The Ultimate 20m Stealth Antenna?

This weekend, I spent far too many hours repairing the old, rotted wood around a flat roof - the kind of roof that is impeccably unsuited to the UK climate - yet is very widespread.

Luckily, this was just a small porch, and I didn't yet want to spend a lot of money building a new roof for it.  Instead, I covered up the OK-but-a-bit-rotted wood with some brass metal.

Never let bad neighbours and planning authorities put you off amateur radio!

Hurrying to finish the job before it rained yet again, I realised the total length of metal was just over a quarter wavelength at 20m.

You know what's coming...

Yes, what better way to babtize my new rainproofing than to hook it up to some 300 Ohm ladder line running to a 4:1 balun, add a counterpoise draped over some bushes, and connect up via an ATU.

I set it off on WSPR this morning at a relatively high output of 2W, although this has to be set against the more typical output for 'real QSO' digimodes like JT65 and JT9 of about 10W.

First, here's the map of stations hearing me, and stations I heard with the porch over some 22 hours:

Next, only the stations that heard me over the same period:

And, finally, how the porch compared with the best WSPR station I know in the UK, who was running 200mW, some 10dB less than I was:

It's a remarkable observation on my QTH that a porch antenna continued to get spots during the depths of the summer night, whereas a full dipole didn't.  Clearly, you wouldn't get this kind of result from a developed neighbourhood inland.

Overall, my peak distance using 2W comes in at precisely the same as the full dipole running 10dB less power, which gives a handy ballpark figure of how much the porch is 'down' on the dipole.

I think that's quite a remarkable result, and one that could never have been reached so objectively before the advent of WSPR.  My spots signal-to-noise reports at 2W from DX stations broadly spanned -16 to -26dB.  So, it's clear that running a more typical 10W with JT modes would certainly make this stealth antenna of practical use, with the proven potential to work the world.

Whilst I was writing this, I noticed something rather remarkable: Alaskan station, KL7L, was receiving me (with the antenna now more of a vertical than yesterday's horizontal efforts) at -23dB, one of only four EU stations he was hearing at all over the past couple of hours (and two of those were using stupidly-high outputs of 10W and 50W - on WSPR!)   Here's the evidence:

A simple tweak that will improve the antenna significantly is to turn it into more of a vertical configuration.  I simply took the 'counterpoise' and threw it up over one side of the roof.  That then becomes the radiator, with the porch metal becoming the return path.  Here's how the results look.

First, all stations hearing me:

I wasn't able to compare with the GI station yesterday, as he wasn't operating.  Instead, I compare with another 'reference' WSPR station, running an inverted-L antenna.  Ignore the dip in my signal at centre, caused simply by the WSPR software being terminated by my laptop for some bizarre reason:

Finally, a plot of the spread of signal strengths, relative to the inverted-L:

Altogether, it's clear that the wire thrown up on the roof, with the porch metal acting as the counterpoise, works really very well.  The reported signal strengths in VK, for example, are around -26dB S/N, which certainly puts them within reach on JT or other weak signal modes.

There is, rather obviously, no claim here that, where you have the space and friendly neighbourhood, you should put this antenna up instead of a full-sized antenna in the clear.  Instead, it started off simply as a 'let's see' experiment that reveals that, for difficult neighbourhoods and small spaces, this throw-it-up stealth antenna really can work well on weak signal modes.

Amateur Radio - The Future

I quite often read, with some despair, at the increasing problems folks in towns and cities are having with radio intereference. I often come to the conclusion, though negative, that there is little hope of things getting better for the HF community in the shorter term.

The RSGB is taking a harder line on RFI, but they are having to lobby OFCOM - a regulator that often appears in the news only for populist matters, like hitting the odd illegal marketing callers, and making money out of spectrum sales. 

So the RSGB, unless it takes on some much more effective lobbyists, is hoping against hope for any effective help from OFCOM.

Is there, then, any point in getting my children, or yours, involved in radio?  Well, without the proliferation of RFI, the answer would be a resounding 'yes!'  There are simply so many aspects to radio that one can spend several lifetimes learning, doing and enjoying.

But, RFI is proliferating, perhaps at its highest rate ever.  No doubt there will be some technological innovations that might see some RFI sources vanish.  But history shows us that the radio spectrum has only ever become more and more crowded, and conflicts more common. 

Even professional users with vast investments in equipment, such as amateur astronomers and environmental satellite operators, are increasingly suffering from RFI.  What hope, then, a handful of amateur operators that, in the UK, perhaps so they can't complain about a lack of services, don't even have to pay for their licence?  

My advice to kids is to remain fleet-footed, in all aspects of life.  In radio, it means maybe having a fairly inexpensive home station, but always with a mobile or portable station fully ready for deployment.  That way, one can always simply have a day out, away from the worst sources of RFI.  At least there is some futue in that manner of operating.

Antenna Planning Insight (UK only)

Every year or so, I try to update readers on any planning issues that may help them put up antennas, or otherwise keep what they've put up.  Accordingly, none of the following is advice, but merely an account of experience that may help you consider aspects relating to your own situation.

A recent discussion with the RSGB's planning adviser, John Mattocks - himself a retired Planning Inspector - highlighted a feature of antennas that you may want to keep in mind if you either apply for planning, or apply for a certificate of lawfulness for what you have after a period of four years where you did not apply in the first place (which makes the installation lawful, from a planning perspective (i.e. not from a listed building, etc. perspective, which is covered by other legislation and may affect your installation in addition to planning matters.))

Let's review a few important aspects before we get to that discussion:

(1) Antennas and their associated structures become immune from enforcement, and therefore fully lawful for planning purposes, four years (no, it is not ten years) after the installation was "substantially completed".  A reference to the relevant legislation is provided at the end of this post.

So, in this situation, if someone tries to get under your skin, saying that you put up your antennas without planning, suggesting you did something wrong and that they can 'get you for it', you categorically did not!  It is not a criminal or other offence to develop your land without applying for or getting planning consent.  Only if and when your council comes to challenge you through an Enforcement Notice, and you fail to comply with that Notice and/or fail to comply with an Appeal that goes against you, do you come into conflict with the law. This, of course, is very different from saying you should develop your land without consent!  It all depends on where you live, and what the people around you, if any, are like.

(2) It goes without saying that, in order to be certain of successfully challenging any planning officer or Enforcement Notice, you should take very many photographs of your installation from the very first day you put things up.  Towers need large amounts of concrete, so keep your receipt from the ready-mix supplier as independent evidence.  Please take photos of your antennas in their environmental context so that changes to features such as your cars, kids, hedges, etc, can back up the claim of a passage of time.  Because you also want to defeat any claim that your antennas were not always up, you should take photos regularly for four years.  Every day might be overkill, although easily possible with today's mobile devices and digicams, but at least every week might be appropriate.  It has been held that a period of 18 days where structures were not in place is enough to defeat a claim of permanence.  So don't leave too much of a gap between photos!

(3) You are in no way legally obliged to apply for a Certificate of Lawfulness after the exemption from enforcement period has been reached.  Cost, though modest, is one reason why you wouldn't want to.  Stirring up needless bureaucracy is another, especially if your evidence for having antennas up for four years or more is a little weak.  If your evidence is strong, then you may wish to apply for a CoL, though the recent personal advice from the RSGB to me is to 'let sleeping dogs lie'.

(4) A council that decides your antennas are not immune, but cause insufficient harm for them to bother pursuing it to an Enforcement Notice, will send you a letter that tells you this.  Councils do take a moment to assess harm, sometimes according to a set of fixed criteria, and are directed by central government to try and negotiate with you before running to their lawyers (because Courts and Appeals officers dislike those who don't try to settle their differences informally first). Indeed, the Planning Inspectorate advises that negotiations to settle matters informally continue even during the appeal process.

In effect, the Authority that chooses not to pursue matters will then be telling you that they are acting on their discretion not to use their powers of enforcement.  So you can, in practice, consider the installation as immune from enforcement (the council could not reasonably go back on their published intention not to enforce at a later stage (so keep all letters/emails safely!)

Councils also tend to try and intimidate you by claiming that selling your house may become difficult owing to a lack of consent.  This is utter rubbish that you should ignore with confidence.  If a potential buyer's solicitor flags lack of consent or Certificate of Lawfulness as a question for you as a vendor to answer, simply advise them that your solicitor will arrange an indemnity insurance.  This typically costs about £50 - which is very much cheaper and simpler than either a full planning application or CoL.  I have never known an indemnity insurance offer not to satisfy a buyer's solicitor, even when it involved much more substantial aspects of a property than antennas.  Indemnities are, in fact, completely standard fare in property transactions.  None of the above is advice, because things vary according to circumstances.  Seek you own legal advice.

(5) Having a tower and antenna on a trailer does not make you immune from enforcement.  If you use it only occasionally, it may be treated as a non-fixed structure and nobody will bother you further.  But there is a test case that found a trailer-mounted antenna system was "operational development", and had to be dismantled.

(6) If you live in a high-density housing setting, then it is exceptionally unlikely that a tower or similar structure will reach the four year (or even four week!) point before someone logs in to an anonymous reporting app that many councils now operate.  If, however, you live in a more remote spot, then you probably have a much greater chance of evading enforcement, provided it is not too prominent from roads, paths and neighbouring properties.

Indeed, such remoteness, if you are lucky enough to enjoy it, ought to be, of itself, a strong argument against the basic 'mischief' of unconsented structures - that there is nobody around to suffer the 'loss of amenity' local authorities use as their very basis for argument.  But beware any surrounding roads or footpaths used by the public, which make you, in effect, less remote.

Now, the important point that John Mattocks discussed with me is: should you apply for planning permission for a tower plus the antennas atop it, or should you apply for the tower and antennas separately?

This sounds like splitting hairs.  But, consider where you have, say, a loop fed Yagi that is grounded to the tower.  Does that make the tower part of the antenna itself?  How about where you attach a half sloper for a lower band, where the 'missing half' of the radiator is indisputably the tower itself.

OK, a council isn't likely to realise, know about, or understand such technicalities of where the electrons are flowing.  They only care about appearances.  But a persistent planning officer may delve into things and seek further advice when confronted with potential defeat when you smile and claim the four-year-rule.

The outcome of the discussion was that it is probably best to split your system into tower and antennas, and make separate applications (or apply for separate Certificates of Lawfulness) for each.  This avoids the potential problems you may face if you change antennas in future, where the entire (perceived as single) tower-plus-antenna structure, rather than just the antenna itself, could then be claimed to have been changed - and therefore the whole damn thing - including the tower you thought was in the clear - needing a new application. 

Some of these points are quite involved and perhaps unlikely to occur.  And in these days of severe budget cuts, councils are doing everything they can to cut out needless paperwork and legal costs, so they are likely to be much less active in the community than during any time in living memory.  But with so many neighbours from hell these days, TV programmes that portray hams as bad neighbours themselves, and councils who often seem to seek new ways to punish the public, it is always best to fight your corner comprehensively.


You can find the Town and Country Planning Act here.

The four year rule section is s171b(1), found here.

TS-480 TCXO

Several years ago, I bought a TS-480SAT from Kenwood.  My first rig was a Kenwood TS-50s, with which I was mightily pleased.   I sold it on for the same price I bought it for, such was the TS-50s's reputation.

Sadly, I became very frustrated and disappointed with the TS-480SAT.  Despite being a superb sideband radio, it had terrible and widely-known crystal oscillator drift.  For some utterly ridiculous reason, Kenwood shipped the 480 with a wobbly oscillator that made it, if not unusable, then certainly an embarrassment on digital modes.  Drifts of +/- 4Hz were typical for my rig.

The 480 then variously saw service for a couple of years as a mobile sideband rig, and then as a manpack unit.

Last week, I decided the 480 should see more use, so I bought an SO-3 clone TCXO from this guy on E-bay.

I thought the unit might come from the US, but it was delivered from China.  It didn't take too long to arrive, and today, in just a few minutes, I installed it into the 480.  Nervously, I soldered the crystal in and switched back on.

Look!  No drift!

To say I was amazed by the performance improvement is this year's understatement!  With this £15 TCXO installed - a saving of about £80 on a Kenwood unit - the wildly-varying standard oscillator has gone, with zero drift, even when the fan comes on mid-transmit cycle.  From a quick look, it doesn't even lok as though I have to trim the crystal any.

It's a pity I didn't grab one of these TCXOs earlier.  Don't hesitate to get one yourself if you're unhappy with yours.

Lightning Arrestors - WSPR Loss Test

I recently improved the RF earthing system at my QTH, mainly driven by a considerable reduction in length of the connection between equipment and the earth rod outside.

Living on extraordinarily acidic soil (pH ~4), there's little point in driving a '10 foot stake' made of copper-clad iron into the ground here; it will simply rot away in months.

 Instead, I use a 1.5m-long 15mm copper pipe, driven into the soft, acidic and highly-conductive ground.  The connection to the ground bus is made with about 1.5m of hand-cut solid copper banding of about 15mm width.  That's the shortest I can physically make it here.

***PLEASE NOTE: PROTECTIVE MULTIPLE EARTH SYSTEMS***

Before you go hammering lots of earth rods into your garden, please make sure you read this free RSGB leaflet carefully.  If you are not sure of anything, contact both your electricity provider and a qualified electrician.  Your house could burn down, possibly with your insurance being invalidated, if you do something that you either don't understand or that isn't according to the regulations, or both.


All this earthing work led me to stick a lightning arrestor onto the earthing bus.  It claims to have 'less than 0.1dB insertion loss', which I'm sure that, at HF, is probably true.

Under WSPR test - a common lightning arrestor unit.

Whilst I can't quickly put an obejctive figure on the losses - that will have to wait for more time to be available - I can run WSPR on a WSPRlite unit at low power (100mW) through the arrestor, and see whether the results cause any concern, relative to past extensive testing, and to other stations running twice the power.


After just 18 hours of transmissions (40% duty), it's clear that passing the puny 100mW through the arrestor doesn't seem to affect the outstanding performance of my twin-fed delta loop.  Clearly, there is bound to be some attenuation, but not at a level that makes any material - or even detectable - difference.

So it seems that I can leave the arrestor permanently in place. If you have many antennas, it's best to use an arrestor for each one.

12 Metres - Not as Predicted.

I've never been a fan of propagation predictions. For one thing, they hardly ever seem to be correct.  Then, there's the fact that published predictions in the likes of RadCom and QST are often entirely unable to account for the minute-by-minute vagaries of the Sun.

Despite this, predictions continue to be published and, indeed, given considerable prominence in magazines and online services alike.

A very good example of propagation prediction is PREDTEST.  Another, and perhaps the best in terms of accuracy, is VOACAP.

The 12m band is as lively as the garden this summer!

Now, if PREDTEST is to be believed, I shouldn't have been able to work well into the midwest of the US last evening on 12m, nor into Brazil.  Yet, for weeks now, 12m has been very busy on digital modes, and some are even giving SSB a go.  VOACAP has a much better stab at it, and gives a clear indication that giving 12m a go would be worthwhile.  Indeed, those with a beam in the US were managing -01 dB S/N reports both ways last evening, so this isn't a weak set of events. 

Now, having invested in a tower and 3-ele LFA Yagi some years ago for 12m, the question of band openness at 24MHz is a rather important one for me.

Not a good forecast.  If you believe any of it...

Whilst I wouldn't put a large bet on the UK-US path being a reliable circuit again today,  I will put my bottom dollar on the band being open to Europe and Russia by this morning's coffee time.


I admire those that try to tame nature by getting ahead of the game and predicting how the bands will turn out on any given day.  But the really good DX often comes in by switching on, finding a 'dead' band, and sending CQ with some persistence.  Soon enough, someone far away will send a response.

SO239 Panel Connectors Supplier

Try as I might, I never seem to run out of projects that demand a good quality SO-239 panel connector!

Even though these are bread-and-butter components, they can be suprisingly expensive when bought through mainstream ham outlets.

Last week, I gave a try of some panel connectors via E-bay, which come directly from China.  Remarkably, within a few days, they arrived in the post. 

Just under £12 for 20 connectors is pretty good value in my book. 

Here's what they look like in the flesh.  Very well formed threads and teeth.

WSPR Power Tendencies

If there's one thing that has been a big development in amateur radio recently, it's the WSPRlite unit.

Whilst this, for the moment, is a transmit-only device, it has really opened up propagation and antenna assessment in a much more objective, bias-free way to the masses.

The WSPRlite unit is programmable to send a minimum of 5mW, and a maximum of 200mW.

What I find really strange is that almost everybody using a WSPRlite sets their power to the maximum output.  There are hardly any units - and there are a lot of units out there now - running below 100mW.

Year after year, my power output foir 'real' QSOs has been getting lower.  I've never used more than 100W on SSB, with digimodes typically using no more than 8W - this all through simple wire antennas.

It's a pity that the machoistic belief in 'more power' seems to continue, unabated.  Just look what this fascinating comparison of my vertical delta loop, at a mere 10mW, against an inverted-L, at 200mW, shows:

Antenna Height: Some Considerations.

Fate delivered me to a spectacularly good home site for operating HF radio.  As a result, I've always been fascinated, from the outset, why this site was so good.

Apart from the most mineralised ground imaginable, the site is modestly elevated at 300feet amsl, with sloping ground to a nearby coastline.

What became clear very early on to me was that extremely low 'take-off' angles are available here.  Measurements in the far field show strong radiation slightly below the horizontal.  In other words, the radiation pattern isn't restricted by the pseudo-Brewster angle as in the kind of normal plots you see, but can be considered 'tilted', such that the peak pattern occurs at or below the horizontal, matching the slope of the ground. 

Now, we all strive to place our antennas as high as we can possibly manage.  But is this necessarily an informed way to proceed?

I modelled a dipole with the ARRL HF Terrain Assessment software, and here is the output with a dipole operating at 14MHz, set at 10m:

First of all, it's evident that this location gives very good ground gain from very low angles (peaking at about 6.5dBi), right across to higher elevations.  It's important to note from the profile that the software clearly cannot cope with elevations that are zero, or are less than zero, so the peak gain should almost certainly be to the left of its drawn position if it were to reflect the reality of down-sloping ground.

What happens if we take the dipole down to a superficially-pathetic 2m above ground?

Very surprisingly, the peak gain shoots up to 10 dBi!  Not only that, but the peak lies on (and, with sloping ground, somewhat below) the horizontal.  At elevations above about 3 degrees, the gain is now in negative territory.

Now, ordinarily, to cover all the potential arrival angles of signals, one might say that the 10m-high antenna is clearly the one to opt for.

But, when there is an additional 3.5dBi - a doubling of gain - available at angles considered to be crucial to best DX performance (think verticals at the seaside), then a very low dipole on a hillside clearly has something spectacular to offer.

Situations where the low dipole might be of considerable interest are (a) long path working of the antipodes and (b) long skip DX to, for example, the west coast of the US from the UK, when other stations are unable to access them.

These are all things that the late Les Moxon alluded to in his 'HF Antennas for All Locations' book, now many years ago. He had a very open, enquiring mind, which make his texts, now rather dated in style, nevertheless still very relevant to those who think radio is all about height and power.