Antenna Tower Disasters

It's always interesting to try and learn from others on the internet, although most of the time, you come away feeling less informed than when you began!

There's a very useful web site and seller of replacement parts in the UK for the Versatower-type masts, which can be found here.

Putting up a tower moves you from simple wire operator, where life rarely gets more complicated than replacing a broken support, to a much more complex sphere of activity.  Towers are expensive, heavy, require a lot of careful attention to avoid accidents and failures, and can't just be considered something that can be deployed and used no matter how severe the weather.

Load up your tower (and stub mast) with too much, and this is inevitably the result, especially in windy locations like the UK.

Understandably, when you obtain a second-hand tower, you want to start climbing it, sticking as many antennas as possible on it, and generally just staring up at the glory of it all.

But I'm not sure why some people report tower disasters are somehow unexpected and a great shock when you see that, as on the above web site, people not only sticking too many antennas on ultimately quite narrow gauge masts on top, but also flags, verticals and all sorts of other wind load-enhancing materials.  Try holding a half or full-sized flag in your hand during a gale, and you'll get a good idea of what it does to a tower.

So, if you find your ideal second hand, or even a new tower, then do try and visualise the forces acting on that thing.  It is, in essence, a very large, very heavy lever being pushed from above by the stronger winds up there.  It may be made of steel, but that can, under the right conditions, buckle like cardboard.  It can also kill you or seriously damage your property.

My advice?  Consider whether you want to spend what I think must be a minimum of £2000 even with a second hand tower, by the time you get a rotator and antenna up there, and whether the modest gain of perhaps an 'S' point or two is really, really worth it.  If it is, then make sure you site your tower very carefully, load it with the minimum of antennas, keep it well serviced and ensure all your insurance is in order.

Hams: Are We REALLY Emergency Providers?

Over the past few days, I've been impressed with the very positive relations many hams in the US have with emergency services.  There's little doubt that, unlike the UK, the authorities in many states of the US do actually take hams seriously and see them as a potential resource, almost entirely independent of the complex infrastructure that can, as has so often been proved, fail quite spectacularly.

In the US, ham emergency comms is valued more highly than in the UK, where it is mostly now treated as a joke.

Since the introduction of the latest Civil Contingencies Act, and drawing on my own correspondence, there's little doubt that hams in the UK have been relegated to 'no longer needed' status.  Reasons cited to me are various, but include: the law doesn't require amateurs to be involved any more; everybody has a mobile phone in their pocket now; there are fewer hams than there used to be, etc.

Try managing a civil emergency when there's no network.

So, bleating on, as hams are apt to do when their hobby is threatened in any way, that we provide an essential service, seems destined only to fall on utterly deaf ears from now on.  Raynet has done sterling work, but, like most of the hamming scene, is seeing many ops dropping off the old age end of life, to see no newcomers take their place. 

What is really unfortunate is the failure of local authorities to see how multi-layered and complex the provision of mobile phone signals actually is.  They seem oblivious to the wide-scale failure of networks in large metropolises like London and New York, sometimes as a result of weather, sometimes being down to just technological breakdown. 

In a very real sense, local authorities, at least in the UK, appear to have put all their trust in the expectation of a mobile phone system that, as they see it, will never fail.  That, and the typically-British tendency to believe that, somehow, despite all the scaremongering about terrorism, those mass civil emergencies won't really ever happen.

Well, we'll see how things pan out. When the weather went Arctic the last few years here in the UK, it was independently-minded and resourced folk with their own 4x4s that kept essential health staff coming to work and rescuing stranded individuals.  It wasn't uncommon to see police and council vehicles on their sides whilst Joe Public carried on past them.  There's little reason to see why, when mass public comms systems fail in future, hams would not, in fact, have a similarly effective and immediate solution to offer. 

But we, as a hobby, do need to realise hamming is no longer perceived to be of any real value in the UK's preparations for emergencies and disasters.  If we don't, we run the real risk of sounding desperately out of touch with political reality.  A real educational push is required, and soon.

Lighthouse Weekend - Wow!

A brief note of thanks to all who went to the effort of setting up stations at a very large number of lighthouses across the world this weekend.  It's been a real ball!

I think the LH weekend is one of the most positive and attractive events of the whole amateur radio year.  You get a wide range of interesting DX plus some fascinating insights into the lighthouses themselves.

For the 2014 visit to the Skerries, I hope to take a radio or two for LH weekend.

 
I was very happy to work One Fathom Bank in Malaysia against a heavy load of ugly shouting and anything approaching civil radio operating.   One elderly gentleman in Iceland bravely came back for more on Sunday after being bullied by a massive and ill-tempered lot into giving up on the Saturday.  If you don't get a firm grip on the pile-up, it does tend to bite you.  Unfortunately, few modified their behaviour to accommodate the considerable age of the op.

So, next year, I think I may take the plunge and get out to the Skerries off Anglesey.  It's probably time to start planning the permissions and boats for that now, so I'll let you know how things shape up.

Weekend Operating Tip

I would hardly call myself an operating expert, but it's always nice to pass on any tips that may help new ops.

When I began hamming, I had an old Kenwood TS-50S that didn't have a properly-functioning tuning spinner; it turned at the same slow speed, no matter how quickly one turned it.  To skip along the band quickly, you had to press a certain sequence of keys, which would then speed things up a lot.

You can really get to hate this crap...

This turned out to be a big advantage that allowed me to pick up DX calling CQ that I would almost certainly not have detected had I been spinning the tuning knob.  Even with my newer TS480, which does spin at varying speeds, it's still too slow to scan across the band quickly.  Luckily, HRD lets you tune with any steps you care to input, restoring the TS50's rapid tuning of old.  You can use the keyboard or mouse wheel to do this.

So, step one is to avoid the DX cluster.  By the time it's been put on the cluster, there will be a flood of people with stations much better than yours piling in to start shouting like madmen, so chances are you won't get a look in (though by all means, have a go; sometimes you will get heard!)  Avoiding the cluster also means you won't spend half a day chasing one callsign when, had you left it and gone tuning around the band elsewhere, you may have grabbed many more - or something even more exotic!

Step two is to employ any method - your rig's controls or software - to rapidly hop up and down the band.  It's surprising how quickly your ear tunes to weak CQs being called in distant lands that haven't yet been heard by anyone else.  This is one of the key methods of securing good DX when your station is fairly simple, and pretty much how I completed the first 100 countries. 

40m Delta Loop - Going Flatter

As the autumn bares its teeth, it's that time of year again when evenings will see 20m close, and reliance put on 40m for night-time operations.

Last winter, I threw up a half loop for 40m, fed against ground (radials would, of course, be less lossy!)  It received very well indeed, and had very low noise.  But it wasn't all that good on transmit.

So, time for something else.  I've never found horizontal antennas work very well from this site.  Time to put up another delta loop.  At 42-43m round trip, that's a big loop!

43m of wire held up by a rather flimsy 8.5m of fishing pole (centre).  A tall tree is much better!  At right is the 20m loop, which has put up with five years of Atlantic winds by now.  That open horizon makes for good radio!

Luckily, there is no need for perfection when it comes to loops, with flattened ones - up to a point - even exhibiting a slight increase in gain over an equilateral one.

So, I gathered various bits of wire and soldered them to form a 43m-long loop.  I worked out that, with a standard 10m fishing pole, using 8.5m due to the weakness of the upper sections, I could, on a less than windy day, get about 10-12m of sloping wire either side of the apex up in the air, with 18-20m forming a very long base wire!  It connects at one corner, for mechanical simplicity, to a 4:1 balun.  If I had any spare, I would have used twin wire to a balun outside the shack as the losses are much lower than in coax.

It works!  I've run a standard quarter wave vertical against the delta on WSPR, which allows semi-objective testing, and within the limits of propagation variability, they perform identically, putting out the best or very close second best (within 1-3dB) signal to DX stations on 40m from the UK (or indeed anywhere else across the EU!)  The best signal on the test evening, incidentally, was another welsh station running a 160m doublet up at 16m - itself quite a beast!

No well-intentioned '599' here.  My flattened delta is usually in the top two strongest signals to LA9JO from anywhere in Europe.

A loop this big is ungainly and gets in the way of normal garden use. It also needs a relatively large - or at least a long garden. But if you can squeeze it in, it's ideal for 40m nighttime use during winter and can be matched-up for use on higher bands.  At 20m, the first harmonic, you could be looking at 7dBi gain at 20-30 degrees departure angle, taking you into 3 element yagi performance territory or beyond for the price of some wire.  It won't, however, be the best antenna for local NVIS contacts, for which a low-hanging dipole will obviously be much better.

 For very windy days, a much sturdier non-conductive support will be needed, or a tree.  Sadly, trees will be a little hard to come by in my garden for the next 20 years or so, so I will look yet again at buying a pole or two from DX-Wire.

A Tale of Two Baluns

Baluns are an important part of most wire antenna systems, and as such, are a basic component in many stations.

Of course, this station encourages you to build your own - it is, after all, very easy, provided you have a clear wiring diagram (authors: take note) and take a reasonable pride in your work.

For an experiment some time ago, I needed a 2:1 balun, which I did not then have the confidence to make.  I opted for the American-based Balun Designs LLC who, for what must be said is the fairly high price of nearly $100, duly provided me with a slightly customised unit.

In Balun Designs' case, you certainly do get what you pay for; the high price does at least reflect the very high quality of winding and putting the whole thing together.  Mechanically, the support loops are much too heavy for my liking, and even have a tendency to slip.

Have a look at the lovely Balun Designs 2:1, which is a company, I should note, I have no relation with other than as a customer:

Neat and very well-made.  Balun Designs' 2:1.

Compare the above with a 9:1 unun I bought from a totally different seller about the same time.  It's made by a fairly high-profile UK-based seller who, to avoid any tendencies towards filing spurious libel suits, must remain unidentified.  All the more surprising, then, that on receipt, the very thin plastic enclosure had already cracked.  It wasn't down to the postman, but to the fact the enclosure was too small for the stuff shoved inside it!

Forcing a transformer into a box that's too small isn't clever, even for the relatively low price tag.

The core and wire was just too big for the box, and for some bizarre reason, super glue had been used to try and stop the post connections from slipping. No doubt the seller would claim I didn't complain, but then, why would one expect to have to complain about a box that's too small for the transformer inside it?  I put it down to experience, and recycled the core into my own, much more neatly-made unit.

And that's just the point.  Look at that 9:1.  Are you seriously saying you can't make one of those - and put it in a better quality, better-fitting box?  I say you can not only build it, but save yourself a load of money and learn about transformers at the same time.

Go make!

Collinear Delta Loop

I'm a huge fan of delta loops.  They have, in their various guises, made it around the world with me over the years.

Sometimes, I add a longer, reflector loop for certain paths, typically into Africa, which is never an easy direction from here.  But it's a bit of a pain to arrange, and spacing tends to vary wildly if the winds are up.

So, a different way to get about 4-5dBi total gain is to connect another, identical loop to the feedpoint, and run both as a collinear array.  By way of comparison, this the same gain you would get with a hexbeam antenna, but that would need to be some way up in the air for best effect.

For an extra 'S' point of gain, just run two loops from the same feedpoint.  Easy!

Result?  The deltas can flop about relative to one another as much as they like, it makes no odds.  The matching is only marginally affected, and signals take the predicted 'S' point leap upwards.  What's more, it's dead easy to run up the extra delta on a fishing pole, and then bring it down again if there is no real need for it, or the neighbours are PITAs!

So, hexbeam-like performance for the price of two fishing poles and some wire.  That's cheap hamming!

Pyramid Loop Antenna (20m version)

As summer slowly relents to autumn here in the UK, it's time to get low-height, efficient antennas going before the onslaught of hurricane winds begins.

Recently, I wrote about my WSPR tests of a half lambda DDRR antenna.  This got to most parts other antennas were reaching, but usually much more weakly.  It did manage to get into Wake Island in the Pacific on 5W output, although the actual radiated output was probably much less.

It was time to put that experiment to bed for a while, and recycle the wire into a full 20m loop (which works out at 21.3m in this case!)  But, to keep the height low, and because I had always been interested in the antenna, I decided to fold the antenna on itself, creating what is usually called a 'pyramid' loop.  This is what it looks like (don't heed the dimensions for 20m, they are for another band):

Easy peasy!  Seems to be a good performer, too.  It's easily scaled, without taking a whole field, to cover 40m (6m per side) or 80m bands (12m per side).

I took an old, broken 7m fishing pole and used only the first 4m sections.  These are quite thick, so hardy in the face of fierce gales.  It's cable-tied to a stout fence post, giving it plenty of support.  300 Ohm twin is cable tied to the top, and the two ends of the loop attached to a twin-feed dipole centre.  The loop is then pulled out with stakes and light rope.  For DX performance, keep the two triangles reasonably vertical; a flattened-out pyramid will give a higher peak radiation angle.

WSPR tests shows this antenna performs really well.  It's too early to give meaningful numerical comparisons, but on its first evening of operation on 20m, it's achieving very much the same signal strength at DU1MGA as other UK stations, so it's obviously not a bad antenna in any sense.  What's more, with each 'leg' only 3.5m long, it easily fits in a very modest garden of the sort often found across the UK.

I haven't determined the precise radiation pattern as yet, but a quick near-field assessment with an RF meter seems to show nice, strong vertically-polarised radiation from the front and back, and horizontally-polarised, possibly mixed polarisation from the sides.  I'm useless at modelling, so will have to rely on others to do so.

4:1 Current ('Guanella') Balun - Made Simple.

I was never an electronics whizz.  That often means I need others to show me how to make things.  I like making things.  It saves me lots of money and I develop a sense of understanding for the components.

It's thus a great shame that so few people who claim to be experts volunteer clear guidance on making things.

Thus, it gives me great pleasure to reproduce EA6XD's wonderfully simple and helpful diagram on making a 4:1 current (as opposed to voltage) balun.  All you need are some ferrite cores, some wire and connectors.

A current balun is widely held to be better than a voltage balun as it forces equal currents in the two halves of the antenna.  Forcing equal voltages with a voltage balun does not, apparently, force equal currents.

In building a windom such as in this example, it's much easier to have the balun at ground level than weighing down the centre of a dipole, unless you are using a tree or equally sturdy support.  If you want to use it on some bands, it needs a 1:1 and not 4:1 balun, so having it in a tree is a bit inconvenient!  In that configuration, you feed the balun with a short length of coax to the ATU/transceiver - it can be in the shack or just outside - and then some twin to the dipole centre.  A useful starting point for lengths etc can be found here.

If you take your time, you'll have the satisfaction of beraking free from expensive, commercial baluns that are sometimes of a criminally poor quality, and rarely of a current type.  Total cost of these units, including an IP65-rated enclosure (E-bay usually provides!), comes in at about £8 or so.  You can drill a hole for the SO-239 socket using a normal drill or a blowtorch-heated piece of 22mm copper pipe.  I prefer the hot pipe because it produces a clean hole; drill bits tend to 'catch' the plastic and make an irregular hole.

One final piece of advice: once you've put this in a watertight enclosure, make sure you drill a small vent hole where any water getting in can drain away and the unit then dry out.  I found that water slowly gets blown in via the tight but unsealed coax socket (this is a very windy area) so you need to add a gasket of silicone or similar to stop this.  Alternatively, you can pop the balun under an upturned flower pot or something!