Figure-of-Eight Magnetic Loop - WSPR Results.

Last week, I built a 75cm-diameter (per loop) 'Meight', or figure-of-eight magnetic loop, to see how well it would perform compared to other loops I've built.

The comparison antenna, as is usually the case, was that run by GI8YJV in Northern Ireland.  At least at 14MHz, this trapped dipole outperforms just about everybody else in the UK on WSPR, and almost exactly mirrors the performance of my very well-matched, twin-fed vertical delta loop.  The difference in latitude and longitude is also minor.

I also use G8LIK as a comparator, as he is using a large 'Skywire'-type, horizontal loop that also performs very well, albeit with clear signs of having more skyward radiation than low angle.

My homebrew figure--of-eight loop, graced by the Moon at sunrise, 29/10/2018.  Note the feed has now changed (below)

New feed, with wire external to and well away from the loop yields less minor SWR drift in rain.

 
Now, if you are one of those people whose mind is more fixed than flexible, than please do remember that this test is, and is only claimed to be, of a small transmitting loop antenna.  Its virtue lies in being small, works close to the ground, and is either outside planning regulations or very unlikely to warrant enforcement action in most countries.  It can be deployed indoors and on balconies.  This is not a comparison with a Yagi on a 100 foot tower, which is a huge investment of time, effort, money and space.

I have been quite pleasantly surprised with this antenna.  For one thing, it's very easy to build for very little money.  Secondly, it has proven to send out a good signal.  Mounted vertically on a low post (base ~1.5m), the loop was giving the GI8 dipole a good run for its money.   Even better, it consistently outperformed the large wire loop.

I felt the loop was working so well, even getting 200mW at good strength into west coast USA, that I hurriedly mounted it at a better height (base ~2.5m) for more tests.  This did yield a small but detectable increase in performance.  That said, the increase was not such that you would lose out in an appreciable way if you were restricted to using it on a lower, ground-mounted stand (which also has the advantage of being easily turned, for directivity).

So, let's look at about 3 days' worth of WSPR results.

First, the magloop vs. the trapped dipole at GI8YJV:

That's a pretty good result, considering the size of the magloop.  Now let's look at the simultaneous signals beyond 5000km, i.e. DX distances, to see how well each was being received by the same stations, at the same time:

The magloop is 5dB weaker than the trapped dipole.  It's about 6dB worse on local signals, but that's not usually of interest, at least to me.  That is pretty much what we might expect, and translates into just a single 'S' point down on the trapped dipole, if considered in the increasingly-irrelevant tradition of SSB signals.  In digital operating, 5dB is going to see you get through to almost all the places that the trapped dipole gets to, as the map of receiving stations illustrates:

Interestingly, the loop is able to match the dipole at times, even at the extreme DX range, though not necessarily at the same time:

When compared to the large wire loop at G8LIK, the magloop exceeds its performance by a very wide margin, most likely explained almost entirely by the better low angle, vertical radiation from the magloop, as evidenced by the big differences towards the late afternoon and early evening:

I'd like to show you other comparisons, but it's not easy to do.  First, you get a lot of people who only operate WSPR for a few hours, or a day or so.  Then you get people who operate continuously, but are anti-social in not publishing anything at all about their station, or providing a means to contact them to ask!  MX0PHX, a club station using a low, OCFD dipole, is the only other reliable station I can choose.  Whilst only at 4m up, the antenna is at least in an open, rural site.  The magnetic loop compares very favourably with this full-sized wire dipole:

In terms of signal strength at DX distances (set at >5010km), the magloop actually comes in at over 2dB better than the OCFD:

Whilst the 'Meight' loop is taller than a single loop, it is quite rigid, even in 10mm copper pipe.  The second loop adds another point of attachment at the top.  This is how strong this all is in the 100km/h winds of ex-Hurricane Oscar this morning (03/11/18):

One thing you do need to do is make sure that the capacitor and all connections to/from it, including those to the motor, remain dry.  My loop showed a small but definite SWR drift over time, which I eventually realised was caused by water getting in between the capacitor vanes!  Remarkably, this didn't seem to make an enormous amount of difference to the loop performance, though the SWR was far too high.  Sealing the cap housing ensured dryness, and now the SWR drift when it rains is very slight, remaining below 1.4:1.  There is probably more that can be done to prevent stray capacitance in wet weather, but it's not something to worry about at the moment.

All things considered, the 'Meight' is clearly an efficient antenna whose size, convenience and sheer possibility of being deployed when larger antennas may be prohibited, means this is very much worth building, regardless of whether you have a large antenna farm, or a HOA flat.

You can of course buy a 'Meight', which does have the advantage of automatic and manual remote tuning.  But, at £504, that's an expensive tuning circuit!  It's also the case that the commercial version comes delivered to you in sections.  Each connection will involve some loss, especially as they are not soldered, but mechanical compression fittings. 

UPDATE: 19 days of WSPR

All compared to MX0PHX (OCFD at 4m height, in open, rural area).

(1) Simultaneous spots, all distances:

(2) Simultaneous spots, DX distances (>5010km):

(3) DX Graph:

(4) Spots map:

(5) Magloop compared to GI8YJV(top WSPR-performing trapped dipole):

Build instructions for the Figure-of-Eight magnetic loop.

Following a number of requests, here are some simplified instructions for the 'Meight', or figure-of-eight magloop.

This design will work from 13MHz and probably up to about 18MHz, maybe higher, I haven't yet tried it out beyond 14MHz, where the match is 1.1:1.  Efficiency drops as you go down in frequency.  At 14MHz, efficiency will be around 95%.  Remember that there is still active debate about how accurate 'traditional' magloop efficiency formulas actually are.

(1) Buy a roll of 10mm copper microbore tube, the kind often used to plumb central heating radiators.  Alternatively, you can make a square loop array from 15mm copper tubing, except the build is slightly different.

10mm microbore, as usually found in hardware stores.

(2) Assuming we're using 10mm tube, this is quite easily bendable by hand, more so if it's warmed up.  It usually comes in a plastic bag as a coil.  You should be able to open up a decent circle of tube such that the diameter is about 75cm.

(3) Use pipe cutters or a hacksaw to cut two full circles from the roll, each ~75cm in diameter.

(4) You can either solder the tube together using straight couplers, or you can do what I do, for which there are photos.  This is a little tricky, but it does tend to yield quite a stiff loop array that is useful to maintain good matching.

(5) I took two lengths of 15mm copper tube and hammered it between two pieces of wood to make a flat bar.  Clean these very well with wire wool, coarse sandpaper or a rotary tool with sander attachment.  Cleaning is essential, otherwise you won't solder successfully.

(5a) Number 5's method works OK, but effectively makes a plate capacitor.  Even with an insulator (such as wood) between them, the intervening material provides a wettable surface that will allow a water bridge to form, and change the matching of the loop in rain.  You need to either cut the excess copper once it's all be soldered up and support the loop so that there is only a good air gap between the connections, or, preferably, just use soldered straight connectors to make the figure eight, rather than my initial method.

(6) Also clean all four ends of the copper tube rings to at least 2" from the ends.  A good guide to general soldering principles can be found in this video.

(7) Place one end of the bar in a vice or somehow otherwise make sure it's secure and can't move.  Heat the end of the bar with a butane torch strongly, and do not remove the heat (because it will allow contaminating oxides to develop) until you have applied a good amount of solder.  Use a fairly thick gauge, flux-cored solder.  When you are at the right temperature, the solder will run 'thin'.  You can remove the heat now.

(8) Apply heat to the end of the rings and apply a good amount of solder to each end.

(9) Bring the pre-soldered end of one ring to the soldered end of one of the bars and apply heat to both the bar and ring together.  After a short while, you will see the solder run thin again, and you can remove the heat but ensuring the ring and bar remain firmly in contact. You may need or want to add a little extra solder between the elements to make a stronger joint.  Having someone blow on the joint helps shorten the period you have to keep everything still.  REMEMBER THAT COPPER STAYS HOT FOR A LONG TIME AFTER REMOVING THE HEAT!

(10) You should end up with something like this:

The bars provide a way to easily make a figure of eight, and also provide a strap attachment point to wood, etc. BUT SEE NOTE 5(a)

On the left, you see one loop, with the ends offset by a couple inches.  On the right, you have loop two, also offset.  Soldered to the bars like this, they yield a figure of eight.  AGAIN, SEE NOTE 5(a)

This should give a clearer picture of how it goes together. The wine is 2018 Damson.  SEE NOTE 5(a)

(11) As you can see from the photos, you also need to solder either some thick gauge wire (something like Flexweave is OK), or copper/brass braid or shim metal to make the connections to the capacitor.  I solder spade connectors to the ends of these.  Always clean everything with wire wool or an abrasive tool to ensure good quality soldered connections.

(12) I made my own loop mounting stands out of old timber.  You can use a fence post with a piece of 2x1" timber screwed into it for added height, or some other arrangement that provides enough support and resistance to wind.  You can also add guy rope, provided it is not connected to the loop itself (which will lead to stray capacitances and detuning in damp weather).

(13) All you need to do now is add a suitable capacitor.  You need a wide, air-spaced variable of around 10 or 15pF to 275 or 300pF, preferably one that is of the butterfly type that has infinite rotation (i.e. no stops).  If you have one with stops, that's fine, but not so clever if you want to motorise your capacitor later, because you need to incorporate motor stopping switches.  You can also use vaccum capacitors, but these are heavy and fairly expensive.   A suitable capacitor is typically about 3-5 inches in length.  Be careful not to inadvertently buy a heavy, 12" long cap!

(14) It is fairly easy to just tie-wrap (cable tie) an air variable capacitor to a timber or plastic backing of some sort.  I recommend you make it weather tight if possible/necessary.  Sticking it in a plastic drain pipe with a cover is often a good housing.  A vaccum capacitor is more challenging to mount securely.

(15) Once you have soldered connections to the capacitor and secured it on your magloop stand of some sort, you then need to feed the loop.  Most people follow the herd and use a primary, or 'Faraday' loop.  I never use these, because they are often mechanically unstable, and can make it difficult to reach the best match without a lot of shape-bending and moving things around.  It's better to use a 'pseudo-gamma' match, which goes like this:

(a) Take a 4:1 balun.  Attach a short wire from one output to somewhere along the bottom of your lower loop.  Then take an insulated wire that's about the length of one side of one of your loops, and attach this to the other output of your balun.  Wrap the wire around one side of the lower loop, and use a crocodile clip to attach it roughly 3/4 the way up.  Once you find the correct spots to attach the wires, you can (and should!) remove the clips and solder the wires on.

(a1) UPDATE: The above crossed-through method works perfectly fine, but I have found it susceptible to minor but irritating SWR changes during wet weather, as water gathers between the wire and the loop, introducing capacitance changes.  If you look at the third image below, this provides a perfect alternative matching point (~1.09:1) and, at the time of writing, because the entire wire is well outside the loop and not in contact with it as previously, such that water can't accumulate, the SWR drift seems to be eradicated.

General view of the loop array, initial test.

Following day, with soldered connections!

Final iteration - modified feed.

(b) You can now just tune the loop by hand.  This is not easy, due to the very high Q of the antenna, but you will get a feel for it and so it can be done.  You can achieve reasonable tuning accuracy by ear, as the noise will get noticeably louder as you reach resonance.  Then use your rig on low power and a CW or digital tuning signal to test the SWR.  For fixed-frequency use with digital modes like WSPR and FT8, it's easier to use an antenna analyser for a perfect match.  If you can get the 'dip' in the matching to reach your desired frequency of operation, but the SWR is too high, you need to move the feeding wires around a little.  Try moving the base wire from the balun up the side opposite the long wire feed first.  If you have an antenna analyser, you will see the 'dip' get deeper, reaching a more perfect match.

(16) For a simple, remote tuning system, have a read of this earlier blog post and look at the photographs for how the mechanical assembly fits together. 


Here are some early results on 14MHz WSPR, 200mW.

Figure of Eight Magnetic Loop

This week has seen a flurry of yet more magnetic loop experiments, using some spare 10mm microbore copper tube I had in the attic.

I started out with a parallel, double loop array for 20m.  This ran on 14MHz WSPR for a couple of days, and turned out to be a perfectly good performer for its size, simplicity and cost.

Parallel loop array with homebrew remote tuning and pseudo-gamma matching system.

Here's how the simple distance graph looked, when compared against a full-sized dipole that is known to be one of the best on the bands.  Disregard the second day of comparison, because it has been affected adversely by a battery supply that had exhausted:

Parallel, two-loop array at 14MHz.

The smaller bore tube works fine at 14MHz, although some extra height above the ~1.5m base height I used would make a positive difference.

I decided then to recycle the parallel loop array into a figure-of-eight loop.  I've long wanted to build one of these, but never got round to it.  One thing I found with my construction was that the loop, having a bit of a twist at the 'waist', introduces some considerable stiffness to the whole thing.  This makes it very mechanically stable, and so eliminates changes in the tuning due to strong winds.  With an exceptionally high-Q antenna like this, mechanical and electrical stability is essential.

My figure-of-eight loop in 10mm microbore tube.  Plum wine and axe in the kitchen are optional!

The weather is Arctic cold today, with moderate winds direct from the North Pole.  It has remained drier than forecast, though, so I am now active (pm, 26/10/2018) on 14 MHz WSPR.  The matching is extremely good, at 1.05:1 SWR.

Now in action on 14MHz WSPR!

For now, what I can say is that I have, in essence, saved myself almost all the astonishing £502 that the commercial version of this antenna is now selling for!  A useful RadCom write-up, including an EZNEC model, can be found here.  There's no doubt at all that those corrosion-prone compression fittings on the commercial model should be replaced with soldered connections, and reduced in number through using formed pipe. 

IARU Region 1 vs. EURAO (again)

It seems the already fragile relations between EURAO and IARU Region 1 have collapsed once more, this time into open hostility.  The situation is summarised thus by EURAO:

"IARU Region 1 can not be considered a reliable "partner". At least with its current directorate. The quote from John C. Maxwell comes to mind: "When you make a commitment, you build hope. When you keep it, you build trust".

IARU Region 1 has, from the outset, seemed for all the world to be worried and threatened by EURAO.  According to EURAO, about two years ago, IARU R1 representatives, who do not look very happy in any of the photographs that emerge, took to questioning EURAO about what it was up to, but deciding that IARU R1 would not itself be making much comment.

After what was obviously a very terse initial meeting, attempts were made by EURAO to reconcile differences and move forward in a more constructive manner.  At that meeting, IARU R1 representatives almost, but not really convincingly, appeared to smile.

IARU R1 (two centre) flanked by EURAO in (slightly) happier times.

Now, EURAO has decided it has pretty much had enough of IARU R1, and has issued a breathless - and rather difficult (in the translation) to understand - statement on how, in its view, IARU R1 is pushing ahead as the only one, true representative of amateur radio.

If you ever wondered what the hell IARU and its ilk actually do, then you can find a terribly dull recorded presentation that will send you instantly to sleep here.

I can't comment on any of the people involved in either organisation, because I don't know any of them.  But the kind of antagonism claimed against IARU R1 does not very much surprise me, because people invested in sitting on committees and attending meetings like this are very often prone to defending the status quo as they see it.

What none of this antagonism does is help amateur radio.  IARU R1 may well do sterling work, but it has, at least until recently, not been particularly well understood or perhaps sought to make its work known to the common-or-garden operator.  This much is clear from the opening question in the above video, where there is a total confusion of hands going up and down hesitantly in response.

My take on IARU R1 is that is comes across as a dinosaur that has suddenly had its tail shaken by a new organisation in the form of EURAO.  EURAO, though slowly gaining recognition, is finding it somewhat difficult to make progress.  As a result, IARU R1 seems now to want to show all the world how great and relevant it is, and has been all along, just we never realised it.

Certainly, I was interested to look at the video of Don Beattie, and find how much of what he and his lot have managed to achieve does not really seem to make much difference to the real-world experience of the average amateur; solar PV still obliterates HF locally, and LED lights continue to inject RFI directly into the mains supply.  Rules on paper are one thing.  How and whether they are applied at all, is quite another.

There are a lot of issues to get on with in managing the radio spectrum, and we can do without both committee urchin mentality and open warfare between different factions.  That is the kind of division that allows others to more easily get what they want, which is almost always to the detriment of amateur radio.

$1799. Really?

I was interested to learn from one of the very many ham radio sites about the Ciro Mazzoni Stealth Loop recently.

Although I don't need a stealth antenna, I understand many do, and it is anyway always a good idea to think of small, efficient antennas for portable work, no matter how much room one has.

The Mazzoni loops have a very high build quality, and a purpose-built remote tuning circuit.  So the professional construction is not in question.

A very militaristic-looking Stealth Antenna by Mazzoni.

What I do, very much have an issue with, is the price.  In the US, the Stealth loop, essentially a flattened loop of aluminium with a capacitor on top, is now selling for $1799. In the UK, it's more like £1100, i.e. a lot of money.

From lots of experience with loops, this squashed loop design will certainly work.  But practically all its radiation will be in the horizontal plane (note, there are essentially no vertical surfaces).   So the pattern will yield NVIS radiation.

OK, you may be happy talking to a thousand Italians from the UK of a weekend.  But most of us like some good DX.  Digital modes overcome some of the traditional antenna limitations, of course, and no doubt DX will roll in with this antenna.

If you are tempted by this loop, remember you could build something just as efficient and, if you make it less squashed, more so, for a tiny fraction of the $1799 Mazzoni is selling his for.   Whilst the proprietary remote tuning is nice, remember these things can break.  Repairing them is not cheap, and may not be possible in future as components become obsolete.  A simple PWM-driven motor and air spaced capacitor costs pennies and can be replaced without bursting into tears at the cost, and being off air for weeks whilst the circuit is off, being repaired.

Another thing I note in one of the videos about this loop is the matching.  I'm not impressed by a 1.4:1 SWR, and have never seen such a high value with any of my homebrew loops, which are a lot more roughly built than Mazzoni's fine efforts.

In the UK, a normal, non-squashed loop down to about 60m remains within planning control limits, and would anyway very rarely be considered something needing enforcement.  HOA properties in the US are a different case, of course, but I would think a thin wire loop around a balcony would more likely escape attention, and perhaps be more efficient, than a squashed black loop that looks like an automatic weapon!

A visit from the electricity company.

Yesterday, I was out walking when I got a call from a network manager for the electricity distribution company.  I had been expecting to hear from him about land access permissions for maintenance.  Of course, I was at the furthest point from the car when he called, so I had to run 3 kilometres to make it on time back home!

The land access took very little time to sort out, so I ventured to ask the manager about PME mains supplies and RF earth.  So far as I knew, I have complied with the regulations by installing 10 square millimetre conductor from each station RF earth (I have two), back to the distribution panel ('consumer unit') next to the incoming supply.  But I noticed the earth cable from the panel to the incoming (sealed) mains fuse was only 6 sq. mm, which is apparently not something to worry about, because it was there before the current regulations came into being, and so cannot be made retrospectively applicable, plus the likelihood of a fault is not very high.

Now, I've seen a lot of operators who are completely lost as to why they are providing earth for their stations (most, wrongly, think it is something to do with electrical safety), and very many variations on how they do it.  It has even led to a highly embarrassing and quite dangerous situation about a year ago, when the RSGB published an article that did not take PME supplies into account, and did not tell people to check or how to provide the correct earthing system if they had such a supply.  I did advise RadCom about this error, which they accepted, but I never did see a correction published, although they did ask me and others if we would be willing to write such a correction (I am not qualified, so of course, declined!)

The 'virtual' earth in a PME system.  The earth in the house is actually connected to the incoming neutral.

In brief, PME is a rather peculiar system where the neutral line provides the conductor for the earth.  In other words, any accidental break to earth sends the current down the neutral line, to which an earth connection is made every few poles along the line.  There is therefore no separate earth line, except a 'virtually' separate earth line in the property itself.

The problem with PME and RF earths is that, unless you connect each copper rod or tube that provides the RF earth point back to the distribution panel, a neutral break somewhere along the transmission line will see the circuit trying to complete by going down the alternative earth the operator has (for the electrons), usefully provided.  This could see several properties' worth of current trying to do the same thing.

In summary, if this were to happen, your radio equipment may well catch fire and quite easily spread, burning your house down.  Worse, a proper fire investigation would almost certainly identify your now blackened RF earth as the cause, and your insurance may not pay out, because you didn't conform to the regulations.  In the UK, all work to mains supply is now meant to be done by certified electrical installers, so DIY changes that used to be (and still are) common, are always, technically, a breach of the regulations.

Anyway, I was able to confirm that I had done everything correctly, but that there was some uncertainty as to the type of mains supply.  The manager was very helpful and well-informed, so he has offered to come in his spare time to check the supply type in some days, and have more discussions about the network.  I'm only too happy to learn more about these things, and I think the manager is too, because he had not really come across such a situation very often before.

Unfortunately, for legal liability reasons, the manager doesn't give talks on electrical safety, nor does he write articles of the kind that would properly correct the RSGB's efforts, which is a real pity.

Nice backscatter example

Short post: an Italian station called me whilst I was beaming 220 (South America) today.  As I turned my beam to 150, to point at Italy, the signal clearly dropped markedly. 

A nice example of backscatter propagation.

12m: Open to the world!

Yes folks, believe it or not, 12m has been open to far distant places all day long, from just after sunrise to long after sunset.

At 17:56UT, over 30 minutes after sunset, I was still working a LU7 station, together with a load of PU and even a ZD7.  Earlier in the day, a 3B station was again active, and in the afternoon, I worked some K4 stations.

Working Latin America on 12m - even at dusk!

The old texts about bands and solar conditions are now largely junk.  Armed with a good antenna (though many I've worked only have 1/4 wave verticals), digital modes and a little patience, the higher bands are more open than not, even at the very bottom of solar minimum.

I even worked a station or two up on 10m today!

Protect Our Planet From Solar Storms - Zooniverse project

Woodpecker RADAR - on 12m!

This afternoon saw reasonable propagation into the eastern Mediterranean, and also allowed a few signals from well-equipped stations in the US to come through.

As I turned my beam towards Cyprus, 24MHz was suddenly hit by a strong, but QSB-affected woodpecking signal for many minutes.

No doubt, given the Russian's known use of OTH radar, and the beaming direction lying towards Syria, that this was related to some ongoing activity there.

For humanitarian, as well as radio reasons, one hopes the woodpecker will not be singing for much longer.

G1 Storm

Last evening (07-08 October 2018) saw a G1 disturbance of the geomagnetic field.

The only anomalous propagation of my 100mW at 14MHz was to TF1A and EA8BFK, stations lying at 335 and 212 degrees from me as a magnetic heading.

TF1A was hearing until 01:00UT at -17dB SNR, EA8BFK also until 01:00UT, at -12dB SNR. 

Interestingly, TF4M, who lies 189km NNW from TF1A, did not hear me at all after 21:42UT, despite having an extremely good station and location.  Typically, around my local magnetic midnight, TF4M is just underneath or slightly to the north of the inner edge of the auroral oval, whereas TF1A is typically around the middle of the oval.  The longer path through the oval is likely the explanation for my signal failing to get through to TF4M.


It's extremely difficult to correlate the cause of this roughly 90 minute extension in propagation to any of the field components, across any of the northern hemisphere magnetometers. 

TF1A kept hearing my 100mW throughout the very disturbed conditions.  More typically, anomalous spots tend to appear around the point where the field is restoring to quiet levels, and this is what was seen with EA8BFK last night. 

Rough conditions in space!

Yankee Bravo!

Mr. Bas, PE4BAS, inspired me to have a look at 60m again today, thanks to his latest blog post entry.

No sooner had I switched over to 60m WSPR that I was quite pleased to see a YB station appear, though weakly, on the waterfall!  I've been heard in VK before (they were not allowed to transmit at the time), but I think this is the first DX I've heard from that far east.

Antenna tuner

I woke up this morning to extremely heavy rain.  Under these conditions, the resonance of my 20 m vertical delta shifts fairly significantly.  Not enough to require an ATU, but it would be nice to match out the small error when necessary.

The basic lesson of this post is one that many people have issued before: an antenna matching unit is extremely easy and relatively cheap to make.  For example, it's well worth having a look at this clear, simple article by AA5TB.  This site by VK6YSF also very clearly shows the underlying simplicity of a T-match ATU that anyone can copy - even an electronics non-expert like me!

A commercial non-continuous inductor ATU, such as the actually very robust MFJ 941E I've used for many years, costs a shade under £160 in the UK at the moment.  Not a bad investment at all, but it is slightly limited in having only a fixed number of inductor positions from which to choose.

If you want a continuously-variable 'rollercoaster' inductor, then the cost goes up to around £250.

So here is what I threw together as a proof-of-concept prototype this morning, to see if what I had lying around in the junk cupboard could make an effective and, above all, efficient ATU.  The capacitors (one encased in a PVC tube for earlier use on a magloop) typically cost about £10-£20 second hand on E-bay, and a roller coaster inductor, though much rarer, is about £40. 

Origins of a homebrew ATU...

Of course, it looks awful, with all those spade connectors and loose wires.  But it works!  Looking at the WSPR reception reports from IZ0FKE before and after connecting to this rat's nest shows an already increasing signal continued on-trend, and certainly shows no obvious sign of any deterioration due to the introduction of the circuit.  The blue vertical line shows when the ATU was put in-line:

Before and after reports from IZ0FKE.  200mW, 14MHz.

So, even if you have to buy used components for this ATU, it will only come in at around £80-£100, or not more than about 2/3rds the cost of a fairly basic commercial unit, or less than half the cost of a roller-coaster unit.  OK, there's no matching meter, but that's not really necessary, and can be added at a later stage, again for pocket money if you haven't already got the parts.

To the sky, I return.

After about six years of taking a break due to family duties, I have decided to return to the skies and revalidate all my flying licence documents.

After many years of operating amateur radio, and having enjoyed it immensely, it is time to do something a bit more serious again.  If you've ever used radio in aviation, you will understand how ridiculous a lot of the ham operators are in taking hobby radio so very seriously.

Much more rewarding than ham radio, I'm afraid!

The flying fun starts with an eye test and getting some new glasses, in case my eyesight isn't good enough without them.  If they were not, I would probably have to pay for a revisit to the aviation medical examiner.

Then I get a full aviation medical, with electrocardiogram and all the rest.  Then it's paying to revalidate my aviation radiotelephony licence, followed by a conversion of my UK-issued licence to an EASA (EU-wide) one.  Each step, you will realise, costs quite a lot of money!

Time to start filling a different logbook again!

Sadly, operating /AM in the ham bands is not legal in the UK, so I won't be able to offer any interesting calls for your log!

I'll still be operating ham radio, so this blog will keep on throwing out occasional bursts of wisdom, and quite a lot of hot air, too!

Geomagnetic effects, 2018 October 01 - 02

With the advent of the dark months here in Wales, attention is turning to accumulating data on geomagnetic effects on WSPR propagation at 14MHz.

Already, just a few days past the Autumn Equinox, and with very low solar activity, propagation on 14MHz now tends to collapse by around 22UT (W4HOD is typically the last to hear me then).

Yesterday saw some moderately rough geomagnetic conditions. Here is how the Leirvogur magnetometer saw things:

Looking at the database of who had heard me overnight, I could see that only TF1A had done so.  This is how I was heard with time (the blue line at right indicates 00UT):

As you can clearly see, propagation to TF1A from my station had collapsed by quite early in the evening, the last spot timed at 17:56UT.  The ongoing disturbance may well have contributed to the early propagation cessation.  I confirmed TF1A was in fact operating during this period, and had not simply disconnected for a while, by looking at his reception reports for other stations, mostly from EA, as it happens.

Then, shortly after 00UT, TF1A starts hearing me again at quite strong levels, with two peaks of -13dB SNR and -10dB SNR at 00:52UT and 02:32UT, respectively.

If we mark those two peaks on the Icelandic magnetometer output, we can see that they coincide, as I have always found, with the field's 'H' (horizontal intensity) reaching the end of a 'rebound' (restoration) to levels typical of quiet conditions, although the field need not stay quiet for the effect to be realised.

The effect is probably the result of enhanced total electron density after a disturbance.  The link between field restoration and enhanced electron content after an, admittedly, much larger disturbance, was noted in a 1998 paper.

Where WSPR proves very valuable to these studies is in its continuous availability at many locations across the globe, although distribution is very skewed towards industrialised nations.  Even so, there are a good number of stations at high latitudes now, where in the past, studying polar effects required a lot of effort to organise, and typically relied on only a handful of transmitters and receivers operating for just a few hours.