Thursday, 20 September 2018

GB2VK - Marconi Centennial,1918-2018.

This weekend is an incredibly momentous one for Wales, which I deliberately set apart from the rest of the UK because it's not often our forgotten nation gets to take credit for anything!
GB2VK finalising set-up in very inclement conditions, 21/09/2018.

On Sunday, 22nd September, GB2VK will commemorate the 100th year since the first direct, non-relay contact was made between the UK and Australia.

Of course, even a radio message sent from Wales had to be changed to 'England'!

Even at solar minimum these days, we can easily make some form of contact with VK using just millwatts of output.  Back in 1918, when even producing radio waves of sufficient frequency for long distance contact was difficult due to mechanical limitations, it took the Cefn Du (meaning 'black hill) transmitter, a few miles to the north of Caernarfon, a staggering 160kW at LW frequencies to make the VK contact!

The transmitter at Cefn Du, lying at 1000 feet (300m) above sea level on a gentle mountainside overlooking the Irish Sea, was keyed remotely from Tywyn, a tiny settlement 60km to the south.

The antenna at Cefn Du was an enormous inverted-L of some 1100m in total length.  Operating frequencies were experimental, and varied typically between 50 and 100kHz.  With so much power feeding the antennas, local people claimed that steam could sometimes be seen rising in winter from the boggy ground during transmissions!
 
One of the ten, 400ft (122m) tall steel antenna support masts.
The Cefn Du transmitter site, Wales in 2017.  Still largely as it was in 1918, minus the equipment!
One of the many massive concrete stay cable anchors at Cefn Du, 2017.
Concrete base and bolt anchors for a steel tube antenna support, 2017.

Remarkably, after 100 years, the stay cables and huge ceramic egg insulators are still present, lying where they fell when they were cut down in 1939.

John Parry, a former Navy radio operator and, later, university electronics technician, working CW on Marconi Day, 2017.

One of the rooms at Cefn Du transmitting site.  Now in use to stable horses.
The messages sent between Wales and Wahroonga in 1918 was a politically-motivated note of mutual appreciation for each nation's part in the Great War, support for which was waning in Australia at the time.  The war was to end just a few weeks later.

The messages were:

1          1.15pm Sydney time.
            "I have just returned from a visit to the battlefields where the glorious valour and dash of the Australian troops saved Amiens and forced back the legions of the enemy, filled with greater admiration than ever for these glorious men and more convinced than ever that it is the duty of their fellow-citizens to keep these magnificent battalions up to their full strength. W.M. Hughes, Prime Minister."
2          1.25pm Sydney time.
            "Royal Australian Navy is magnificently bearing its part in the great struggle. Spirit of sailors and soldiers alike is beyond praise. Recent hard fighting brilliantly successful but makes reinforcements imperative. Australia hardly realises the wonderful reputation which our men have won. Every effort being constantly made here to dispose of Australia's surplus products. Joseph Cook, Minister for Navy."


The event, taking place in a very rural, quite remote area of Wales, was of enormous interest to schoolchildren at the time, finding themselves living near to the very latest technological advances in communication.

Statue of Mercury, commemorating the 1918 contact, in Australia.



Wednesday, 19 September 2018

Service suspended.

Yes folks,the UK hurricane season has started in earnest!

Although technically we don't get hurricanes in the UK, the wind speeds we experience are of hurricane strength.

Eleven months ago, we experienced one of the worst storms in recent years, ex-Hurricane Ophelia, which seems to have begun a trend of tropical storms that turn northwards towards the UK, rather than running west towards the Caribbean, as is more usual.

Storm Ali, 19/09/2018.

Yesterday (20/9/2018), we saw ex-hurricane Helene swing by, bringing gusts of about 90km/h. A typical windy autumn day in Wales.

This morning, the centre of Storm Ali is running up towards Northern Ireland and Scotland, with winds here in Wales already up at about 120km/h in gusts.
Force 11, and rising...

Although all the antennas remain flying in these conditions, operating during these winds isn't very well advised.

Normal service will resume later in the day.  Maybe...

Saturday, 15 September 2018

FT8 Call.

As a piece of software in development, FT8 Call is constantly undergoing frequent changes and updates.

I was prompted to look at FT8 Call again yesterday, having left it alone for some time due to the lack of users.  Most signals on there seem to be US-based, with few from anywhere else.

Much as I like the USA, I've long ago become tired of the bias in QSOs with that country.  These days, I've returned more to my original interest of working to the east.

The latest FT8 Call user interface is very nice and uncluttered.  There are still not many users, though.

But whilst I sent out a few test calls and beacon transmissions, a slight problem with FT8 Call struck me.

Unlike modes like ROS and OLIVIA, FT8 Call transmits with what appears to be a much higher duty cycle.  Whilst modern rigs are not exactly taxed by running hot, it is something to try and avoid where possible.  It's also regrettable that the de facto operating frequency simply juts into that conventionally used for JT9.

Some ROS operating earlier today.  Great weak signal chat mode, but very few users now.
Perhaps the best mode in terms of duty cycle is HELL, which has reasonable weak signal capability, though nowhere near as good as OLIVIA.  You can send HELL all day, and the rig will not break out a sweat.  But these modes also suffer now from very few users, which has become much worse since FT8 swept in from the west.

Certainly, FT8 Call has some potential.  I'm not persuaded yet, with its very slow transmission rate (a couple of lines takes over two minutes to send in several 15-second 'overs' that split the message into chunks) that it offers much over and above PSK, which we can run at various speeds, according to conditions.  Certainly, I strongly prefer the much more human-centric nature of OLIVIA, HELL and the rest.  You can comfortably type in some free messages and have plenty of time to correct any mistakes.

After writing most of this post, I came across a characteristically interesting video from OH8STN, using FT8 Call to send 'critical', brief update messages from his field operations.  Whilst I do tend to cringe a little bit about ham radio being described as some form of military or emergency platform, Julian has a point in that very quick messages are usefully sent using FT8 Call.

Overall, FT8 call has to show me something more than just the fact that it's new to persuade me to use it.  I'll keep an interested eye over developments, but I think other modes have offered much better solutions, and for some years by now.

Tuesday, 11 September 2018

Hurricane Florence - and radio silence?

Yes folks, despite The Donald's energetic denial of climate change, Hurricane Florence - the most powerful storm ever to hit the US east coast - is already causing the evacuation of at least 1 million people.

Every year, there are people whose sole purpose it is in life to portray ham radio as something that makes a real difference to lots of people in an emergency.
Get out your radios!  Or, just run... Image: NASA.

Every day, there are Maritime Networks and such stuff that endlessly call out for messages from boats out at sea.  Pretty much all the time, nobody does actually call in, not least because there are so many other simple, automated and effective position-relaying systems available at modest cost, and even keep working when they fall into the sea - unlike a HF rig!

With recent earthquake events, there have been the rather ridiculous situations where somebody with not much brain in the USA decides with some friends to try and keep the very middle of 14MHz clear of ham traffic 'in case' someone in Nepal wants some help.  So it continues for days or weeks on end, helping nobody except those desperate people who adhere to this ludicrous vision of ham radio's purpose.

Rather oddly, though, QRZ.com and the usual ham outlets are not (yet) full of EMCOMM people with fluorescent jackets claiming that they will save the world with their 2m FM rig, even though the extent of devastation is clearly going to be enormous.  And there is plenty more action forming out at sea, as I write.

We'll see how many people EMCOMM saves this time.  My prediction is: nobody at all.

But if you really want to know how radio will overcome your lack of health insurance, have a dull few minutes looking at this video:
Hurricane Alley today.  Image: earth.nullschool.net

Monday, 10 September 2018

Magnetic loop: 'real' QSOs at the beach.

A couple of weeks ago, when it was much warmer, I took my car-portable magnetic loop down to the north coast of Anglesey for some WSPR tests.

Whilst I've done plenty of testing of magloops from home as well - showing extremely good results in comparison to full-sized wire antennas - there are always naysayers who claim that WSPR is, somehow, not a meaningful test of an antenna.

This claim is, of course, ignorant nonsense.  It is a plain refusal to accept objective evidence.  If my magnetic loop is better or equal to a full-sized wire antenna using WSPR, then, say the critics, it won't be better for 'real' QSOs, using other modes.

This silly reasoning also ignores the rather important fact that two-way contacts using WSPR mode actually qualify under the LoTW DXCC system.

Well, setting aside those stupid lines of argument, I wanted anyway to see how well my magloop - now kitted-out with a cheap homebrew remote tuning system - performed at the beach.
Cheap, simple remote magloop tuning (needs a longer cable!)

The brief answer is: extremely well!  Despite being too close to the car owing to a short remote control cable, I still managed to get the matching down to 1.3:1, the homebrew control working at a very fine, stable level towards resonance.
Magloop vertical pattern with seawater constants.  +3.1dBi peak gain at very low angles.

I made a contact (at 20W) with JA5QJD at -14dB SNR both ways on FT8.  I then managed to QSO with JA4LKB, giving him-04 and he giving me a less impressive -19dB SNR.

A magloop is definitely not a 'dummy load'!
I managed an EW station, a SV station and a few other European QSOs.  As usual, and with good propagation in effect, the main trouble in operating FT8 is finding a clear spot on the band where others are not transmitting over or very near to you.  This does make antenna performance assessment, especially at lower power, quite tricky.

Unfortunately, the tide was coming in rather quickly mid-morning, so I couldn't spend too much time testing things out further, as the higher one goes up the beach, the closer one gets to where most people park their cars, which magloops don't like much!

My magloop, aiming its vertically-polarised radiation to the NE horizon on a rather dull autumn morning.
The overall experience of operating the magloop, as compared to my vertical mobile stick antenna is that it is at least equal in performance, though I need a much longer period of testing to reach a firm conclusion. 

Certainly, looking out of the car window at a small copper tube loop making a connection between Wales and Japan at 9500km is a remarkable feeling!

Of course, for car-based operating, one might say a wind-resistant stick on top of the car, with no trailing cables to trip-up passing walkers, and no need to tune the antenna up or stop the whole antenna blowing over, is a much more convenient, rapid set-up proposition.  I would have to agree, whilst also noting that the loop, unlike the monoband stick, can be easily retuned anywhere from 7MHz to 14MHz.

But what this test shows is that a magloop is a very effective, efficient multiband antenna that, for those with little space but a reasonably good physical environment, offers a practical, ground-independent option.

Oh, and note that I never - ever - use a 'Faraday' (primary) loop feed system.  This is because that feed mechanism is not very mechanically (and thus electrically) stable, and usually much harder to achieve a good match.  Instead, I use a 4:1 balun, one side connected to the lower centre tube, and the other side connected to an insulated wire running parallel with and close to one side of the loop, where the wire is soldered about 2/3 the way up a vertical side.  If you make the last image full-size, it's easy to see the detail.  I consistently achieve 1.05:1 SWR or better with my loop.





Saturday, 8 September 2018

Horizon hugging.

I was idly looking at the ITUHFPROP propagation prediction pages this morning, although I don't really know why, as the forecasts are often way out.

Still, I noticed that there is a 'Takeoff Angle' calculator that looked like it might be worth a look.

In essence, the software looks at the path, selectable between short or longpath between stations, and produces graphs predicting the most likely takeoff angle involved.

I think the page requires a bit of clarification, because it's not clear who's takeoff angle it is actually providing, though I assume it's that relevant to the transmitting site.

Also, ITUHFPROP is not very useful for lacking any vertical antenna options.  The alternative, PROPPY site is much better in this regard.

Here is the ITUHFPROP prediction for propagation between a middle-distance, run-of-the-mill path between Wales and Greece, showing how the angle changes during the day, though it never reaches very low angles:

Now look at the angle necessary for a Wales-Japan (short) path.  Note that the graphs do not have the same vertical scaling:


This is a path needing a constant takeoff angle of about 3.5 degrees.  To get a feel for what that looks like in reality, take a sea horizon and hold out two fingers horizontally together at arm's length.  That's roughly 3 degrees; it's a very low angle that most people cannot access.

For a Wales-Japan long path route, the necessary angle is even lower - just under 2 degrees. 

That's where a super-clear, super-ground location at the beach is such a wonderful place to play radio, and why a vertical antenna is a great help to achieve those low angles.

What stations await beyond?

A modelled (in this case, 7MHz) quarter wave vertical with seawater ground constants.  Peak (and good) gain in just the right place for long-haul DX!


Friday, 7 September 2018

Remote magloop capacitor tuning - a simple approach.

2018 for me has been the year of getting many little, unfinished projects completed at long last.

One of the longest-running campaigns has been to get a remote-controlled, motorised capacitor tuning for my various magloop experiments.

There have been moments when I felt like simply buying a commercial loop.   The very high cost of these loops (about £1200) could be offset with the mindset that you only ever buy a good magloop once.  But the problem for me is the likelihood for the proprietary loop tuning unit electronics failing, and proving to be difficult and/or expensive to repair.  I am not an electronics expert, at all!

It would therefore be silly to spend that much money simply to get a tuning unit that will inevitably fail at some point.  A magloop itself, despite the rubbish people write about them, are always a very easy thing to build to high quality, costing maybe £25 in new copper tube.

I've approached the problem in my usual way: what readily-available materials can be used to achieve cheap, effective and easily replaced or repaired tuning? 

The final protoype version appears below.  Of course the wiring hasn't been tidied up yet, but that is just a cosmetic thing.
Cheap tuning...

In brief, you take a 12V DC input into a DPDT switch that acts as the forward/reverse control.  Then the feed from this goes into (in my case) a discarded potentiometer, providing speed control.  One line from the output of that goes through a momentary push switch, which provides fine 'pulse' control as best match is approached.

The motor is a 3rpm unit from China, which is connected to a Delrin isolating rod via a semi-flexible reducing coupler (the motor shaft and planetary drive socket is 5mm, everything else is 6mm).  The rod is attached via another semi-flexible coupler to a 6:1 planetary unit. You can find all these things on E-bay.

The capacitor is attached to a plastic base, which is fixed with one screw at the top. This allows it to move a little, to line up properly with the motor couplings, although the alignment is actually already very good.

I tested this in the garden last night.  Using an analyser I could see the simple system works really well, allowing the very fine control needed to tune these extremely high-Q loops without difficulty.  Moreover, it only cost, if you buy everything new, around £20 (couplers are the most expensive things, at about £5 each!)

I have also bought a PWM motor controller for the amazing sum of £3 from China.  This is the best thing I've found in a long time!  It does much the same thing as my own idea, but the pot is much better ranged, and the two momentary buttons give instant, rather than switched direction changes.  As the father of a son with colour blindness, I'm also bound to say it's a shame that control makers continue to make red and green coloured buttons.

DC motor PWM controller.  Great solution for £3, delivered!