful that I'm not much of a computer nerd, have very little patience and no electronics knowledge to speak about, how did it go?

Well, 24 minutes after the postman gave me the box, two cables were connected up and I was sending WSPR signals out across the world.  After a few weeks of using the interface flat out on WSPR and PSK-31, and exploring other modes, I can honestly say there are no issues with Neil's box of tricks at all.  A very minor gripe, which probably applies to other interfaces as well, is that occasionally, there is a need to tweak the output level, which seems to me to drift a tiny bit, possibly with temperature, I'm not yet sure.  Maybe it's just my green-behind-the-ears-ism!

So, a big hit, and without having any link to Neil at all other than as a satisfied customer - of whom he seems to have very many - I'd recommend you get hold of one of his interfaces, which come in a variety of levels of complexity and capability.

Very nice work, Neil!

Update: 1 Year On.

Well, the old box has sent thousands of data messages across the world over the past year.  Sadly, on its first anniversary, Neil's interface decided to develop a fault.  It seemed to wake up to software using CAT control, but not always those (such as PSK/RTTY) using the data cable alone.  The TX/RX LED couldn't decide what mode it should indicate.  It appears to be an IC problem, but I have no ability in electronics. Neil also hasn't seen the problem before.

I've ordered another unit and cable, and Neil is still responding to emails very promptly.  The old unit is happy once it's had a few test signals passed through it, but it's a bit dicky on PSK (using DigiPan.)  It's surprising it gave up within a year, but put in perspective, I operate heavily every day, so compared to the weekend user, it would probably have lasted several years.  I don't think it's excessive to replace a £59.99 interface every year or so, given the fun and DX entities it provides. I still recommend the unit, certainly.

New unit arrived within two days of placing an order, back to transmitting like mad within seconds of plugging it in.  Thanks Neil!

Where are the Regulators?

Amateur radio is, in concept, a self-regulating service that doesn't often include heavy-handed state involvement.  That, to many, is the way it should be.

But when that self-regulation fails, what then?

I write this morning as, for the second time this week, some idiot or other is busy sending a whopping signal over the WSPR frequency, rendering that mode utterly devoid of any but the most powerful signals.

Why not shout louder?

Those keen to wipe out others' activities will say 'ah, but there is no such thing as a reserved frequency for any mode, so shut up!'  That's the attitude of the insensitive and uninterested in the genuine spirit of amateur radio.

To be fair, competitive, stamp on all others attitudes are in fact encouraged by the very societies that otherwise see it as their Very Important Duty to protect the bands.  DX awards, contests, it's all very macho, aimed at making the individual the most important thing, not the manner in which he operates or how he respected others.  Inevitably, many amateurs come to believe that they may do whatever they want to fill their logbook.

A good idea.  But is it really working?  I don't think so.

This is a very sad state of affairs, and I can't see things getting any better.  Listen to a pile-up.  Maybe record it and listen to it a few days later.  Is this what attracts youngsters to the hobby?  Listen to the digital parts of the spectrum.  Hear how everything is played over everything else, because their signal is more important than somebody else's, it seems.  Is that attractive to newcomers?

Self-evidently, the overwhelming domination of the hobby by retired white men is doing the hobby no favours at all.  In the words of the latest RSGB report "it's difficult not to conclude that, in the past ten years, our membership has aged by ten years."  That's a polite way of saying: in another 15 years, those societies are dead in the water.  The hobby would seem to be in the same boat.

The societies have a moral duty to investigate how the bands can be better policed and how enforcement can be ramped up, especially across national borders because, often, it is only from afar that you can hear those responsible.  Something akin to a radio 'Interpol' is required, and required urgently.

The future for amateur radio if we carry on like this...

So, next time you find yourself shouting down the mic in order to be heard by someone far away, just remember that you are as far away and exotic to him as he is to you.  You can make it another day.  There's probably someone more interesting a few kHz down the band. 

Be happier you didn't follow the crowd, didn't just add to the shouting mess, and that you took pride in how you operate. 

There should be an award for that.

Friday Was WSPR Day...

WSPR is a peculiarly fascinating digital mode. You need do little more than check your antenna is still standing and that the ALC isn't kicking in as the rig and PC attend to themselves quietly in a corner.

I find WSPR satisfies that endlessly-burning question in me: where is my signal getting to? I was never interested in contests, just where, how, and why my signal gets to where it gets.

WSPR lets you do this without calling CQ 2,800 times in a day, and gets you a real, numerical signal report that is much more meaningful than a well-intentioned 59 from someone who had to ask for your prefix six times before he gave you the perfect report!

So, here's the result of putting out 5W - quite a lot by WSPR standards - into my delta loop on 20m for more or less a complete day during mid-December 2012. I was especially happy to be picked-up by WA2YUN on Wake Island in the north Pacific - somewhere I previously had never heard of but now know a lot about:

A day of WSPRing.  Most VK/ZL, but certainly not all, was via the Long Path, as was Wake Island. The thicker the lines, the longer contact was maintained.

VA3AQB Guest Post - A 15m Moxon Antenna Project

My Canadian friend, Alan, VA3AQB, has recently been busy making a rather fine version of a Moxon rectangle antenna.  He just about beat the onset of wintry weather, and already, we've managed an easy QSO on 15m using his lovely antenna, which came out ahead, by about an S-point, of his commerical hybrid quad on the day of the test.

Here is how Alan went about it, which includes material kindly provided and approved by KG4JJH:

15m Moxon Project

WSPR Around The World.

WSPR is one of those things that I kept coming across, but knew little about.  In fact, I had no idea other than it was some kind of beacon mode, and I knew nothing about those, either.

Then, one day, the penny dropped.  I was looking into JT65, another weak signal digital mode, and then came across WSPR in the same software package known as WSJT.  For WSPR, though, I use the standalone package for that mode, known simply as WSPR (free).

Screen shot, showing WSPR signal waterfall.

The main problem at this station for some time has been the lack of a proper digital interface.  I decided last week that enough was enough, and took the plunge with Neil, G4ZLP's USB interface, which really is hand made, and got me running on all the digital modes in less than 25 minutes from opening the box and having no previous digital experience at all.

The only problem I did come across was signal stability, which is very demanding for digital modes - just +/- 1Hz is the ideal, and beyond 4Hz, the software will struggle to decode the signal.  My TS480 is pretty stable, but only if it doesn't run too hot or cold; it needs to settle down into an undemanding routine of sending some, listening more (which is how WSPR is meant to work, anyway).  It's changes in the crystal temperature that are the problem, not which temperature it's at per se.  Too much on and offing of the cooling fan introduces big swings in the stability of the reference crystal; I won't be forking out even more money for a temperature-compensated one, which is anyway not perfect.  In practice, swings of +/-3Hz don't seem to affect the received coverage much, but I now have it down to about -1Hz, which is more than acceptable, given the equipment.

Getting out on 20 metres and above is no problem; a multiband, 4:1-fed delta loop cut nominally for 20m works a treat.  But 30 and more especially 40m were not so good, as I had to rely on an end-fed vertical that struggled to get out well on low power, and it is a very noisy antenna on 40m.

The spark of inspiration then hit me.  All those hours of reading antenna literature paid off.  If I can't and don't want to put up a 20m-long dipole for 40m, why not put up a half-delta loop?  This is just 1/6 wave high - an old and partly broken fishing/crappie/squid pole does the job for me - and 1/3 wave as a sloping horizontal section to the ground.  The antenna is grounded into copper water pipe sections driven into our superb ground, fed with coax into a balun or other common-mode busting device.

That's all there is too it.  Earth connections are to copper pipes or rods that provides the other half of the antenna, but use a 1:1 balun or ferrites for the coax!

We all know about antenna images, but it all seems somehow unlikely, somehow unreal.  But I can tell you that reality proves the theory!  Within a few minutes, my 4W signal was reaching Australia during the evening - something I could only dream about with my vertical on 40m.  The noise level for the band has crashed, and now I can clearly hear real 40m SSB DX signals from antipodean points.  Over the next few days, I'll try to talk to them, as well!

So there you go.  Full delta loop performance, with low-angle DX pattern for 40m (matches up on higher bands, too), for half the wire, half the space, and no stupidly-tall vertical structures to contend with.  Who couldn't do with an antenna like that?

Which HF Antenna Should I Get?

Don't worry!  This is not going to be a post about whether a 3 element yagi is better than a hexbeam or some typical drivel.

In fact, it's a headline aimed at getting some search engine hits so that beginners can read this, a second update, celebrating my first complete year of relatively casual operating, showing just how much can be achieved without splashing-out on expensive ham equipment. 

Regular readers may recall I bought my first rig off E-Bay, costing me a modest £270 for a very nicely kept Kenwood TS-50 that is still fully functional.  I've since bought a TS-480SAT.

£270 got me this excellent rig to start off my ham career.  It's still working strong.

 
My first antenna for about two months was just a long piece of copper wire strung from the ATU's 'wire' output, out through the wall, up 5m and then sloping down to the bottom of one corner of our garden - about 23 metres of wire, chosen for no particular reason.

I could only run 50W out of that antenna due to the difficulty in matching it due to wild impedance changes.  On a few occasions, I got some hefty RF burns to my PTT finger, but they weren't things that hurt for any more than a minute or two!


Despite all this, I still got out daily to the Caribbean, the US, all of Europe and even once into VK.   A very poor antenna system, but the thrill of making it to VK-land with that wire is an excitement that was very much relished!

Can't do real DX with simple equipment?  Rubbish!  An indicative map of my first year's operating with 100W SSB and a delta loop antenna.

 
Big guns will say 'yeah, but your signal was rubbish!'.  Well, not that bad, as I hit the back of the VK's beam at the time!  And it misses - completely - the raw excitement of making that far-off contact when you've never done if before.  Filling you logbook every time you press a button is, perhaps, not quite so satisfying.

Since then, I discovered the joy of delta loops - and loops in general.  I use full wave loops in various shapes from 20m HF operating to 70cm satellite downlink, and they are very easy-to-match antennas.  I can't see that I will be moving to anything else any time soon, although my elevated, sloping ground and rural location does maximise the performance.

What were the highlights of the 2011-2012 operating year for me?  Often, they were not long-haul DX, although getting into Antarctica was certainly an exception!  After all, the bloke on the other end doesn't think he is very exciting for being where he is.  He's just 'there', whilst I am 'here'.

No, the memorable ones are made special for their humanity and for transporting my imagination to another place.  A man talking to me yesterday on 10m through his 5W handheld into the KQ2H repeater in New York, out with his dog in Central Park. 

I painted much the same mental image when I had a QSO with a VK/mobile station.

Then there was the VK mobile station, where I could clearly hear the dusty road and engine noise as he thundered across the vast Australian outback to his home, about 2 days distant.

A maritime mobile station in port in Brazil - and hearing the same OM off Sierra Leone and then Australia.

An elderly, wheelchair-bound man in Ukraine, saying he never saw anyone and wouldn't know what to do with himself if it were not for amateur radio.  I often think about that man.

A contact on an otherwise-empty 15m band with a Peruvian station, special as it's where my eldest daughter lives.

Finally, a Spanish station honking his horn, saying, "You see?  Real mobile, eh?"

Cheers!  How HK3C imagined me!

They all made me smile, as did the esteemed HK3C - John Bartlett's exchange with me just before last Christmas, when he created in his mind a picture of me sitting with velvet slippers and a dressing gown as I sipped some Ruby Port at the operating chair!   Not far off, John.  Not far off at all...


So, all I will say to those, like me, who have held back from either getting into transmitting, or becoming an operator at all, is: get hold of a delta loop!  I do keep banging-on about this, but there are very good reasons why.  Here they are again:

(1) Cheap.  You can make one out of any junk wire, and so long as you can use a tape measure and cut some wire (about my level of expertise last year), you can't realistically go wrong. You can even buy a delta for a price less than the wire and a good balun if you don't want to homebrew.

(2) Forgiving.  My 20m loop was 1.5m too long for many months.  It still allowed me to operate the world on SSB, even though the effectiveness of the antenna was clearly compromised to a considerable degree. I only kept it at that length because it was working pretty well and adjusting things tends to cause headaches.  It now sings perfectly on 20m after a few hours of careful adjustment.

(3) In all but the worst environmental conditions (powerline clutter, very hemmed-in situations, etc), delta loop wire lengths are very good at conforming to theoretical predictions.  Use the variety of online calculators and cross-check their output (be sure they are actually different sources, too!) rather than books, as I've found a lot of errors on wire lengths, often ones which have been repeated for years, in many of those!

(4) Simple to erect.  You need just one fishing pole to get a delta for the 20m - 6m bands up into the air, with a base height of about 1.5-2m.  This makes it good for rapid, stealthy deployment.  If you have trees, a delta becomes essentially invisible.  Getting a dipole to 10m, if you have no trees or existing supports, is very much harder and more visible.

(5) You can feed with either a 4:1 balun and 50 Ohm coax at the antenna, or with twin feed to an ATU's internal 4:1.  I suggest you use good quality 4:1 external baluns, such as those made by hand by G-Whip.

(6) An excellent low-angle radiator.  On the excellent mineralised ground here, the peak gain is at 12-15 degrees and essentially the same value - about 2.05dBi - as that of a dipole (typically 2.15dBi), but with an omnidirectional pattern that falls only by about 2dB in the worst direction (in the plane of the antenna wire).

(7) Makes an excellent, easy-to-deploy portable antenna.

So, ignore the adverts, the wildly over-optimistic adverts about no radials and true aircraft alloys.  Just get some wire and start making your own antennas.  Then, start talking to the world!

Happy Christmas for 2012, and have a Great 2013!

Wire Length for 20m Delta Loops

An update on the delta loop is overdue.  I love these antennas.  They turned amateur radio from a noisy, poor signal sort of hobby into one where I could enjoy global DX for essentially no cost.

I've had my moans about how difficult it is to find reliable information on getting a delta to resonance, and I still don't understand why so many different views, because deltas are not especially sensitive to their environment.

Sometimes, you just have to use one of these.  Just not too much!

Anyhow, I decided to go out and do a proper job of getting my delta to sing properly today.  No wind, and a warmish winter day helped.  I disconnected the coax, attached an SWR meter to my old TS-50 running on a car battery, and then hooked up with a short piece of coax to the 4:1.  The whole set-up, radio and all, remember, was outside, working at the antenna itself, with no more than about 1.5m of coax in the connections.

As it was, I knew the antenna was too long.  This was because I stupidly tried, being a bit green behind the ears a year ago, to tune the antenna using the ATU.  This is a very dumb idea for two reasons: meters on ATUs seem not to be so good on cheaper models, and measuring the SWR at the transceiver, rather than antenna end makes the SWR look better than it is because of losses in the coax.

So, a year wiser, I sent a signal into the delta.  The meter read 3:1 at the upper end of 20m, 2.5:1 at the lower end: the loop was, as I knew, too long.  Although it's obvious what I had to do next, you always have that feeling that, when you chop wire, at some point, you'll end up regretting it.  Antennas don't play ball and slowly drop to a good SWR like they're meant to.  They often stop at some value well short of 1:1, and then start climbing.

After a good old chop that brought me back to a piece of tape on the wire I'd marked the theoretically-correct length a year ago - 21.3m - I found the SWR was beginning to bottom-out at 1.6 to 1.7:1.  That's good enough for me, and I expect it would not go much lower, if any with further chops, especially as the 4:1 balun almost certainly brings the system impedance down below 50 Ohms.

Coming back indoors, I found the match at the transceiver end almost perfect, needing no ATU to work 20m and with a near-full 100W going out.

Job done.  I hope!

Delta Loop in the Wind!

Over the past year, I've been exposing my fishing-pole supported delta loop for 20m to increasingly harsh conditions.

Whilst putting the pole up and down is very easy, taking only a minute, it is a bit of a hassle, especially as in the UK, winds tend to blow up, die down, and blow up again over the course of a day.  Constant retraction in the face of high winds is therefore not really ideal.


video-2012-11-02-13-16-48 from John Rowlands on Vimeo.

My pole has never slipped under load.  Slippage happens when the pole is exposed to winds from another direction, because they've already been loosened, and so fall down.  The trick is to stop the sections slipping, which most people do with tape.  This is OK, but it does damage the protective lacquer on the pole, which does have a certain degree of weather protecting quality to it.

Now I use jubilee clips (hose clamps) with butterfly nuts at the bottom of each section.  I got mine in the UK from FEP Hydraulics.  This seems to work very well, in that my antenna has now lived through several strong gales (up to 55mph) from the west and east, with no slippage.

SteppIR vs. Delta Loop - Who's The Best?

It's been windy again this week.  But I'm getting more confident in my fishing pole-and-wire 20m delta loop's ability to put up with hurricane-force winds (a term I use accurately - we have 120km/h or more regularly throughout the winter - and sometimes the summer!)

A wire triangle can't possibly be as good as a beam running power, right?  Wrong!

So, I switched on to find an US east-coast station coming in at a nice 58 or so.  He had a straightforward three element tribander on top of a house chimney, running 600W.

One of my colleagues down in Swansea, meanwhile, called said US station.  He was reported as received at 55.  He was running a three (I think!) element SteppIR antenna, with 400W going out from 40 feet.  Most of us would agree that's a big investment and an excellent set up.  What it doesn't tell you about is the antenna's environment.  Swansea is a highly-developed, urban environment.  My QTH isn't.

A big, expensive antenna does not automatically buy the best signal.

So, I fired a call across to the same US station.  Remember: my antenna is a pocket-money one element delta loop held aloft by a 10m fishing pole with the top 2m removed to allow weight to be carried at the tip.  I was running 100W, probably more like 90W after losses.

Who do you think had the best signal?

Well, it was neck-and-neck: the multi-thousand dollar SteppIR, amp and tower set up was getting the same report as my pocket money delta!

I wouldn't be so stupid as to claim my set up would win in every comparison with the more expensive system, but you do have to accept that bigger, more expensive and more powerful does not automatically mean a better received signal.

Environment is important, perhaps more so than many will accept.  Think about it.  If you want good low angle departure angles for long-haul DX, you need a horizon that is so clear of obstructions that very few living in countries like the UK will ever have that luxury.  Few live within sight of the sea.  Or have high concentrations of metals in the ground beneath their antennas.  We have all of these things, which makes a big difference to how well a simple station can get out.

So before you spend the bucks.  Try simple, proven antennas, especially verticals (which includes vertical dipoles, of course), to see just how far and how well you can reach...

Bi-Square Loop - Fun All The Way on 10m

Yes folks, it's autumn in full swing, as is the 10m band!

For the past week or so, conditions on 10m have been outstanding.  Of particular interest to me is the excellent signal coming across from the Big Apple from KQ2H, a repeater that was once located on one of the ill-fated World Trade Centre buildings.

The bi-square in action.  An 8m-fishing pole supports the top.  Remember that this is not actually a loop - it's open at the top!

And by 'excellent', I am not exaggerating; the signal for hours on end swings to full-scale deflection on the signal strength meter - that's 59+60dB on my rig!

Of course, that's just the repeater's signal; the signal you get into it depends on the usual parameters.

But conditions are not always this good on 10m, and it can be expected that, come the end of this sunspot cycle's peak, the band will be mostly dead.  That makes big investment in a 10m antenna a poor investment choice.

A bi-square, correctly depicted - unlike many other internet resources - as two wires, open at the top.  It is NOT a closed loop!

Enter the 10m bi-square loop wire antenna.  I first came across this truly amazing antenna in 'The International Antenna Collection' book, which compares it against a yagi, highlighting some interesting and often conveniently overlooked points.

Remarkably, this most basic of wire antennas - it is just a loop, open at the top (so not a loop at all!) with both sides pulled out into a diamond shape, each 'leg' being a full wavelength long.  It's fed with twin at the bottom; I use 300Ohm ribbon, to an ATU which makes matching very easy (but do look out for strange effects with twin - keep it well away from other conductive materials.

I once asked a modelling question about the bi-square, and for the record, I reproduce below (in orange) the kindly WB6BYU came up with the following analysis, and interesting points.  I don't disagree with him about full wave loops, but I can say the bi-square has performed admirably from here, often making me the subject of mini-pile ups on KQ2H - all with just 100W, which gets boosted, as a minimum, to about 380W in effective radiated power.  At optimal configuration, this can be as high as 560W EIRP. 

Another useful thing about this antenna is that, if you open it at the bottom and connect one wire to one pole of a 4:1 balun, and a 1m-long counterpoise to the other pole (the other leg remains free), you get a very useful 2-element vertical beam for 20m (see Les Moxon's 'HF Antennas for All Locations').

'OK, I ran some models in EZNEC.  Starting with a 15m Bi-Square loop with the top at 11m.
and the bottom about 1m above ground.  I rounded the dimensions to make it easier to
vary the model.  Then I progressively squashed the loop, keeping the bottom 1m off the
ground, and recorded the gain and vertical angle of maximum radiation:

11m   8.6dBi @ 28 degrees
9m    7.8dBi @ 34 degrees
7m    6.9dBi @ 45 degrees

The vertical angle of radiation increases significantly.  Height is important for low angle
radiation.  In the process the feedpoint impedance dropped from about 3000 ohms at
resonance to 1400 ohms.

Now let's see what happens if we raise the bottom of the antenna rather than
lowering the top (while leaving the top at 11m.)

1m   8.6dBi @ 28 degrees
3m   9.2dBi @ 28 degrees
5m   9.6dBi @ 25 degrees

Clearly the higher average height above ground improves antenna performance, even
though the loop is more squashed.

Now, for comparison, let's look at just the top wires, so a sloping "Two Half Waves
In Phase."

6.7dBi @ 23 degrees

If we use a standard inverted vee at the same height (11m) then we get:

6.8dBi @ 19 degrees

For comparison, let's go back to the original Bi-Square and compare the radiation at
these vertical angles:

8.3dBi @ 23 degrees
7.7dBi @ 19 degrees

And we can check a full wave loop with a top height of 11m at the same angles:

7.6dBi @ 28 degrees
8.1dBi @ 22 degrees (maximum)
7.9dBi @ 19 degrees

So while the Bi-Square loop has a higher peak gain, the standard full wave loop has equal
or better gain at lower elevation angles.

Let's see what happens when we lower it:

9m  7.1dBi @ 28 degrees
7m  5.7dBi @ 39 degrees

(This is without squashing the full wave loop, which would raise the average radiation height.)

While the Bi-Square may be fun to experiment with (and should give a good match to 50 ohms
using the common window twinlead that is around 400 ohms impedance as long as the antenna
is square), I'm not sure there is a lot of benefit to using one at low height compared to a full
wave loop, or possibly even a dipole or inverted vee with the same top height, especially if
your primary objective is DX.'

Satellite Working - Cheap Style!

Some months ago, I started taking an interest in working satellites on FM.  I built a lovely 2m, 5-element quad, which shows very strong gain and even stronger directionality.  It quickly came into very useful service for remote repeaters (up to 158 miles so far on 1.8W!) and for more local work.

But that's where satellite progress stopped.  Always too busy with one thing or another.

So, with clear autumn skies telling me to get a move on and make my 70cm downlink antenna, I went to see what junk I had to cobble together.

I like quads, so my 70cm antenna is a 7-element quad, built with one supporting arm per element because at 70cm, when using hard drawn copper, the elements are mostly self-supporting.   I used standard online calculators, which don't always give good results, to guide my wire and spacing lengths, and, for once, this did yield a good antenna.

The completed 70cm, 7 element quad.  Works a treat, even if it looks a bit rough!

The boom is just 25mm x 25mm pine, with lightweight timber square section spreaders, all heavily varnished for the weather.  If you are building one, use moderately smaller section boom timber, as this one proved a bit too heavy for comfort, especially if operating two antennas at the same time!

Connection is just a short length - about 60cm in this case - of junk RG58/U, which has very minimal losses over such a distance, connected directly via spade connectors at the driven element.  There's no need for a balun or matching section, especially as this is just a receiving antenna for this purpose.

Does it work?  Yep!  I wondered why, with 10+dBi gain, I wasn't hitting one of the toneburst-activated 70cm repeaters even when directly underneath is.  Thiss seems to be a problem with the stability and tolerance of the 1750Hz tone, now rarely used due to CTCSS taking over, on my very cheap, but otherwise very good, Chinese handheld.  Using a pure tone did access it, even from inside the house.

And on satellites?  Excellent!  Easily picks up SO-50 as soon as it hints at coming over the horizon, with very clear, stable signals at about S 6 across the vast majority of the pass (SO-50 transmits with only 250mW at launch).

Very pleased indeed!  Total cost: about £6 in all new materials.  Essentially nothing if you have bits lying around. Just remember to make it as lightweight as possible.

Update: I made my first sat QSO with EA7HZZ using the antenna for downlink.  I used just 4W into the 5 element 2m uplink quad.  Not bad!  I'm now making plenty of contacts on each pass.

Next step: Operating two separate antennas is too cumbersome, so I'm going to build one of these tape measure antennas, again at next-to-nothing cost.  I'll mount the quads on a motorised mount some day.

An example of a 2m tape measure sat beam.  This gets the signal up fairly well, but the 70cm receive antenna is too weak for SO-50 unless it has an unfeasible number of elements.

Update on the next step!  I built a lovely 2-band tape measure antenna for higher elevation passes, and managed to get a very good match on both.  But, and as is my experience with quads vs. yagis, the yagi is very much poorer in performance than the quads. The yagis are also much, much harder to get to the right resonance and match than quads.  All that said, I have managed good QSOs into SO-50, showing the 2m yagi is adequate at 3 elements, but it is rare that I can hear my voice clearly coming back, though others seem to hear me fine.  That, then, must be down to the 70cm antenna's gain - I have no such difficulty at all with the 7-ele quad for 70cm.  I really can't say it was worth making this antenna because of the fiddly matching and performance issues, and that a non-elevated quad system works very well for most passes.

Yagi vs. Delta Shoot Out!

Well, having come up with a lightweight, strong design for a 2-element loaded yagi, up it went, by moonlight, for tests the following early morning.

A 2-ele beam like mine.  Large, and needs to go up high.

Now, I was not able to put the beam up at anything like a good height - just 6m, though the ground does slope away sharply in front of it.  So what follows isn't an assessment of what the beam could do if it were at greater heights.

I turned the beam towards the long path signals from the Pacific.  Running at the other end of our large garden, away from any interaction between them, was my trusty 20m full wave delta loop which uses vertical polarisation.

Wow!  A SteppIR in a very macho scene.  It gives a good impression of the sheer size of even a simple 2-ele beam.  But the sad reality is that experienced beach operators will tell you that a simple vertical antenna easily outperforms a yagi from the seaside.  So 'beam' doesn't necessarily mean 'best antenna' for all locations.

Luckily, VK3VCE and VK5PAS were in a group that were only too willing to report on the two antennas.  The result?  The beam was between 1 and 2 S units down on the delta loop.  This was confirmed later in the day, when a station on Prince Edward Island also came in 2 S points down.

Propped up by an 8m fishing pole and made of any old wire, the delta, with its base at just 1.2m, beat the far more complex beam by anything up to 12dB.

So, in terms of decibels, that's a beam, at this height, returning 12dB less in and out firepower than a simple delta loop.

Now, again, the beam wasn't being given a fair chance, and it is a centre-loaded, shortened version.  BUT!  Let's look at this from the perspective of ease of deployment, use, and cost.

The beam is complex to get up into the air.  Books and magazines suggest it's easy, which it is if you have lots of money, plenty of room for guy wires, and permission to put a mast of some sort up.  For real hams, it's really very difficult; have a look at how wrong it can go if you're not prepared:



Then you need to rotate the beam.  This adds considerably to the expense, and necessarily means you'll have to twist your antenna around endlessly to get the best signals.

Then you'll need to make the whole thing windproof at, for 20m antennas, anything from 8-15m high, depending on whether you have any ground reflection sweet spots.  For me, with regular gusts to 80mph or more, this is a big ask, or a recipe for endless upping and downing the beam.

Big antennas can mean big disasters and high repair (or insurance) costs. 

Given that my 2-element beam would appear to have to reach at least 10m before it broke even with the delta loop, with an apex at 8m, supported by a single, $15 fishing pole and which resists winds to about 50mph quite happily, the beam loses the competition, hands down so far as my essential check list is concerned.

Low angle patterns typical of low-mounted, vertically polarised deltas.  This one's at 5m; at lower base heights, the upper lobe vanishes.  Low angle patterns are very useful for DX, and the delta excels in this respect.

Now, my QTH does have a clear aspect, is elevated at about 65m around the surrounding land, has some sea views, and has the best terrestrial ground you could hope for.  So a delta may not work quite so well from a cluttered environment, where a yagi placed above the neighbourhood would yield real benefits.

Just keep in mind that, whilst a horizontal beam sounds like a good idea, the reality isn't necessarily so.  

The Compact 20m 2-element Yagi

Living in a windy location, as I always go on endlessly about, makes for a difficult existence as a radio operator.

Over the past few months, and despite the atrocious operating practices often to be found there, the 20m band has become my favourite band for DX.  All of this has been with a simple 1-element delta loop for the band, which though simple, is exceptionally effective from this undeveloped hilltop, metal-saturated ground location.

KA3DRR's lovely 2-element yagi - yours will look much the same.

Recently, I decided to pursue a simple 2-element beam for 20m, to see whether the added complexity of  getting a beam several metres into the air is worthwhile.

I'd been looking at this easy-to-follow guide for some time, and had long ago built the coils, but never completed the antenna.  Inspired by some calm weather, out I went to add some wire and start tuning each element individually, rather than take a chance on the published measurements, build the whole thing and then find it way off resonance!

I also found this guide on a very similar antenna to be excellent and well worth downloading and keeping safe.

Although the peculiarities of the metal saturated ground make this site quite unique, I did find that the element lengths (using kevlar wire) needed to be considerably longer than published, and that's allowing for the fact I wanted my beam mainly for the SSB parts of the band.  Kevlar wire is thin strands of copper wound lightly around a kevlar core, and may well behave very differently from flexweave or drawn copper - you'll have to experiment with your own wire preference.  The big advantage of kevlar is that it's about three times lighter than flexweave, which is a consideration with saggy fishing poles.  The drawback is kevlar's higher cost.

VK2ZAY's image of a loading coil shows how simple it is - just some known length of wire wrapped neatly around  PVC tube.  Even I can make these!  Keep the coils neatly wound by wrapping firmly in weatherproof tape.

In the end, I found that each half of the dipole, without the coils, needed to be 114.5" (2.91m) long.  In other words, the length of each bit of wire either side of each coil (of which there are two per driven element) is 57.25" (1.455m).  I did try 3m poles, but they proved too flexible at the ends, so with only a modest penalty if increased weight, I used the upper few sections of an old set of 7m poles, with most of the thinnest, uppermost tip cut away so it doesn't sag.  Poles are very cheap at about £7 each from Paul's Angling Supplies (also on Ebay), who have superb service standards.

Detail of the boom to spreader joint.  A single screw goes through the spreader timber into the boom, which is then strengthened with varnished plywood screwed as shown.

 
The reflector is built a bit longer and in accordance with general design patterns for Yagi-Uda antennas - about 5% or so (you can spend all week reading up and chasing different web articles about precisely how long you may want to make it, but you have to start somewhere, so 5% is a good guide!)

The boom is varnished timber, with simple timber just strong and wide enough to accommodate the poles and to tie cable ties around to keep the poles in place (this is by far the lightest, cheapest way, but use quality ties).  I'll need to fashion a short stub from timber and plywood to attach the whole thing to the as-yet-unavailable push-up mast, but that's pretty easy. 

Here's an idea of the size of this antenna - note the garden fork for scale. 

In theory, the antenna should produce about 4dBd forward gain, with a modest 10dB front-to-back ratio.  In other words, if you take a standard rig at 100W and put this antenna at the end of the coax, you'll end up with about 250 watts effective radiated power going off to your target.  Signals to the rear will be reduced by about 2 'S' units.  Not bad for the price of some wire and fishing poles!

As soon as I get enough money to buy a simple aluminium push-up mast and get the beam at a decent height, I'll let you know whether all the effort is really worthwhile, relative to a simple delta loop propped up with one 8m fishing pole, and which needs no rotator or rotating!

One interesting point to note, well made by my friend John, ZL2JBR, is that you can often find signal 'sweet spots' at certain mounting heights, which you need to find for your location by experimentation (sticking the antenna up at maximum height, then watch your 'S' meter for any changes as you lower it bit by bit).  John, for whom I have great respect in understanding radio, reckons that the increase in signal strength can be as dramatic as 10dB.  Given John is pretty much the only ZL you will hear on short path most days, and that his antenna is several metres lower than usual theory dictates, his practice certainly matches his ideas!  For reasons of reducing mounting difficulties and wind loading, any reduction in height is a welcome thing, believe me.

In the meantime, if you don't want to build a beam, remember that you can make this in the 1-element dipole flavour - a 20m dipole made of super-lightweight fishing poles that's about 40% shorter than a full-sized version, all with very minimal reduction in performance. You can even collapse the poles for stowing out of view, or for taking portable.  You should also be able to turn this into a moxon rectangle following some experimentation.  Or you could, with stronger supports, fashion some end capacitance hats and shorten the elements further.  Plenty to keep you wasting miles of wire, there...


UPDATE:

I found this beam to be a poor performer at 8m.  It was 1-2 'S' points down on my 1-element delta loop for 20m.  I think the tuning of the elements could have been better, to be honest.  That said, it did get across to VK with no problem on long path, but that isn't actually very difficult.  Beams are simply too complex for me to bother with at the moment, because of the need to mount them so high and that they catch so much wind.  The delta easily wins again!

Any Antenna Is Better Than No Antenna!

It's a saying newbie hams hear very often: any antenna is better than no antenna!

The saying encourages hams, often completely lost as to what antenna to buy or make, to simply get anything that will accept RF energy and radiate it towards some distant land.

Take two of these (preferably without plastic bits that isolate one part from the other) and connect up some feeder and an ATU.  Voila!  An antenna that will get you out across Europe, maybe beyond.

What many green-behind-the-ears hams don't realise is that there is an awful lot of metal stuff that will act as an antenna, albeit not very efficient ones in most cases.  Plenty have connected two metal step ladders or shopping trolleys to some coax or twinfeed, and managed to get out to at least one skip distance - typically about 1000 miles.

So if you are really confused by the adverts that claim their  antenna is made from aircraft alloys and will deliver real DX (whilst costing you much more money than it should), then try two bits of wire for a dipole, or some step ladders (which, admittedly, cost quite a bit if you buy them new!)

Poor Jerry had to listen hard, but the simplest of wires did allow a QSO - if only just.  Much better than no antenna at all!  Image: PH9HB

As a case in point, I normally use a delta loop, itself just a triangle of wire, but which is a very capable antenna for global DX, especially from my uncluttered, elevated position with good ground (I live on a metal deposit!)   But today, it was a very strong, blustery northerly wind, gusting about 45mph.  The delta can take that sort of wind, but I prefer not to chance it too much.

So, with very little time on my hands, I put up an end-fed wire as a sloper from a 6 metre fishing pole in a hurry.  I was lucky enough to hear PH9HB/AM somewhere over Hungary at 39,000 feet.  I gave him a call, and he heard me, albeit at a weak 3/3 report (short of not being heard at all, my worst ever report!)  Still, we did manage a confirmed QSO, which is more than I would have done with no antenna at all!

Geoff Brown, G-Whip, makes these lovely matched end-feds, which rarely need an ATU, and deliver very good performance at a low price.  The Hawaii Emergency Radio Club also makes a very effective, multiband version.

So there it is: proof positive that, even if your signal isn't contest station quality, any antenna really is better than no antenna!   So connect something up, and forget the conflicting bravado on internet forums, which serve only to make things worse!

A 2m J Pole For Under £10

The 2m band has been interesting me recently, especially as a few superrefraction events have been occurring with wild temperature swings in our bizarre UK summer of 2012.

Having knocked-up a very successful and very directional 5-element quad for 2m, I found myself with the age-old problem of beaming myself out of the action in other directions!  With a good view out to sea and over the surrounding landscape, this isn't such an ideal situation unless specifically chasing contacts across in Ireland or when the skip is running further afield.

The J-pole used to put me off making it, but having this one knocked up for a few quid, I really don't know why that was.  See the lead flashing on the roof?  I connected that with a 9:1 unun and counterpoise once.  It just about got out to first skip distance, but I don't recommend it, not least for safety reasons!

So, I decided to have a go at a J-Pole for 2m.  The usual criteria applied: cheap, readily available materials, preferably those commonly found around the house or shed, and a price as low as possible.

I had a look at one commercial outfit kicking our J-Poles for 2m, and was astounded at the price for such a simple antenna - nearly £150 if you choose all the mounting hardware.  OK, it's well made by a reputable company, but even so, £150 is a lot of money for what is little more than two bits of tube.

There are a few design guides out there in interweb land, but this one is a particularly considered version, which appeared in CQ magazine at some point.  Use these dimensions and you won't be far off that hallowed ideal SWR figure.  You can find an interesting discussion on the performance of a J Pole here.

Mine ended up a shade too long, but even so, the SWR was only about 1.5:1, so perfectly usable, especially with a tiny hand held kicking out 2W.  The SWR was off only because I'd extended a shorter, random tube with a copper connector, and hadn't accounted for it's length.  I trimmed half an inch off, replaced the end cap and the SWR was down to about 1.15:1.  Signal reports are very good, so this is a keeper.

I did follow the experience of the article's author, and electrically isolated the antenna from its mount. Initially, I used a very short piece of plastic barrier pipe between two compression fittings, but this proved too floppy to use.  So I ended-up just shoving a good piece of snugly-fitting garden cane up the antenna's innards.  This is nice and stiff, and of course entirely insulated for mounting on a metal or other pole.  In future, I think I'd replace the elbows with tees at the bottom of the antenna, so that two canes or other support could be inserted, as this antenna is quite top heavy and needs good support.

Remarkably, the savings from building this J-Pole over buying a commercial version can be enough to buy a basic 2m rig!

If you have to buy all-new materials, I can't see this costing more than about £10.  I had everything lying around, needing to buy only one copper tube bend and some jubilee clips.  In effect, it can cost you essentially nothing to build, and certainly leave you with enough change to buy one of the cheaper Chinese < 2m rigs.  Quite a saving!

UPDATE:

There's a modified J pole that has considerable gain over the standard construction, known as the 'Slim Jim'.  This is just another half wavelength of copper tube added parallel to the long tube of the J Pole, and of course connected to it.  I converted my J Pole with very little difficulty - you just need a flat surface or a clamp to align all the tubes up properly to solder.  You also need a simple spacer; I used plastic tube with notches melted into them (a nasty business - do it outside!) with hot 15mm copper tube and kept in place with cable ties to keep the tubes parallel long term.

I was pleased (I think!) to find the SWR had lowered to just above 1:1 on conversion, and I didn't need to adjust anything at all.  Signal reports are good, as is the reception - repeaters at 60 miles and simplex stations at 70-80 miles have been heard so far, and it's no problem to access the most useful local repeater at 21 miles on 2 Watts.

Transformed: a J pole converted into a Slim Jim.  Valuable extra gain for another piece of copper.

  
Gain is reported to be about 2dB over the standard J Pole, which brings it in at about 5dB overall.  That means my 2W handie output gets magically upgraded to 3.8W, which is rather useful on such low power.  If you're using a mobile rig with 25W, the Slim Jim will give you 48W effective out, and on 65W, 125W effective out.

An 11dBi 2m Quad Beam for £8

There's nothing like a British summer to get hams out in the open, building antennas.  It's been so damp and dull this year, when a nice day comes along, you get through a week's worth of work in a few hours!

So, having completed the very successful vertical dipole, I built a small 2m quad with 2 elements.  The boom and supports were all made with bits of pressure-treated wood going free down the local woodyard.

Looking good in a summer sky: the 2-element 2m quad.  Good for at least 40 miles simplex on 2W.  All the wood was waste from a local woodyard, and free!

This worked really well, and got out to 40 miles simplex quite readily.  It also had reasonable F/B figures, whilst not being so directional that you became isolated from very local nets.

But it wasn't good enough, with just 2W from my handie, to get across the Irish Sea from Anglesey, as I couldn't get into a /M station up on a hill above Belfast one night.  Cue: make a bigger quad!

A really good 5-element quad for 2m is to be found (with dimensions that work!) in the ARRL/RSGB book 'International Antenna Collection'.  The author built in wood, which is a good choice if you want to make cheap antennas quickly.  Wood for internal use is fine, and will last many years, so long as you get it made into an antenna and varnished-up quickly.

It's got a long nose because I hadn't enough wood to add the final director element!  It still managed nearly 100 miles simplex on just 2W.  Total cost: £8 (wire was junk).

I Just offset the narrow support crosses for the wire on the sides of the boom, rather than drill holes for dowels as is done in the book version.  I also didn't cut notches for the wire, preferring just to use time-served cable ties to secure the wire.

Does it work?  Well, I hadn't bought quite enough wood to finish the project, but with four elements on the boom, I stuck it in the air at about 3m on a temporary pole.  It should have a gain of about 9dBi (11dBi when completed!), magically turning 2W into 9.5W (15.4W when complete).

I could hear some weak signals towards Belfast, but the accent of the operators wasn't right; I turned the antenna south of the border to find the signals were in fact coming from Co. Wexford, with EI9GGB in QSO with EI9GLB.  I made a break call - using just 2W - and was heard straight away by GGB.  I was 56-7 to him, 44 to GLB.

94 miles simplex on 2W from a £34 handie into an £8, unfinished antenna.  That's my kind of amateur radio!

A few days later, I broke the 100 mile barrier with a 56 into G8XVJ/P above Leek in Staffordshire, working an RSGB contest.  I had to wait until the worst of the 59+s around him were finished, but come on - it's just 2W from 101 miles away!  I also managed to open the GB3CP repeater in Co. Fermanagh, and even managed a QSO with GI4UHP/M, though my signal was not very strong.  Not surprising, at 150 miles!

Now with the final director added, we should be at 11dBi gain.  Time for a proper mast, too!

Mind you, I have to admit I am tempted very much by the nice-looking, lightweight 8-element 'Scorpion II' quad for 2m as sold by Cubex.  That's a very good price for an antenna of such gain (~14dB, turning 2W into an astounding 30W), so long as the UK import duty bureaucrats don't get hold of it on the way!

UPDATE:

A word about  feeding.  Most 'advice' online tells you that a 1/4 wave matching stub is necessary to bring a good match on this antenna.

This is not true!

To prove it, here's the result with the 1/4 wave stub in place, as shown on my recently OSL-calibrated SARK-110 analyser:

A 1/4 wave stub yields 100 Ohms impedance, and a high SWR.

Rather obviously, this is the wrong impedance and a fairly high, though entirely usable, 1:8 SWR.

Dispensing with the stub altogether, connecting directly to 50 Ohm coax, the SARK now yields this ideal result:

That's better!  Good impedance, and a <1.3:1 SWR.

 So there you have it!  For this multi-element quad, a direct 50 Ohm coax feed is the correct arrangement.

A Bare Bones 'I-AM' End-Loaded Vertical Dipole

Spurred on by the compact size and excellent, near delta-loop performance of the copper pipe end loaded vertical dipole, and with a warm evening on offer, I set about to make this antenna something manageable by a real human.

The aim: because copper pipe is heavy, not very wind resistant and expensive, I wanted to make the antenna very much lighter, much more wind resistant and made of stuff likely to be in most hams' sheds.

So, I had lying about:

• A 10m glass fibre fishing pole 

• Some unused 2.5m long moulded wood edging strips (a coving shape is strong and lighter than square section; round profiles are not very strong and less easy to work with in general).

• Random bits of kevlar wire and enamelled copper wire

• A good length of 300 Ohm twin feed and dipole centre (homebrew, of course!)

What I did:

Take out the top three sections of the 10m pole, as they are not needed for this design and anyway are too flexible to carry any weight.  This leaves you with a sturdy pole about 6m or so long.

Use cable ties ('ty wraps') in a cross fashion to fix the timber edgings to the pole.  I've changed this now to use simple plywood clamps using bolts and wing nuts.  This allows the whole thing to fit into the smallest of cars, with minimal set-up/down time or complexity.  Try to keep the clamps as small as possible, to keep the weight down, especially for the top end load.

First attempt at a lightweight clamp so the whole thing can go portable in a small car and not be a headache to set up or down.  It works a treat, but do keep the top clamp as light as possible, to avoid top-heaviness.

I took about 2.5m or enamelled wire, bent it in two, and scratched half an inch of the enamel off at the centre point.  I then made a small connector, initially out of flexweave (anything will do), but now recommend, for durability, you use solid copper, with a spade connector attached to one end.  I soldered the other end to the centre of the copper wire.  The whole wire was taped onto the timber edgings (cable ties are better for more permanent versions, and you should lightly exterior-varnish the timber).

Solder a small wire and spade connector to the middle of the end loads.  Makes for easy disassembly.  After a year of testing, I now recommend you use solid copper for the tag, not Flexweave or similar.

I did exactly the same for the bottom end-load.

I then took some old kevlar wire, which is very light, robust and collapses into a manageable lump that doesn't readily get tangled when you collapse the antenna.  The length was just over 5m (this isn't that critical).  Both ends of the kevlar had spade connectors put on, so that the whole antenna can be dismantled easily if needs be.

Finally, I connected the dipole centre to the kevlar wire, and used one cable tie to attach the centre to the fishing pole.  Again, I'm going to make an easily detachable clamp for this, as I don't like to clutter the environment with wasted nylon ties, and it's less convenient if you have to cut ties all the time.

Nearly down to car size.  The collapsed end-loaded vertical dipole, just a fishing pole and $2 timber edging (with wires!)  Performance of the fully-deployed antenna is just under that of a full wave delta loop on the 20m band.

Connect up the 300 Ohm twin to the ATU and: voila!  A fully-functioning low angle DX vertical dipole that collapses into a 1m-long package that easily fits in a small car.  Total deployment and take-down time: about 1 minute apiece.

Proof that this is light: very light!  An adult can easily balance it on one finger.

For mounting, I use my trusty cement mixer tripod (actually, it has four legs!), onto which a standard 2" aluminium pole of about 1m is put onto the spigot, and then the fishing pole sleeves over the pole.  It's very sturdy even in heavy winds, though some simple rope guying is best, as is putting a couple of heavy cement blocks or stones on the feet of the tripod.

This is probably going to be my permanent portable antenna, and the one that will get deployed when it's blowing an 85mph gale at home.  It performs almost as well as the full wave 20m delta loop, which is no mean feat.

The antenna working clifftop 'graveyard portable' from Llanbadrig Church, Anglesey.   On this evening, conditions were not good on HF, but I did manage the US west coast and Japan on 50W SSB.  Not bad for a made-for-peanuts antenna!

Thanks to the late Les Moxon, who inspired this design from a 2-element wire vertical beam in his excellent book HF Antennas for All Locations.  The more you read this book, the more you realise how good it is.

Incidentally, the 2-element beam is just 5m in height, needs only about 2m ground clearance, and for me, worked ZS and VK easily on the first outing, suspended - badly - from two bendy fishing poles!

UPDATE:

During a visit to the toilet, I belatedly had the brainwave of trying telescopic whips for the end loads, so that the whole thing could become even more compact and portable.  Finding good quality whips of the required length isn't that easy, but very reasonably-priced units are sold by Buddipole.

Update (2018 July):

I've started operating at a rural shack that really brings out the best in this I-AM.  I also want to start working at beaches and other places more often, as the domestic environment continues to worsen in terms of RFI for most of us, and will hit me, sooner or later.

To that end, I find that the end loads, which are effectively capacity hats, have too much mass and result in either 'head nodding' for a flexible mast and timber/fibreglass arrangement, or an antenna that is too massive overall in the case of an all-aluminium version.

The answer is to build disc-like capacity hats instead.

In early tests, using ARRL Antenna Book formulae, I could just about match the antenna with an internal ATU on 14MHz, but only above 14.260MHz.  The discs are obviously slightly too small.   I could only match-up on all bands 20-6m when the lower end of the antenna was about 30cm from the ground.  Normally, that means excessive ground coupling - and unacceptable losses.  But this was during excpetionally (as in 50+ year exceptionally) dry conditions where the water table has lowered substantially over normal levels.  In wetter conditions, the antenna would probably match at a greater height.

Even so, I did manage good contacts with, for example, A41 land on FT8, with decent (equal) signal reports both ways. A quick WSPR test for about 30 minutes also showed very good comparison with other stations.

All that said, I am going to make end discs that are a bit bigger. For this, to provide physical robustness and self-support, I've ordered some 2mm copper wire for the disc radials, and some 0.8mm wire for the outer ring.   Each disc simply slips over the fibreglass mast, making for an antenna you can roll up and carry in your hands or backpack.  More details when I complete the exercise...

And here's a wind test, when I was on-air to PC1H, DL1HA and ON9CGB, at 40mph (64km/h), gusting about 48mph (77km/h) with one rope guy to a concrete block, just mounted on a pole placed loose on a cement mixer stand (two concrete blocks to secure). I'm happy this could take significantly higher winds :

DSCN7844 from John Rowlands on Vimeo.

Following discussion on QRZ.com's forum, and a tongue-in-cheek suggestion from G3TXQ, this antenna shall now and forever be known as the 'I-AM' (!)  

Go build!