Since AA7FV told me he was receiving the strongest spots he'd ever seen on WSPR at 14MHz, I've been taking more of an interest in what's going on.
Last night, the signal reached a new record, with two spots at -2dB SNR from 2W into a large rhombic antenna at AA7FV. My antenna is a vertical delta loop in quiet conditions.
The pattern of the spots, when plotted out, looks like this. Y scale is SNR in dB:
The pattern, which comes to an abrupt halt after the 00UT spot, clearly trends upwards from a fairly low SNR in my local early evening, peaking strongly in the period 22-00UT.
I've noticed this kind of thing many times before, and the timing appears to be related to the passing of magnetic midnight at roughly mid-Atlantic longitudes:
Situation at peak spot strength. Image NOAA.
The great circle path between AA7FV and myself is thus:
Great circle path. Image: Google.
The path, if it is the same as the great circle path (which may not be the case) from AA7FV goes straight into the magnetic midnight sector where it finds a quiet conditions aurora between Greenland and Iceland, although the signal enters the overall auroral oval much earlier, over the northern extremities of Quebec.
It is possible, perhaps even likely, that the AA7FV signal takes more of a tangential path to the aurora that may then skew its path towards the UK. This is very difficult to demonstrate, but has certainly ben noted in abundance in the scientific literature, where up to 100 degree deviations from the great circle path have been determined.
Superficially, this seems to suggest that some form of enhanced ionisation exists in this auroral zone that considerably boosts the signal strength over what it would be without it. This occurs repeatedly from night to night, so the link with the auroral oval seems strong, especially as the signal vanishes soon after my local midnight.
As always, any informed insights welcome under comments!
Propagation has been a bit rubbish over the past few days, and efforts with my special call GB0BYS have been tough going, despite managing contacts on all bands from 80-10m with one day left to go.
I had an interesting email yesterday from AA7FV, based about 15 miles north of Tucson, Arizona. The title was 'What antenna?'
Darrel, an UK ex-pat, told me of his surprise to receive a -3dB S/N report from my WSPR reception on 14MHz, using the GB0BYL call.
Darrel commented, speculating that I "must have an extraordinary antenna there to be able to
give me a -3 dB s/n report"
"I have rarely - in fact I think never - had such a good report
from Europe or the UK. Other WSPR reports I was receiving from
Europe or the UK at the time were typically 20 dB weaker than
that."
Darrel knows what he's talking about. He's a semi-retired professional astronomer with a Physics Ph.D. from Cambridge University. Even better than his academic qualifications is his rhombic antenna pointing at Europe. A rhombic like this has a typical gain in excess of 15dBi on its main, very narrow front and rear lobes.
Even with my standard vertical delta loop as the antenna for 14MHz, I've managed contacts - either TX or RX - when others are unable to, over a long period of time and I've blogged about them regularly. Others tend to think this is machoistic bravado, but I see it only as reporting what happens from a clear, elevated, highly mineralised site overlooking the sea. Magic and bravado aren't necessary. The environment and consequent antenna pattern (i.e. extremely low, even sub-horizontal radiation) is what makes it all happen.
To reinforce the great potential of my QTH, I happened to pick up the tiny 10mW from ZL1RS' BB05 balloon, and making its way eastwards across the Pacific, lying close to Easter Island at the time.
Now tell me the QTH isn't a good radio site!
The critical thing is that, at the time of consulting the WSPR database (evening of 27/04/2018), I was one of only two stations across Europe, Africa and Asia (one station from JA) that had heard from the balloon since its launch, 3 days earlier. Curiously, ZL1RS says that the transmitter is 50mW, whereas the WSPR reception reports issued by all stations claimed 10mW. Either way, it's a long way for a tiny signal, even from 30,000 feet and a full vertical dipole dangling underneath the balloon!
So, I think I am now content, faced with all this entirely non-biased, human-free WSPR assessment, that this QTH is very special for radio, and that it yields world-beating performance from simple (but always well-made and matched) wire antennas.
I hate to think how much time I've spent building antennas over the years. But one thing I don't have to worry about is having spent too much money on them.
A long time ago, I wrote about a simple multiband end-loaded vertical that has, by a very wide margin, become the most read article of any in this blog. I'm also glad to say that a number of people have contacted me to tell me how they built their own and found it very effective.
A 20-6m vertical for £50 or less!
Spending more time at my 'weekend' shack these days, I decided to finally deploy my all-aluminium version of the I-AM antenna in the field. This has been lying around under various stages of development for around two years, so it was nice to get it away from the garden and into practical use!
The main advantage to me at this site is the ability to reliably and quickly disassemble the antenna into smaller parts that can be stored when not in use, and the rapid deployment due to there being no radials or much by way of a support mast, etc.
The antenna in this version is also very physically strong, and can withstand the kinds of accidents and occasional encounter with cows and sheep that operating in the field inevitably brings!
To recap the basics:
The antenna is a vertical dipole, except it is made physically much shorter by cutting each 'leg' in half, and joining the other half on top of the first in a 'T' arrangement.
Aluminium (and many other materials) are often sold in 2.5m lengths, which makes them readily car-transportable. This is very useful, because the electrical length of each leg of a 20m dipole is almost exactly 5m.
Using simple 'wing' nuts that can be operated easily without tools, the horizontal end loads can be attached and detached from the vertical sections for easy transport/storage.
Insulation between the dipole legs can be achieved by several methods. The original version I built was simply timber end load supports with wires running along them, then some vertical wire strapped onto a fibreglass (insulating) fishing pole. For the current version, I used Delrin plastic inserts both for inter-leg insulation and as the physical support at ground level, which also needs to be insulated.
Feed point contacts in my case are metal straps secured to the poles with stainless steel hose ('Jubilee') clamps. A better arrangement that I will use shortly is a bolt through the pole, and a ring connector from there to the feedline.
The commercial version of the end-loaded vertical is the I-Pro Home, currently sold by Nevada at £259. There has recently been talk of Pro Antennas returning to sales in their own right, but their website is currently (21/4/18) reporting a '404'.
Easily split into two halves for storage/transport.
The cost of building your own I-AM antenna will only be roughly £50 in all-new materials, made up mostly of the aluminium tubes and Delrin rod. Other bits you will have lying around. Ebay is a good place to find all the materials if you choose your sellers carefully.
The I-Pro Home commercial antenna uses a 4:1 transformer at the feedpoint of the vertical. Whilst this works just fine, it is not the best arrangement. Firstly, it adds substantial weight to an already rather top-heavy antenna.
Secondly, for an antenna that must be matched with an ATU on most or all bands, it makes much more sense to use a direct feed with 300 Ohm twin wire running either to a balanced line ATU, or directly to your rig or unbalanced line ATU via a 4:1 balun on the floor or a wall near the transceiver, and a very short length of coax to finish the connection.
Full HF sweep of my I-AM antenna in an open field setting. From 20m up (which is the design intention), the SWR remains within easily matched limits.
The reason for this is that the antenna works at relatively high SWR, where losses are very much higher with coax - up to 20 times higher - than if twin wire is used. The higher SWR itself is not a problem and should not be viewed as such, because it is, of itself, a lossless phenomenon. Those reflected waves do ultimately get radiated.
End load attachment method. Wing nuts permit easy mounting/dismounting.
Last night I confirmed again that this antenna matches up on 20-6m, although the internal ATU was getting towards its limits at 6m. With an external ATU, you will probably manage a match on 30 and possibly 40m, but it probably won't be very good on the latter band.
One solution for feedline attachment. A bolt with a ring connector is a better one!
My first call last night was to A41NN in a pile-up on 14.200MHz. I was rather pleased with that! I look forward to using the I-AM as my main operating antenna from this /P site from now on. UPDATE:
I had a very quick chance to run WSPR on 20m using a very old and simple manual ATU to my WSPRlite recently. Free time for a longer run will come at some point.
I compare my antenna with a GI station running 1W as opposed to my 200mW, who is known to be a very good performer and a consistent reference station for me.
As you can see, whilst the data is very limited, and mindful of the more than 6dB greater output from the GI station, the WSPR results do clearly show this vertical end loaded dipole is performing very well indeed.
A brief period of WSPR propagation testing at 10MHz the other evening revealed an interesting spot of my signal that I don't think I've ever seen before.
Because I've worked on smaller research vessels, I was very interested to see my signal was heard by GM0HCQ/MM, a WSPR station on board the RV James Clark Ross.
WSPRing its homecoming.
A look on the AIS site confirmed my expecation that the ship was returning home to the UK after a summer in Antarctic. The latest port of departure was Port Stanley in the Falkland Islands.
Although the recent survey on amateur radio is necessarily non-scientific and heavily US-centric, it is certainly worth a read and very thought-provoking.
It seems the clash of the generations is playing out in the hobby quite strongly, with old operators blaming youngsters, and youn operators blaming old timers. I guess it was always thus, but it is disappointing and sad to see a 'blame game' play out.
In late April 1986, I was listening to MW commercial radio from
Germany at home. It was advising people in Germany to close their
windows and remain indoors for a couple of days. There had been some
kind of accident in Ukraine.
A day or so later, I was out fishing for trout at my local lake on a fairly warm but very wet day.
Later that day, I learned about the true scale of what had happened. It was, of course, the Chernobyl catastrophe.
Whilst
it's over 1000 miles away from Wales, the winds on that week conspired
to flow eastward. Together with very heavy rain, this weather pattern
caused a considerable amount of radioactive fallout from Chernobyl to be
deposited on North Wales, especially the high ground of Snowdonia.
This
was more than a technological catastrophe. Countless people died and
many more suffered terrible health effects - and continue to do so.
Controls on the movement and sale of sheep in the more seriously affected areas of North Wales were not removed until 2012 - 26 years after the disaster.
So
this was a big event of the time. I always remember it and the grey,
rainy day where I was being soaked with radioactive rain as I fished by
the lake.
This
year, I applied for GB0BYL as a SES call to commemorate the 32nd
anniversary of the catastrophe. As I wrote the QRZ.com page, I thought
it would be a good idea to link the callsign on QRZ.com to a charity
that helps the children of Chernobyl, who continue to suffer terrible
diseases linked to the radiation loading from the accident.
I
also came to think that amateur radio is always repeating its claim to
be very useful in disaster relief. It's very much an US-centric thing
that doesn't really find much application elsewhere. Many of think it's
an exaggeration, others a falsehood, that ham radio has any significant
role to play in such work.
But I also came to realise that supporting worthwhile causes through raising the profile of charities via amateur radio is something we can meaningfully do, even if the increase in support and donations might only be modest.
