It's been a long day here at Copper Mountain Headquarters! So long, it's nearly eight o'clock that I am writing this.
The reason? Well, that is a long story. It started with my noticing the vertical delta loop was a little higher than usual in SWR during very wet weather. It is usual for the matching to change a little in such weather, but now I was seeing 1.5:1 at 14MHz, and something similar at 28MHz, the first harmonic.
Eventually, I found a break in the wire near the feedpoint. Nothing to complain about after five years or so of swaying around in the wind, often violently.
After repairing that, I applied the SARK analyser to the antenna, to find that, whilst 14MHz was now OK, 28MHz was way off, at about 2.5:1.
This is where things ended up wasting a lot of time. I changed the homebrew 6:1 voltage balun for a commercial current version. I knew this gave a higher resonance point, so I added a length of wire in the centre of the base (radial) wire until the match was very good at around 1.14:1 at 14MHz.
But sadly, 28MHz was still way out, although with a 300Ohm twin feed, this is of essentially no consequence as losses in the line are tiny compared to coax. I just don't like using a tuner.
I then slowly came to realise, as the sun went down, that the original, homebrew balun could have water in it. Any change in antenna characteristics should first cast doubt on any balun in use. If only I remembered this at the time! I had taken a lot of time to make a high quality balun, but had somehow forgotten to put drainage holes in it. I do use watertight boxes and a stone cover, but water always gets in slowly.
I opened the cover of the balun to find - yes, a pool of water in the bottom of the box! Arrrghh! I had wasted all that time matching the antenna to the commercial balun, and now I had to undo all the self-amalgamating tape, remove the long wire and restore the antenna to its original dimensions!
Anyhow, as it went dark, I had everything reconnected, weatherproofed and the balun covered with plastic and a ridge tile. I also drilled small holes in the bottom that let water out, and only the very tiniest insects in!
SARKPlots sweep at 14MHz.
Same vertical delta loop at 28MHz.
The result is that I have, once more, a vertical delta with a 1.2:1 match across essentially the entire 14MHz band. At 28MHz, normal operation, with a SWR lowering across the whole band, is restored.
Last evening, having some time to wait around for family, I went to South Stack on Holy Island, which is part of the EU-124 coastal island groups under IOTA.
Holy Island, part of the wider EU-124 group.
Unfortunately, the IOTA system shows weaknesses with EU-124, in that Holy Island is connected by fixed road and rail infrastructure that renders it, to all practical effects, part of the larger island of Anglesey (which is considered part of the UK mainland, itself a bone of considerable and long-standing contention). Compare that with another EU-124 member, the offshore reef we call 'The Smalls', and that is found to be over 28km out to sea!
The Smalls reef. Getting here is almost impossible for most.
Anyway, I decided to run WSPR around the sunset period. The antenna was not as well matched on this very ancient rocky sea cliff as it is down on the seawater-soaked sand, coming in at around 1.5:1. I sent 1W at 14MHz out of the TS480 in the boot, and then went for a walk.
Sea cliffs at South Stack.
Twenty-two minutes later, I was really quite pleasantly surprised at how well the stick antenna did. To all intents and purposes, it looked on the map as though I was operating the delta loop back at home. I even manged to get to DP0GVN twice, with a best signal of a very respectable -16dB SNR. It might be considered nothing special, until you consider the absolutely terrible band conditions at present!
Reception reports for 1W, stick antenna on the car, 18:12-18:34UT 2018 Sept 27
After a week of heavy winds and rain, we finally enjoyed quite nice weather for the centenary of the first direct Wales - VK contact over the weekend.
Unfortunately, the bands were terrible! Kp was about 4, with the SFU bottoming-out at a mere 67. Those on SSB were essentially finding nobody to talk to above 40m all weekend long. Luckily, a contact with VK was eventually made. WSPR managed to get the message about our event rather more effectively, spanning the globe on 1W.
Here's my daughter, MW6PYS, who did some digital work, at the Cefn Du Marconi site, near Caernarfon. I was pleased that she asked to go, rather than being pushed into it!
Sunny, but cold, at GB2VK.
After that event, I came home to find 12m was very active on Es yesterday. Everything was working fine with the station. Then I casually went to check things out in the garden, to find two coax outlet points chewed nearly all the way through!
I have always expected that a rat, mouse or some other invader might chew on my coax, but it has never happened in over 7 years of operating here. What could be to blame?
The nibble marks were relatively small, and both cables had been chewed at the point they entered the wall. It didn't look like the work of a rat, not least because a rat would not have been able to chew at that height, and in that way. Rats also sharpen their teeth on harder material than very soft coax.
I thought it could be a rabbit seen in the garden, but I have had rabbits around for years as well.
Nibble, nibble!
It seems that the teeth were very small, so I think it was a mouse or similarly minor rodent. I have been doing some maintenance on the house over the summer, and I think I may have made it more difficult for mice to get in to the roofspace through holes in old timber facing boards. Well, that's the latest theory, anyway!
Luckily, one coax was redundant, and the other, to my 12m Yagi, had plenty of excess length, so it was easily cut and reconnected.
I've now tried to discourage further nibbling by wrapping each coax in split water hosepipe, and then wrapping stainless steel wire mesh around that. Later, I will be buying an air rifle for a more permanent solution!
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. Falling victim to rapid developments in radio, and heavy ice storm damage to cables, the station was dismantled in 1939.
Marconi's voice can be heard at the unveiling of the memorial (pictured below) in 1930 at Wahroonga. Note how remarkably good he was at taking credit!
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...
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.
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:
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 if it's not too close to a car!
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!
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!)
BETTER SOLUTION!
I later tried 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.
The PWM circuit is much better than my own version, because it provides much, much finer control of the motor position, and is as cheap or cheaper than it.
DC motor PWM controller. Great solution for £3, delivered!
I have now tidied this up into a plastic box hand controller. Battery input as banana socket at top, PWM output as BNC to right.
My blogging and operator colleague, Bas, PE4BAS, recently posted a very interesting article on the need for integrated ('press the button and go') digital field transceivers.
Bas' article hits on some very pressing issues within the amateur radio community, although the community itself, for the most part, seems to think those issues don't exist.
Firstly, it is natural enough for most of us to want to operate from the warmth and convenience of our homes. The older you get, the more you want to be in a comfortable place.
But operating from home, even without the often insurmountable local authority consent issues for antennas, is becoming very difficult or impossible for many people. In places like the Netherlands and the UK, which have very high population densities averaging up to 410 people per square kilometre, conflict between hams' needs for quiet RF conditions and others' needs for ever-more electrically-noisy consumer electronics is inevitable - and widespread.
Nice - if you can afford it, and your neighbour doesn't install PV.
Here is a simple situation to illustrate. It very nearly came to happen to me last year, with only the lack of funds next door deciding against proceeding.
You set up a home station. You have read the magazines and decide to make a big investment. Your rig may well cost upwards of £1200. Add in the PSU, ATU, antenna, etc, and you quickly reach a very significant sum of money.
You operate for a few years very successfully, probably having spent more money. Then, one day, a van is parked outside at your neighbour's house. The man starts to install a 4kW solar PV array on the roof. It's entirely lawful, and your neighbours are doing their bit for the environment and their pockets. There are always more people who want a PV system or LED lighting than there are ham operators.
The next day, he switches the system on and, voila! Your whole HF spectrum is full of RFI forever more. If it's not a neighbour, then solar PV 'farms' are now springing up all over the place. There are several very large ones on my island already.
Just one potential source of RFI - now very common everywhere.
Although I do keep raising this as a very big threat to the way hams have traditionally operated, a lot of people don't really take it seriously. Operating from home in much of the western world these days really is putting all your financial (and emotional) eggs into one basket. In the end, most of the RFI-causing installations are lawful and seen as
'more important' than ham radio, and so cannot realistically be
challenged. Regulating authorities have neither the legal basis nor the resources to tackle individuals' RFI issues in most cases.
The only thing between the situation in the video below and you is whether or not your neighbours decide to install PV:
Yet, if we go back to those magazines, they continue to push expensive rigs that, almost exclusively, are only suited to home operation.
Why?
Well, look at the age profile of ham radio operators. It is extremely skewed towards the older, typically retired male. Men like technical 'stuff', and the post-war generation have good pensions with which to buy that stuff. Being older, they don't want to spend time on a cold, windswept beach or stuck in their cars, operating in the field.
It might look laughable, but the DX available at the beach is remarkable. Image: 2E0EDX.
Manufacturers of rigs, therefore, know where the profit is to be made, and have continued to target that older, male generation. Carried through to its logical conclusion, it means that rig makers will, one day in the not too distant future, find themselves trying to sell expensive things to the dead, and having nothing to offer those who remain alive - who just happen also to have a worse (or no) pension.
Over the past few years, love them or loathe them, digital modes have completely transformed ham radio. Gone are the days of fixed thinking about which bands are open at a given point in the solar cycle. Gone is the need for 100W (or, if you are American, much more). Gone is the need for a directional antenna for efficient long-haul DX working. And to any sensible person who has tried it, gone is the need for a powerful laptop and expensive transceiver.
More than enough computing for digimodes. A £32 Raspberry Pi 3B+
Bas' article reminds us that there is an active and increasing population, typically a bit younger, that likes to (or, due to RFI, must) operate digital modes away from the home. For this, we need a small, QRP transceiver, a lightweight, high power density power source, and a computer with reasonable time keeping (and, contrary to so many 'wise' men's words, this does not necessarily mean atomic-level accuracy; +/- a second or two is more than adequate).
These things are not difficult to integrate, yet no manufacturer has really bothered to do it yet. I am not sure why. It seems to be an opportunity that is screaming 'please do this!'
If, like Marconi did, you could gather together all the bits that already exist and put them into a box with an 'on' switch, you could make a very good proft from selling an integrated digimodes transceiver at the price point that people have been led to expect over the years (typically £600 - £1000). Obviously, we should also, perhaps naively for this hobby, expect the price to come down over time.
Marconi: the man who invented putting existing technology into a box - and making a killing!
The way of the future really does not lie in domestic-based operating. There is only RFI to be expected there. The way of the future is in having a compact, self-contained radio system with digital capability that can easily be taken wherever the environment is good.
In the meantime, people like Bas and I create our own works. Although it is not yet tidy and packaged into one unit, I have nevertheless achieved the following in my 'journey':
(1) Kicked out power-hungry, expensive and Windows-based laptops, replacing them with physically much smaller Raspberry Pi computers that use a few Watts of power, and cost a tenth as much.
(2) Carefully approached power management. PV-based battery operating (60-100W panel) on anything other than the darkest winter day (or night!) allows continuous operating at up to about 20W in digimodes with the battery never falling below 12V, and usually remaining well above that. Static mobile operating, especially if supplemented with occasional engine starts or PV for charging, is much the same or, with an engine start at night, better).
(3) Paying attention to the operating environment, and seeking seashore locations. If you have never tried this, the advantage for long-haul DX is spectacular. People on the beach with 5W SSB and an artificially ground-tuned vertical can make daily contacts with VK from the UK, whilst people at home with a Yagi often can't hear VK at all. It sounds silly, but it isn't. The environment is everything.
Not the way to go.
In a very long blogpost, the underlying message is mercifully simple: don't add lead weights to your shoes by over-investing in a home-based station. Always retain the ability to operate away from home!
Yesterday, whilst down the beach with the mobile whip, I noticed that the matching of the antenna was not always reliable. Rather oddly, I found that attaching a short wire to the base of the antenna brought an improvement to about 1.2:1 SWR from an occasional high of over 1.7:1.
I thought this additional wire might adversely affect performance, but I continued to get good signal reports on FT8 from Argentina - even though that direction had no seawater or beach to help me. But it's probably not the best solution, and may give rise to some signal loss.
I came home to read Les Moxon's ever-useful 'HF Antennas for All Locations', which has a good section on losses in mobile antenna systems.
The situation with mobile whips is in no way a simple affair to understand, even though ham outlets tend to suggest it's just a case of sticking a magnetic mount and whip on top of your car and away you go! The difference in capacitance between antenna and car body, and then the capacitance to ground, not to mention earth losses, are complex matters that lend themselves more to empirical, rather than theoretical understanding.
Luckily, I am not actually 'mobile mobile', but static mobile. So this gives a little room for improvements that a moving car couldn't accommodate.
I decided to make a good earth connection between the HF rig and the car's metalwork. I drilled a small hole in the car's boot metalwork, grinding the paint away with a rotary tool. I used a self-tapping screw to give a good physical connection via some copper braid.
Then I made an earth connection for the coax braid side of the antenna system that can be made and unmade using DC crimp connectors used for vehicle applications. I made the connection to the magnetic mount by drilling a hole for a stainless steel bolt in the aluminium bar that connects each magnet.
Testing down at the beach again showed that these two improvements to earth were worth the effort. Now the matching is reliable, and doesn't show strange variations that appeared without them. The SWR is now a consistent 1.2:1, which is very good for a mobile whip.
Of course, if I move the car to another type of ground, which, inevitably in comparison to a beach, will be much poorer, the system will change. In general, the antenna will tend to resonate too high in the band. But because I only really operate at the beach, I don't need to worry about all that.
First call with the new earthing instantly yielded a JA giving me a -11dB report from 15W FT8. Another good result!
Another idea from Les Moxon's imagination is to add short radials above the car roof, to shorten the return current path and so reduce earth resistance losses. I will try that one of these days.
I had a lovely couple of hours down at the seaside again this afternoon, in time for high tide - and lots of Russian, Japanese, and even an Argentinian QSO - all on just 15W and a mobile stick!
I also understood a small problem that was occurring with WSJT-X in FT8 mode. Sometimes, I noticed that, in response to a caller, my reply would be 'de MW1CFN/M -08', which understandably left the caller unsure who I was calling back!
After a few cycles of this, I realised that what was happening was the caller sending a signal report as his first contact, and not his Maidenhead locator. This sends the auto sequencing into this callsign-free reply. This only happens when the callsign has an extension such as /M or /P, presumably because the extra two characters make sticking another callsign into the message exceed the message limit.
Everyone who sends their grid locator first is rewarded with a fault-free sequence of transmissions. The sequence calls CQ with a /M first, then answers with only the normal call, without the /M. It finishes with a 'de MW1CFN/M 73', by which time the other caller is happy enough to accept it, and the logging within WSJT-X correctly records each callsign.
I'm just glad my best two JA contacts did things properly, and were duly confirmed.
Saturday mornings sometimes provide that rare event when the rest of the family have things to do, and I am left with free time to play radio!
So, off I went to the east side of Anglesey, down to Traeth Coch (the 'red beach'), which is well-known for excellent long-haul DX.
75 degrees of wide, open space...
From this location, depending on the tidal state, you either have an extremely large salt marsh environment, or a large extent of seawater immediately in front of you.
The 75 degrees gives this long-DX coverage!
This morning, it happened to be low water on a spring tide. Being very shallow, the sea was nearly 2km away.
I set up the TS480SAT in the boot with my mobile whip for 14MHz. The Raspberry Pi was with me in the front of the car, trying out FT8 at 15W.
Raspberry Pi bringing in signals from the far east.
Certainly, this proved to be a good fishing ground for long DX. I had contacts into the Pacific coastal regions of Russia, and a couple into Japan (although impatient Italians stamped over the JAs, and prevented a confirmation. Grrr!)
Well, I managed a good few calls altogether, and was very happy to get those DX with a very simple, cheap antenna and computer set up.
Horses and radio. Perfect!
Even better was getting to chat with a mother and daughter taking their horses for some exercise. As always, going portable or mobile is a great way to introduce others to radio, and introduce yourself to others' interests!
