Tuesday 29 January 2013

Antenna Shoot-Out: Mate Loop vs. I-AM

Huh? 

What the heck is a Mate Loop?

Simple: a figure of eight magnetic loop (link is to a similar version and not the one tested in this analysis) that yields a less critical tuning bandwidth than a single loop.

What's an I-AM?  

Simpler: It's one of these end loaded vertical dipoles that yields a dirt-cheap, effective antenna.

Results:

The end-loaded vertical dipole beat the loop by a relatively small but consistent margin, except for the long path VK contact, which was heavily against the loop.

Sample data, 20m band at about 09-10UT 2013 January 29:

To SV8QG: Loop = -24dB; dipole = -19dB
To EK6RSC: Loop = -11dB; dipole = -9dB
To 4X1RF: Loop = -20db; dipole = -12dB
To VK6PG: Loop = -24dB; dipole = -6dB

So, if you want performance, it seems the vertical dipole, which costs essentially nothing to throw together, is a winner in this particular quick test.  The advantage of the loop, of course, is that it can stay up in just about any wind, whereas my vertical dipole, even at 6m, does sometimes need to be brought down.


Friday 18 January 2013

Antenna Planning Permission (UK Only)

A few weeks ago, the RSGB periodical 'RadCom' published a page of advice on the 'four year rule' within planning law.  It's the kind of advice it should run more often, in my view.

Most of us would like something like this.
So why would law-abiding operators wish to avoid planning?  Well, ideally, we don't!  What we would like is a planning system that doesn't confuse our hobby with 'telephone masts' (which no longer need permission!), and endlessly wrings its hands about 'safety', 'radiation' and 'approved antennas', none of which ought to be considered by a planning authority.

Before we get to the meat of planning, remember that you can do anything on your own land (that is otherwise lawful!) in terms of planning for 28 days of the year.  So if you only do a few contests and nothing else, this could be enough for you, provided your tower is down at all other times.  But for most, it's not enough.

And no, putting your antenna tower on a trailer does not allow you to escape planning if you use it permanently erected at home.  This case should put any 'pub opinions' to the contrary to rest, and provide ample evidence that prejudice against ham radio is very much alive and well.

There are permitted development rights in the UK that allow certain sizes and designs of structure to be installed without permission.  Sadly, the RSGB and the community in general have failed to lobby successfully for such rights in favour of amateur radio.  In short, the law should not make hams have to jump through more hoops to enjoy something that is an accepted part of modern life and a legitimate, educational pursuit.  But the policy makers have decided this isn't the way to go, so we are often forced to go underground to get anything like a half-decent antenna up in the air on our own property.

I agree with the RSGB article that the four year rule is your friend in many circumstances.  However, it can be a friendship hard to make, not least because it could lead the unwary into very expensive assumptions about what they will and will not 'get away' with in reality.  And four years is, in reality, quite a long time for nosy neighbours to stop themselves popping down the local council to moan.

So, what happens after four years has passed and your antenna has gone without complaint?  Crucially, the law states that "no enforcement action shall be taken" after this period.  See guidance here.  In very serious cases, which are very unlikely to apply to amateur radio installations, other legislation can be brought to bear to remove a structure, but in these cases, you must be compensated in full.

So, after four years, your unapproved structure will, in effect, become lawful on the basis that planning law can no longer be used to bring it down.  But you must have put it up in the open, without trying to hide it such that nobody knows it's there until you remove the covers, so to speak.  The classic and definitive recent case here related to the building of a house hidden behind a screen of hay bales.  The owner failed to win the case because he went against the very old legal principle that you must act openly and without hiding something to benefit from a developed right.  Obscuration by an existing structure such as a house, or by trees etc is very unlikely, bordering on certain not to meet the definition of 'hiding' anything deliberately.


You can apply for a certificate of lawfulness, presenting your case that it's been up for four years or more without complaint. In all likelihood, they will want evidence of this.  Typically, a council will go away and leave you alone if your neighbour makes a sworn statement on paper that your antennas have been up for at least four years.  Photos also help, but are not always definitive unless you include something that changes over time - more on that later.

Keep also in mind that three years and a few months might be enough for you to be left alone.  That's because legal processes are usually extremely slow, and it will take a long time to organise a case.  At this point, a council may decide there is little practical point in pursuing the matter, and may leave it there.  Some councils have 3.5 years as a practical working period for determining whether or not to pursue enforcement, but it's not universal. 

If you have managed to have a tower or other structure up for four years without a moan, I would personally never bring it up with a council, or apply for a certificate, simply because they seem to like launching into a fight, often fail to follow procedures, and refuse to properly consider the evidence.

There are many things to take into account if you are going to just stick something up without planning permission.  Firstly, if you live on a remote farm and maybe have some obscuring trees, then the chances are that nobody from the neighbourhood or the council will ever get a chance to see what you have.   But do remember that councils sometimes undertake aerial surveys for planning breaches, although these do tend to concentrate on holidays parks and such like.  I know, because I've worked on many surveys like that.  Antennas, even on the scale of HF beams, are not very evident from the air unless the sun catches them.

If you live somewhere like this (this place is not involved in any planning breach) where people don't go, then you are better placed to benefit from four years of peace to avoid planning rules.  But aerial planning surveys do take place!

In practice, I would expect people living out of sight of much of the surroundings to get away with just about anything in terms of planning.  Even so, it might be better to get a retractable or tiltable mast so that you can make it less obvious at times (and more easily service things!)  Provided you take plenty of photos when it is up, it will be very difficult if not impossible for the authority to prove it was not always up.  You are allowed to bring it down for maintenance without negating your claim for being up permanently, so you can always rely on the 'yes, but at the moment of that photo you took from the air, I was maintaining it, guv.'  Silly, but we are talking about a legal process, so evidence both ways does matter.

Photographic evidence is a good friend when it comes to the four year rule.  Normally, British justice requires the complainant to prove his case.  In practice, with issues like planning, it's up to the defendant to prove that what he claims - his stuff's been there for too long for any enforcement - is true.  That's why photos are essential and, in reality, one of the few sure means of showing the passage of time.  It also covers the possibility of your neighbours being perfectly OK with you antennas, but not wanting to sign any formal paperwork to support you, especially if others are against you.

If your antennas have not been up for four years, make life harder for planners and others by going to your property on 'Google Street View' and ensuring every last piece of the images is objected to on the grounds of privacy and/or security.  Google will then, after a time, blur your house.  You have to be quite persistent, because you will find other angles need to be objected to before the whole thing becomes blurred properly. It is still possible, though, that the council's licence to use Google Earth will permit them to see your house without the blurring.   If your antennas really have been up for four years and Google Earth proves it, then of course, you don't want to blur your house at all!  In many cases, Google Earth images are several years old - often more than four years - so an authority may not be able to rely on this resource to prove their case.

The RSGB advises you to date your antenna photos.  I would go much further.  Use something in the photo itself that changes over time and cannot reasonably be faked.  I used to stick my children in every photo including an antenna, because they change noticeably over a short period of time.  Such historical photos of children have successfully been used in planning appeal cases, so they are of proven worth.  Other things that change are manifold, but hedges, trees, the seasons (was it obviously winter or summer when you took the shot?), your cars (including their legible registration plate) and so on are all things that change more quickly than you think and that often have documents (scrapping and sale receipts, etc).  Include as many as you can, and don't just take a photo of the antenna and tower - that doesn't allow you to put it in a context in time or space!  If you ordered concrete to make a base, keep the receipt safely as evidence, together with datable images of it being poured.

If you get a 'friendly' visit,it may be time to negotiate.


Now, if you get a planning officer coming round for a supposedly friendly chat, someone, somewhere, will have made a complaint.  Councils are invariably too busy to roam the countryside, looking for every minor planning breach.  Guidance from government directs councils to use enforcement only as a last resort.  This is because enforcement is expensive and time-consuming.  If you have your antennas up all the time, maybe you can compromise and bring them down when not in use.  Maybe you can lower the tower.  Or even tilt it over.  Maybe the tower is only marginally higher than, say, the 4.5m or so allowed for other structures, and make the case to the council that it's not really worth getting into a froth about.

In the end, and whilst there will be awkward planners sometimes, most will just want to have a nice afternoon out and get rid of another potential source of work.  They have as much interest in not getting bogged-down in enforcement as you do, so bring out the tea and biscuits, and talk. 

You might even be tempted to go and ask your planning department for advice on antennas.  My advice?  Don't bother.  In most cases, planning officers haven't got a clue about antennas, are generally hostile to them (as are councillors), often because they link them to other things with masts like mobile phone towers and wind turbines!  You will only serve to make yourself known to them, with the fairly remote but possible outcome that some form of 'keeping an eye' on you will then take place.  If you think you have no option but to run the gauntlet of the full process, then of course that is the best thing to do.
If you live next to others, this kind of thing is almost inevitable - as is a complaint to the council.


If you live amongst hundreds of others, it's inevitable that you will come across those who are hell-bent on stopping anyone else doing anything like living their lives in a variety of different ways.  I recently came across a case where a local council had refused planning permission for a SteppIR beam because it chose to believe a crazy old woman's view that such an antenna needed to be approved, which she contended it was not, and that it ought to be erected on an RAF base, not in the community.  The council's own prejudices allowed them to accept such improper arguments, which ought never have been taken into consideration, let alone used as the basis for refusal.  I spoke to the local council about this, and it became clear that prejudices against the applicant played a major part in the refusal.  Again, this should not occur, but is often the result of local people who know one another being given power over others.

So, in the urban world, tread carefully.  Maybe spend a year or more putting up temporary fishing poles for simple verticals or loops.  See how it goes with the neighbours.  If it looks quiet, and there's no RFI, you may want to get a small, retractable mast with an antenna that reasonably fulfils your beaming dreams.  The critical thing, I think, is to hide it as much as possible, and always have in mind that you may have to bring it down altogether at some point.  That way, you won't spend stupid amounts of money on something that you may not be able to keep in the end.

On the other hand, if you put up a one element dipole, leave it there for four years, escape the planning requirement and then proudly go down the street, you'll find you won't be able to get away with putting up a bigger beam - you are claiming four years for what you have had up for four years, not what you wished you had!  However, there is room to argue in this situation that it is the tower/support that is the key planning issue, not the antenna itself.  That's because the test is whether a structure was "substantially complete" four years ago.  It's also difficult for people to tell the difference between a 3-element beam for 12m, and one for 15m, say.  So if you are 'upsizing', it could go unnoticed or be pointless to raise as a planning enforcement issue..

In a tolerant world, hams would have it much easier.  People don't have to go nuts when they see an antenna - we have become accustomed to antennas for over 100 years in the amateur world.  Unfortunately, the words 'mast' and 'electromagnetic radiation' have become synonymous with mobile phone masts which, until recently, caused mass hysteria whenever one went up.  The phone companies got around that stuff by getting a clause where they only have to notify authorities, not get permission from them about phone masts.  Interestingly, nobody seems to protest about phone masts any more.

An argument can be made - supported by some state lawyers, that wire dipoles do not constitute development - and so do not require planning permission.  But tread carefully and know your law!
 
One interesting snippet is that wire antennas were considered, when I asked Welsh Government lawyers, not to constitute development as conceived by planning law.  The basis of that view is quite long-winded, but I have looked at it myself and I can see where they are coming from quite easily.  Convincing your local planning officer about this, however, will be a much harder task!  An area of weakness in the argument is that wires may not need permission, but their supports probably do.  So try to use trees or existing supports to avoid this problem!

If you do run into trouble, certainly get in touch with the RSGB immediately - that is one of the benefits of membership.

UPDATE: 

Since 2009, a 'Harm Assessment' has been brought into force for dealing with alleged planning breaches by some, but certainly not all planning authorities.  Although this is not a licence to put up anything you like, it does provide clarity on how a breach will be dealt with, and importantly, it does not inevitably lead to any further action against you.  Its real aim is to quickly filter-out serious, as opposed to minor breaches that aren't particularly blighting an area, and avoid councils wasting money on pursuing things that would, if you applied, get planning permission anyway.  This approach has always been there in some form or another, but it's now more at the forefront of enforcement processes.

Like any such policy, there is always wriggle room.  The case officer can make a personal judgement as to whether, if you did apply for permission, you would get unconditional permission.  It's the unconditional bit that leaves amateurs less at benefit from this system than otherwise would be the case.  In many situations, there would likely be a condition of how often you can use the mast, how high it can be, what size antenna, etc, etc.  The more jobsworthy planning authorities will always find a reason why it would be a conditional and not unconditional approval, so justifying further enforcement action.  And it is, ultimately, a personal, subjective judgement, which you will find impossible to challenge unless somehow and obviously perverse.

Here is a copy of the policy, noting that not all authorities may apply it very well - or at all.  But you may want to ask for a formal response as to why one council uses this approach when others don't, mindful that the planning laws are meant to apply across England and Wales equally. 

I think councils are stretching their remit improperly when they threaten the spectre of "problems selling your house" without planning for an antenna.  Firstly, if you pull an unauthorised tower down before you sell, there's no problem to fall foul of!  Secondly, if it's been there for over four years and the Council never came round in all that time, it's to every practical purpose lawful and if you applied for a certificate of lawfulness, with good evidence of it being there for that period, then you'd invariably be given it with no further problem.  Personally, I wouldn't bother involving a planning authority for a certificate.  Read on for the best and cheapest way to proceed (not that this is in any sense advice, just information). 

You can buy a very cheap (about £40-£50) indemnity for your prospective purchasers if they query your antenna's (or anything else's) lawfulness, and from plenty of personal experience, know the offer of this will satisfy almost any lawyer acting on behalf of purchasers.  So, whilst councils may want to try and frighten you, it's best not to blink, knowing that it's in fact very unlikely you'll have any problems selling your house at all (the last time I had such minor problems, I sold the house for more than its asking price!)  Remember also that the presence of a tower can often increase the value of your house; there are many hams who sell their properties to other hams, who are often so obsessed with the hobby that they will pay handsomely for a ready-made radio station with planning permission or an installation that is lawful through the four year rule.

It's also become clear that some planning officers ask the home owner whether they have a licence to operate the radio.  That really isn't a matter for them, but OFCOM.  You may choose simply to say 'yes' if asked, but I would certainly also point out that licencing matters - and breaches - are not proper enforcement matters for any local council.  The same goes for health and safety issues that they often want to raise - planning law and appeal cases are very clear that these are not normally matters for planners.

Here's a useful summary from a solicitor specialising in planning law, although the advice does not tell the reader, as I think might be reasonable to do, that a simple and pocket-money insurance policy will get you out of any house-selling fix relating to most planning issues.  In the event that your stuff has been up for four years and the council don't seem able or likely to prove otherwise, or better still, that you can robustly show it has been up that long, there is, in the end, no legal need for you to have a planning certificate at all.

And if it all seems like too much, remember that a vertical antenna, or even a vertical beam, can often attract much less attention from neighbours and planners than horizontal yagis on big towers.  They also often put out better low angle DX signals.  Towers are expensive to buy, and become a bit of a burden for maintenance, insurance, etc.  There is certainly plenty of room to play radio without involving towers - or stubborn planning authorities!











Tuesday 15 January 2013

Delta Loop vs. End Fed Shoot-Out (Updated)

Yes folks, it's time for a (semi-scientific) antenna shoot-out in the Wild West of Wales!



The contenders for the 20m short-out are:

Antenna 1:  A homebrew delta loop, corner fed (vertical polarisation), made of kevlar reinforced wire and connected via 15m of RG213 coax to a G-Whip 4:1 balun.  Apex height 8m, base wire at 1.8m, antenna at right angles (peak gain) to the E-W line.  Total cost: wire £22, balun £45 = £67.


Antenna 2: A G-Whip end-fed half wave, also of kevlar reinforced wire connected to a matching unit via 15m of RG58 coax.  Mounted as a 45 degree sloper to the west from 8m to 1.5m above ground, feed point at lower end.  RRP: £69.

A stranger at the edge of town - a figure-of-eight small copper loop also enters into the fight later on.

8m was chosen as a maximum height because it is about the most you can get out of 10m fishing poles that are likely to be used whilst also being able to support any weight or take any strain.  

Firstly, there is obviously an immediate, if slight disadvantage to the EFHW, because it's connected using bog-standard, cheap coax that has higher losses than the RG213, but only by about 0.5 - 0.75dB, if you believe standard published charts.

How did they do?

Firstly, my subjective assessement, aided by the 'S' meter, was firmly that the EFHW came in significantly weaker on receive by 1-2 'S' units, or 6-12dB if my meter is anything to go by.  Ignoring the meter, I could hear very weak stations to the point of definite readability on the delta, but only knew the station was there and could not make out what was being said on the EFHW.  I did not have time to run lots of transmit cycles, so I can't say anything about that, but from this location at this moment, the EFHW  was easily weaker, and significantly so, than the delta on receive.

Then, I ran some quick WSPR tests over a period of about an hour between 07:00 and 08:00UT.  I chose a brief period, switching for 10 minute periods between each antenna, to lessen the effects of transient propagation effects and progressive changes as the sun climbed in the morning sky.

This revealed a rather more complex picture.  Prior to the onset of LP propagation, both the delta and the EFHW were getting out in physical terms to much the same kind of distance, to Israel or thereabouts from Wales.  Signal comparisons were, as received at 4X1RF (in a direction away from the EFHW's slope and peak gain)

Delta loop: mean of -10.8dB (+\- 2.6dB)      EFHW: mean of -23.5dB (+/-0.7dB)

For ZL4VV on long path, where signal attenuation is vastly reduced compared to other paths, the difference was hugely less, and well within the QSB variations, although I could only obtain one reading due to lack of time to do any more:

Delta loop: -20dB     EFHW: -22dB

Now, don't read too much into those numbers.  WSPR is a weak signal mode that involves miniscule signal strengths that could never be heard by a human.  All you should really take away from the WSPR test is that the EFHW is weaker than the delta, but seems to be comparable to a delta on long path, but that there are discernible differences in signals using CW and SSB on some paths.  The earlier SSB receive-only test confirms this semi-subjective, semi-objective assessment as the delta being the clear winner.  Given the delta has a large capture area, this is hardly surprising.

Going Loopy!

Now, we may forgive the EFHW for not getting across as well as a wave-catching delta loop.  But can we be so forgiving when it fails to do as well as a tiny copper double loop antenna?  My colleague G3JKF is a keen and careful antenna experimenter using WSPR data to guide his design.  I ran the EFHW against Ken's double loop during a stormy night in January 2013 and the following morning, when it was just as windy.  Ken's loop, mounted low on a fence post, with a flower pot to cover the capacitor, and which would stand up to any hurricane with ease, was consistently beating the EFHW on both short and long paths.  You can find details of a similar kind of loop here.

So that I can't be accused of not presenting any data, it's all there for you to see on the WSPR spot database, but here is a random selection from around 10-11:00UT on 27/01/2013, with the EFHW sloping to the west. 

To R4HAC - EFHW -22dB, G3JKF loop: -11dB
To OH5CW - EFHW: -8dB, G3JKF loop: +3dB 
To VK5ZTS - EFHW: -26dB, G3JKF loop: -22dB
To IK2RFI - EFHW: -26dB, G3JKF loop: -4dB

To W4AC - EFHW: no signal received, G3JKF loop: -20dB 

I was going to highlight the fact that the EFHW is just a single wire, very easy to put up in a hurry, and can use trees or similar to prop up the upper end.  But then, a delta is not much more complex, and I have put one up in a howling gale on a beach and in the surf in a few minutes.  And whilst building and tuning a small magnetic loop is not very easy for the uninitiated, it's obviously infinitely easier to mount and poses few problems in transport even if you are on a bike!

Also of importance to the very many of us who live in cramped surroundings is that an end-fed can be put up and pulled down on a fishing pole in seconds and is a very easy, practical way to get an efficient antenna (about 90%) on the go.  Planners and neighbours would have to be especially persistent and unreasonable to object to an antenna of this nature.  But again, the small loop wins hands down when it comes to these matters; due to its size, it will probably escape most people's notice, won't be recognised as an antenna by many, and it almost certainly wouldn't ever form the subject of any planning enforcement.








Saturday 5 January 2013

A Homebrew RF Detector For Pennies - Hat Tip AD5X

Like many amateur radio operators, I'm always interested to learn more about antennas.

For some time, I've been wondering what happens when I send a signal down to my lower corner-fed, vertically polarised delta loop for 20m.  Does it, in fact, radiate vertical waves?  What is the pattern of the radiation?  How true are those internet claims that say corner feeding is 'bad' compared to a 1/4 wave down from the apex? 

Sadly, I'm not an electronics whizz, so I had to rely on the excellent, clear work of AD5X, who has published his circuit online, but is intermittently unavailable.  Luckily, an interrogation of the web archive pulled up the document so you can see a copy below, which is reproduced with Phil, AD5X's permission (6/1/12).  The wiring schematic is fine, but the list of parts omits the capacitor, so make sure you include that!  Also, given the ubiquity of high-intensity LEDs in hand torches, garden solar lights and so on, you'll probably find plenty lying around in broken products that you can recycle.
RF Detector RevA

I spent 30 minutes putting this thing together after sourcing all the materials on e-bay for about £10 altogether.  Even for an electronics ignoramus like me, this very simple box of tricks worked the first time I took it out, and it's surprisingly sensitive - it picks up RF from a 5W input from at least 20 metres away, and a stronger input is obviously detectable from a much greater distance than that - very useful for radiation pattern determination.

On the first night of testing, the little LED lit up to show me where the RF was going.  In keeping with a subjective assessment of the antenna's outstanding performance on SSB and PSK, and an assessment using WSPR, I found with the RF detector that the radiation is strong even at very low angles indeed.  What's more, holding the detecting antennas horizontally revealed only the merest weak hint of horizontal waves in certain locations, and holding them vertically showed a beautifully strong, omnidirectional vertical field - all very much in keeping with modelling.

Heavily metal-laden ground at my QTH makes it very difficult, but interesting to model antenna performance.

So, corner feeding cannot, on the evidence of contacts made and now the RF detector, be consequentially deleterious to the vertical radiation, because the field is physically shown to contain essentially no horizontal component.  Models with a 1/4-wave-down-from-apex-feed arrangement shows an identical, weak horizontal element to the field, at about -27dB.  If I move my detector about 2 m from the antenna, that horizontal component is not detectable, so that's nicely in agreement with the numerical value.

But unlike the model, the LED lights up strongly at slightly negative angles - about 4 degrees - to the base wire of the delta loop (we live on a ridge about 65m above the surroundings).  I have since replaced the LED with a 50uA FSD ammeter, to give at least a relative numerical indication of field strength, if one can see the meter when the box is held aloft.  A pot is also required to adjust the amazing sensitivity of the circuit.