Three Days of 40m WSPR - Short Vertical.

Some extended results from the short vertical that I've been running at the marsh site are now available.

The results are extremely good, and way beyond what I expected.

The best comparison station in the UK I could find was G7MRV, who was by far the closest of any others to the performance of my antenna.  Irritatingly, there are no details about the antenna in use at G7MRV, and no reply has yet come back to an e-mail approach:

Across all distances, my antenna was 0.4dB weaker than G7MRV:

But when considering long-haul DX (beyond 4400km), things change considerably, now favouring my antenna by 3dB - twice the signal strength.

Better than that was the fact that I reached several DX stations that the G7 couldn't reach at all.  I've selected the latest spot from VK7JJ, but the reliable result comes from the plot above, which takes account of very many more spots at each station:

That's certainly enough testing to demonstrate the antenna - just 5m long on a 7m pole and two elevated radials - is very effective.

DP0GVN Hearing MW1CFN - 7MHz

Last night saw a significant transient geomagnetic disturbance commence around 21:40UT, as the Kiruna magnetogram shows:

IRF - Kiruna.

Interestingly, the S/N to DP0GVN fluctuated transiently at much the same time:

DP0GVN WSPR Spots

Here's how my 200mW, 7MHz signal from a shortened, 5m vertical to DP0GVN varied with time last night and this morning:

Geomagnetic conditions were pretty stable:

Image: IRF, Kiruna.

WSPRs and Wet Strings.

Amateur radio is a hobby that attracts the curious and, in general, well-educated.

It's also a hobby that attracts stubborn men, who prefer Donald Trump-esque fixed ideas, rather than open their minds to the complexity of life.

A good antenna?  Hardly.  Image: Wikicommons/Nevit Dilmen.

I often hear operators - and I'm afraid they are usually American - claim that, because WSPR signals can be heard by "any old wet string", the propagation and antenna tests we run are of no real-world significance, because we "would never get a QSO in other modes".

As soon as I hear this kind of thing, I know it's time to stop trying to contribute to anything like an informed debate.

Yesterday, the weakest spot I received was -33dB on WSPR, using 200mW.  That's about as low as WSPR can get. Of course, the question why that spot was -33dB can have many different answers.

It could be an operator with a very noisy environment.  He could have a rubbish receive antenna.  My signal could be very weak.  It could be a transient propagation enhancement.  It could be a high angle signal when the antenna favours low angle.  Lots of things it could be.

WSPR: it's not 'fake news', folks.  Image: Wikicommons/By Gage Skidmore from Peoria, AZ, USA.

Reasons aside, the claim remains that someone hearing a WSPR signal will not hear other modes.

This is all very odd, because JT65 is meant to reach down to about -24dB before reaching a 50% error rate, and JT9 down to about -26dB.  The fact that there is a certain error rate creeping in does not, of course, mean that we won't decode a weaker signal and, indeed, we all do receive weaker ones regularly.

The software in use also makes a difference.  JTDX, from practical experience, clearly decodes weak signals much more effectively than the original WSJT-X software.  One hardly ever sees multiple, overlaid decodes, often differing by 20dB or more, using WSJT-X, whereas they are rather common with JTDX.  Accordingly, JTDX can probably reach reliable decodes at a significantly weaker S/N than expected under the native software.

There are three things the stubborn old men fail to understand:

(1) Many modern weak signal QSO modes are entirely capable of hearing and decoding at the same approximate level, and therefore out to much the same DX distances, that the WSPR mode attains.  There is no drastic difference in each mode's capability by now.

(2) Many WSPR operators, pushed by the likes of WSPRlite transmitters, are now settling on QRPp outputs of 200mW or less.  This output level is usually much lower than the power operators will use for 'real QSO' modes like JT65 and JT9, where 5-10W is the norm.  As a result, if someone is hearing you with 200mW WSPR, there is little question they will hear you with 10W JT65A, even if we allow for the somewhat lesser sensitivity of the latter mode.  Even OLIVIA, which has a nominal sensitivity limit, probably exceeded in practice, of -14dB S/N.  This sometimes has the unnerving effect of having a near copy-perfect QSO when no signal is visible on-screen!

(3) One should spend a lot of time carefully experimenting, rather than adopting an opinion that has no basis in evidence.

So, if you hear that old 'wet string' thing again, just turn the other way.  No amount of evidence will sway the Trump-esque amongst us!

Short 40m Vertical - WSPR tests.

Last summer, I wrote about an experimental, centre-loaded vertical for 40m that, surprise, surprise, worked rather well.

The only problem then was that my QTH is rather full of antennas, and I wanted to set up the short vert in a clear site, where it could all be carefully tweaked for peak performance.

With a new marsh site to play in, I now had the chance to do exactly this!

Here are the afternoon-evening WSPR results of the short vertical compared to a half-sloper, which is cut for 40m, hung and fed against my lattice tower:

Comparison of S/N, all distances.

The advantage over all distances is significantly in favour of the short vertical, at 2dB better than the half sloper.

This was the range outcome:

MW1CFN (blue) = short vertical; MW6PYS (red) = half sloper.

Overall, a slight advantage in range terms to the half sloper.  Here's the map of spots, showing DP0GVN hearing both stations (this is only one set of spots of many):

Next, a quick look at how the S/N compares out beyond 2400km, which I choose as the boundary between DX and non-DX:

A slight advantage of 0.75dB to the short vertical.

Comparison with G0ORD at long-haul DX, running what I think is an inverted-L at much higher output  (5W), looks like this:

Looking carefully at all other stations in the UK, the WSPR database shows that only G0MRV approaches the effectiveness of this antenna, although on sheer DX reach, he does not overtake the short vert.  The vertical performs at the same or slightly better level as a half sloper hung off a metal tower in a similar environment.  So, just like last summer, the objective, human-free WSPR tests confirm the short vertical is in no way a compromise antenna, and is indeed a very effective one, doing very well against full wire antennas running higher output.

The real advantage for the short vertical is that it fits easily on a cheap 7m-tall fishing pole, resists very strong winds (tested to 50mph so far), and is generally much easier to accommodate than a half sloper (needing a fixed metal pole of significant height) or dipole (needing two or three such supports).  It's also very portable, and very easily deployed wherever the fancy takes you!

14MHz ground wave at night.

An interesting phenomenon recently has been the near-continuous reception of my daughter's WSPR beacon by G0LUJ throughout the night time, when propagation via the ionosphere has died completely.

Although my daughter's elevated vertical and my own are identical in every way, G0LUJ does not generally hear my beacon.  This is probably due to slightly higher ground to my NE, whereas the alternative, marsh site is flat all the way around.

I thought it may be interesting to plot the strength of the WSPR signal heard by G0LUJ, to see if it conformed to any discernible pattern.

SNR of MW6PYS as heard at G0LUJ (RX antenna/site details not published)

The fairly sharp peak around 22:15UT coincides nicely with a significant, brief disturbance in the geomagnetic field to Kp=5.  The second, broader peak towards dawn looks like the the early dawn effect.

This is quite interesting, because the first peak probably reveals the extent of a weak but definite propagation enhancement. 

It seems the ground wave, steadily received at around -27dB is 'overtaken' by modest and transient ionospheric propagation due to the geomagnetic disturbance, increasing the received signal strength by 8dB (or 6 times the ground wave signal strength) at peak.

Great new semi-/P operating location.

Many years ago, as a teenager interested in astronomy, I was given kind permission to use an old water pump building in the middle of a big field to store and act as a base for my telescope(s).  Until then, I had to carry the whole instument in pieces in my little Ford Fiesta, often attracting a stop from police at 1am!

After some years, I had an observatory at home, and stopped using the field.

My 280mm and 158mm Newtonians in the field, about 1990.

Recently, with a mind to freeing myself from the home QTH, I thought it would be very useful to have access to that field and its pump house again for more scientific fun.  The person from whom I gained permission, which was granted so long as I needed it, died many years ago.  So the new owner or renter may be surprised and not like me turning up again, all of a sudden.

Anyhow, I visited the pumphouse this afternoon, and found that I had left the door padlocked, although I was sure I had left it unlocked when I stopped using it in the early 2000s.  Taking a photo through a very small opening with my phone's camera and flash, I could see parts of the old telescope cover and a small desk were still inside, just like I left them nearly 20 years ago!

Time capsule - very odd to see this still there (including the car battery and an old jamjar magnetometer (magnet and mirror on a thread in a coffee jar!)

The field is very wet, being essentially a marsh where water levels rise to a temporary lake in winter.  It's ideal for radio, because it is very open, with an almost flat horizon all around.  It is also far away from any RFI, being one of the most isolated spots on the island.

Terrain profile from the marsh to USA (280 degrees)

Terrain profile from copper mine site to USA (280 degrees)

My dad, now 85 years old and who helped me build a base and cover for my telescope mount all those years ago, knows just about every landowner on Anglesey.  So I called in for a cup of tea and asked who owned the field.

Turns out the person who gave me permission was only renting the field, so couldn't really, at least in the strict legal sense, have given valid permission for someone else to access it.  Still, I never caused any problems, and so it was no issue.  My dad knew who the landowner was, a man from a semi-aristocratic family who came to Anglesey without any Welsh language at the age of 10, but who now sounds just like a native, albeit with a hint of aristocratic English underneath it all!

Within seconds of explaining why I had turned up on the farm on a bitterly cold day, and who's son I was, I had hand-waving 'of course you can' permission to enter the land and use the pumphouse again.  That's the very best hospitality of Wales, though increasingly a rare thing in today's litigious society.

The new grid is IO73th, grid square SH47. 

The possibilities are now very good, and there are even a few mature trees from which to hang larger verticals or v-beams. With a basic but perfectly weather-proof building to shelter in, it will be easy to run laptops and such like with little difficulty.  Maybe I'll ask if I can put a solar panel or two up in a little while, or perhaps even grab an old Honda generator!

MW6PYS now transmitting from the new site on WSPR (14MHz).

UPDATE:

WSPR site comparison tests at 14MHz from mid-afternoon onwards after installation at the marsh show essentially neck-and-neck performance between two identical verticals, one at the copper mine, the other at the marsh (pictured above).  This, despite the sea not being visible and the site in a slight depression at the marsh.

Open marsh (MW6PYS, red) vs. Copper mine (MW1CFN, blue)

Signal/noise at the receiver when all distances are taken into account, comes out at the marsh site being very slightly (0.5dB) better than the copper mine site.  I have an issue with DXPlorer's use of arithmetic mean, though, because the median is better for the type of outliers one sees with signal propagation.  Using the median of 60 spots, the outcome is 0dB - no difference at all between the two.  I expected the copper mine to have done better as the signal angles reduced, but this doesn't happen in practice, perhaps hinting at a practical limit to 'takeoff' angles, even when the ground is elevated and sloping towards the visible sea, as it does at the copper mine.

For this discussion, though, I am not really interested in spots from Europe, so I am focusing on the DX performance.

All distances, with arithmetic mean computation.

When limiting the spots to those beyond 4600km, the situation changes markedly, with the marsh site 1.95dB better using the mean, 2dB better on median.  Again, I'm amazed.

Spots beyond 4600km.

All spots on the first afternoon to evening run:

Second day's (longer) WSPR run.

In the period of mid-morning to late afternoon (21/01/18), at DX distances beyond 4000km, the marsh site was up to 3.5dB (on arithmetic mean) better than the copper mine site.  This reflects the data from day 1, and we can settle on a consistent difference of at least 2dB for DX spots in favour of the marsh site for much of the day.

In terms of relative power, a 3.5 dB increase over 200mW amounts to the signal 448mW would give - a factor of over two times.

7.5hours of range data.  Marsh site (red), copper mine (blue).

The range graph shows a small but significant increase in DX range for the marsh site, and also a greater maximum range.

Considering (below) all 208 simultaneous spots, over all distances over the 7.5 hours of the test, the marsh site is 2.7dB better than the copper mine site. 

Beyond 4000km, the situation (below) is even better: a difference of 3.5dB.

Overall, then, and although there is a small change with time of day in the degree of advantage for the marsh site, it is always better, falling typically between 0.5 and 3.5dB.  I think I can be very happy with the new site!

Day 3 - morning run.

Last evening saw an extremely sharp cut-off in spots from much of anywhere.  At about 19UT, I looked at WSPRnet and was only being heard by two Italian stations.  With a change in the wind direction and strength, and having stays that only supported the antenna from the opposite direction, I was worried the system had fallen over!

Having trudged in the dark through an extraordinarily wet field and sinking to my shins at one point, I reached the antenna to find it was perfectly fine.  Having checked all the connections and reset the WSPRlite, all looked fine.  When I got home and looked at the magnetogram in Sweden, it was clear that a significant disturbance in the geomagnetic field had occurred, wiping 20m propagation clean away.

This morning, then, with very sbudued propagation on the recovery from last evening's disturbance, I gathered morning comparison data from about 07 until 12UT.

The range persists as significantly better for the marsh site (red):

The reported SNR advantage across all distances for the marsh site is the highest yet seen, at 4dB (2.5 times) better than the copper mine site:

Beyond 2400km, the SNR advantage is 2.4dB better for the marsh site:

Before I finish, I have to compare the marsh site with other WSPR stations.  I stress that the stations chosen are merely those with a decent number of spots, and which have been checked against many other stations to ensure they provide a typical comparison.  No stations came close to the performance of the marsh site.

First, here's someone running 5W.  The marsh matches the range using over 12dB less signal - just 0.2W.

Next, here's a station also running 200mW, with spots limited to good DX (more than 4000km) - a benefit for the marsh of over 4dB.  All data, by the way, is over just under 3 days in total:

The mean and peak range were considerably better for the marsh site at all times of day: