I will update the Spring 2023 charts when we get a little closer as they are likely to change as we head towards the maximum of solar cycle 25. 

Anyway, it is nice to see some good predictions of DX on 10 metres and if the past two weeks are anything to go by they are pretty spot on with very loud signals from the USA. 

ARRL's W1AW's CW practice files were romping in the other day on 28.0675MHz Nice to see 10 metres doing what it does best! 

Click here for the charts or use the link on the right-hand side.

As a result of the success of our HF Propagation video on YouTube, which has had 2,000 views in two months, the Propagation Studies Committee has now launched a 20-minute VHF propagation video as well.

The video was originally produced for club presentations, but with Covid-19 and the lockdown, it wasn't getting much use.

So if you have never heard what an auroral contact sounds like, for example, now's your chance!

See https://www.youtube.com/watch?v=5Yo4IFn6AAY&t=8s

Steve G0KYA
Chairman, RSGB Propagation Studies Committee

We highlighted these at the recent Newark Hamfest.

RSGB has now set up quicklinks to each of the tools, which will make it easier in the GB2RS audio bulletin. These are: 

Propquest
Shows real-time critical frequency and MUFs over various path lengths. Excellent tool for HF users.
See www.rsgb.org/propquest

Predtest
Designed by Gwyn G4FKH, calculates the probability of propagation over different paths and for different modes. Includes point-to-point and animated displays.
See www.rsgb.org/predtest

VOACap for RadCom
Shows the probability of propagation to 28 different locations around the world – the same locations used in the RadCom predictions. Can be tweaked for your particular station including mode, gain and power.
See www.rsgb.org/voacap

Proppy for RadCom
Uses the latest ITURHFPPROP tool to calculate the probability of propagation to the same 28 locations used in RadCom.
See www.rsgb.org/proppy

I have just updated my HF short-path propagation prediction charts for the UK (accessed via a link on the right).

I had to update them with the latest smoothed sunspot numbers for the next 12 months.

This is a little depressing as after May 2019 the predicted SSN falls to "one" and stays like that for the rest of the year! Sunspot minimum is currently thought to be later this year, but could spill over into 2020.

These charts are meant as a rough guide. Other tools that are available are:

1. The VOACAP RadCom prediction tool - this replicates the locations found in the monthly RSGB publication, but lets you choose your own mode, power and antennas to give more accuracy.

2. The Predtest.uk tool - this tool, developed by Gwyn Williams G4FKH, uses the latest ITURHFPROP prediction engine to let you produce point-to-point or area propagation predictions, again with full control over the input parameters.

3. Propquest - this is a near real-time tool, developed by Jim G3YLA, that shows the critical frequency and extrapolated maximum usable frequencies available over different path lengths. The critical frequency (the frequency at which a radio wave launched vertically stills gets returned to Earth) is derived from ionosonde data, mainly from Chilton and Fairford.

It should be your first port of call to see what conditions are like. In the summer it also has predictions for Sporadic E, courtesy of Jim.

Steve G0KYA
RSGB PSC Chairman

Space weather prediction is an inexact science. We still don’t fully understand the Sun or how it works.

This means that predicting what HF radio conditions are going to be like over the next seven days can be challenging – especially when you have to produce the forecast a couple of days before it is published.

This week was a perfect example of how to get it wrong!

I prepare the HF part of the RSGB’s GB2RS Propagation Prediction forecast on Thursday afternoon. Jim G3YLA looks at VHF and Sporadic E, before it is sent to John G4BAO who adds some more info on any microwave propagation such as rain scatter and also adds the EME report.

I then edit it, add my HF predictions and send it to RSGB HQ so it can be collated, published and sent to GB2RS readers on Friday.

Sunspots on Thursday 23rd August 2018.

At that point this week the Sun looked fairly innocuous with one tiny sunspot group, a solar flux index of 70 and a sunspot number of 15, representing one sunspot group with five tiny spots.

There were no obvious coronal holes and NOAA predicted the K index would likely be two all week due to a lack of geomagnetic disturbances. The US Air Force agreed.

So far so good!

At 04:45UTC on Monday 20th NOAA had reported:

“Region 2719 (S06, L=133, class/area Bxo/010 on 19 Aug)
developed in the SE quadrant on 19 Aug. No significant flare events
occurred from either region. Other activity included a filament
eruption centered near S11W04 observed lifting off the solar disk at
approximately 19/0538 UTC. An associated coronal mass ejection was
observed off the SW limb in SOHO/LASCO C2 imagery at 19/0812 UTC.
WSA/Enlil modelling of the event suggested the ejecta was primarily
directed westward of the Sun-Earth line and is not expected to cause
any significant effects.”

So the CME wasn’t earth-directed so shouldn’t be a problem – bear with me!

The NOAA report for Monday 20th August said there were no events.
The NOAA report for Tuesday 21st August said there was an RSP (a sweep-frequency radio burst) at 18:46UTC observed at Palahua, Hawaii, USA
The NOAA report for Wednesday 22nd August said there were no events.
The NOAA report for Thursday 23rd August said that at 20:23UTC on Thursday evening the older region 2719 emitted an an “A class” X-ray solar flare. “A class” flares are the weakest and it was after sunset in the UK so didn’t have any major impact for us according to the ionosonde data.

But there were further A class flares on Friday 24th August, which were at 12:47-12:50 UTC, 21:54-21:58 UTC and 21:57-22:01 UTC.

The Chilton and Fairford Ionosondes in the UK show Friday’s flare’s effect at 12:47 as there is a gap in the data.

You can see this at Jim G3YLA’s Propquest site at: http://www.propquest.co.uk/graphs.php?type=archive

But by Saturday 25th August a new large sunspot group had appeared.

By Friday another new sunspot group (2720) had emerged, which grew rapidly and by Saturday it was quite large. Sunspot AR2720 is not only large, but also strange. Its magnetic polarity is reversed. The North and South ends of its magnetic field are backwards compared to the norm for sunspots in decaying Solar Cycle 24.

So could AR2720 be from the next solar cycle, Solar Cycle 25? We’ve already had one reverse polarity sunspot which has been attributed to Cycle 25, but that was last year. This is going to be discussed over the coming weeks.

Action on Friday 24th August continued.

From 02:00UTC a series of solar flares were recorded, mainly from the new region 2720. These were B-class solar flares.

By the early hours of Sunday morning, 26th August the K index had started to climb, peaking at Kp7 at 03:00 and 06:0UTC. The bands on Sunday were lousy with a lack of signals across the board in the UK as the ionosphere collapsed. The 14.100MHz IARU beacons were all inaudible.

The Kp index hit 7 in the early hours of Sunday 26th August 2018.

A sweep with my SDRPlay receiver and SDRUno software saw very few signals on 20m at all and virtually nothing higher in frequency. There were a few weak and watery CW signals from Germany on 40m.

So what was the cause?

NOAA now says there had been an earth-directed coronal mass ejection on Monday 20th August that no-one seemed to comment on at the time. NOAA’s own records don’t show any solar flares on Monday August 20th – see (ftp://ftp.swpc.noaa.gov/pub/indices/events/20180820events.txt)

So was it this CME or the one on the 19th that is now reported as causing the high-speed solar wind stream that brought about the Kp7 event and auroral conditions? The experts seem to think so – now!

Or was it a CME as a result of the solar flares on Friday 24th August? That to me would seem more likely and fit in with the roughly two-day solar wind transit time to Earth.

SpaceWeather.com described it as a “surprise geomagnetic storm” and I think that’s a pretty apt description as no-one predicted it.

If that is the case there is no way I could have known about it when I filed the copy to RSGB on Friday morning. This report predicted quiet geomagnetic conditions for the week commending Sunday 26th August – I don’t think so somehow!

Oh, the joys of space weather and HF radio propagation forecasting!

Propagation predictions for the International Beacon Chain for the UK, May 2018.

In an effort to try to make HF propagation predictions more accurate I have been playing with a different method of producing them using the ITURHFPROP software.

Previously I had been calculating the field strength of each beacon and then converting that to an S point level. It was pointed out that this isn't the best way and that calculating the signal strength in dBm and then converting it would be better.

They are based on 100W to a dipole at 10m - we know that the IBP chain use a Cushcraft R5 antenna.

I then hit the problem as to what antenna gain do you use. This may sound simplistic, but in fact it isn't as the actual gain off a dipole will depend upon its height, its orientation and the required take-off angle.

Now, the take-off angle will depend upon what ionospheric mode is dominant at that point in time. That is, is it one F-layer hop, two F-layer hops or a combination of E and F-layer hops.

After a lot of thought and discussion I settled on setting the gain at both ends at 0dBi, which appears to give reasonable results - setting it at 2.15dBi gave over-optimistic results

Anyway, attached is the plot of predictions for the beacon chain for May 2018. I'll check to see how accurate it is and adjust the input files accordingly. The ultimate goal is to the transfer these settings to other HF predictions.

If anyone wants to report on whether they find these accurate or not please let me know. They are median predictions, which means some days may be better, some days worse.

Just click on the chart to enlarge it.

Over Christmas and the New Year I got better acquainted with the ITURHFPROP propagation prediction software.

This is the software that Gwyn G4FKH uses to produce the monthly HF predictions for RSGB’s RadCom magazine and which was produced by the ITU.

Gwyn adapted it to produce a graphical output, which can be found at www.predtest.uk

But I was intrigued to see if I could use it to produce some predictions for the worldwide International Beacon Project (IBP) chain that runs on 14, 18, 21, 24 and 28MHz. I won’t go into too many details here about the IBP network as you can find all you would want to know at http://www.ncdxf.org/beacon/

The good news is that as they all use the same power output (100W max.) and the same antenna (pretty much a unity gain or +2.15dBi antenna) it should be fairly easy to model what the expected signal strength should be here in the UK.

ITURHFPROP runs in Windows and uses an input file with all the parameters needed, such as your QTH lat. and long., the transmitter’s lat. and long., required SNR, bandwidth, smoothed sunspot number, power etc etc.

You then run it from the command line and it creates an output file.

I ended up creating input files for each of the beacons, and a spreadsheet that can take each of the output Field Strength (dB(1uV/m)) figures and convert them into S units.

I then created a batch file that runs all of the predictions for each of the beacons in one go. With an I5 processor this takes less than about 15 seconds.

The spreadsheet then formats these so that I can produce the chart you see on the page. This may sound long-winded, but it really doesn’t take long. I’m sure someone with Python programming skills could automate the whole thing, but I wanted to make sure it worked first before going any further.

The end result has proved to be quite accurate and shows that at this point in the sunspot cycle we can’t expect miracles in terms of hearing the distant beacons. While some are audible on 14 and 18MHz, generally we are not hearing much above that.

In the UK, what have been audible quite regularly this month on 14.100MHz are RR90 (Novosibirsk, Siberia), CS3B (Madeira), 4U1UN (New York) and occasionally 4X6TU (Tel Aviv).

It also shows what the effect of an elevated K index can be as this generally means the beacons are less audible (if there at all) as the MUF declines. We have been suffering from the adverse effects of coronal holes recently and that isn't going to end any time soon.

You can see the predicted MUF over different path lengths in near real-time using the graphed ionosonde data for the UK at http://www.convectiveweather.co.uk/ionosphere/graphs.php?type=live

This was produced by fellow RSGB Propagation Studies Committee member Jim G3YLA and his colleagues at Weatherquest in Norwich.

I’ve posted the predictions here to see if they are of interest to anyone. If they are I’ll update them monthly.

To view the January IBP prediction chart full size just click here.

I have now updated my propagation maps with the latest predicted smoothed sunspot numbers for the period up until the end of June 2018.

You can access them using this link.

The sunspot numbers continue to fall as we head towards sunspot minimum sometime around 2019.

If you use the charts look for about 60-70% reliability for SSB (yellow or hotter) and perhaps 40-50% for CW or PSK (green). For FT8 you may be able to work stations where the reliability is down to 20-30% (blue).

Of course, these are a guide and if you want to try making charts for your own station I recommend the online software at either voacap.com or www.predtest.uk/

The effects of coronal holes are likely to continue for a couple of years.

This weekend I’ll be giving a talk at the RSGB conference on “HF Propagation at Sunspot Minimum.”

This will show that we can expect the minimum to be around late 2019 or 2020. It is hard to be precise, as the minimum is something you can define after the event, not before or during!

What I will say is that we can probably expect the effects of solar coronal holes to continue, at least until we are well into the minimum.

Geomagnetic storms can cause problems on HF, although they can also bring short-lived ionospheric enhancements so they are a double-edged sword.

For example, on Tuesday 10th October the bands were open to DX all the way up to 12 metres. But as the solar wind from the coronal hole hit on Wednesday, apart from a short-lived ionospheric enhancement the MUFs took a dive.

By Thursday (12th) lunchtime, 20m was struggling to fully open and 17m was showing very little activity indeed. But by Thursday afternoon, and with a K of 5,  I had worked Saudi Arabia on 10m SSB.

This shows that at sunspot minimum with a solar flux index of just 66, quiet geomagnetic conditions may be better than stormy ones. So look for a K index in three 0-2 range, not 5-7! But then again, when solar plasma first hits the earth we may get some short-lived enhancements right up to 10m, so a high initial K index can work for us.

For those who weren't at the lecture, I showed that monthly average maximum useable frequencies will decline with the sunspot number. This doesn't mean there won't be F2-layer openings on 21MHz and higher, just that they won't be as reliable or as long lasting.

Other than that I encourage people to play with a propagation program to get an idea of what might be possible.

My suggestions are:

Windows based

VOAProp

HAMcap

W6ELProp (when installing, right click and run as administrator on Windows 10)

VOACAP


Online

VOACAP.com

Predtest.uk


Other sources of info I mention are:

Solarham.com

NOAA – Space Weather Prediction Centre

Real-time F2 critical frequency display (this will soon move to Propquest.co.uk)

Smoothed Sunspot Numbers

Latest extreme UV image of the sun from the Solar Dynamics Observatory spacecraft (shows coronal holes)

Lastly, I talk about the difficulties of predicting openings with FT8. One suggestion is to use VOACAP and set the required SNR to a figure of -20dB or so. It is usually set to about 24-31dB for CW and 45 for SSB. This is still experimental (as some SNR figures are quoted as dB per Hz, while others are quoted in a 2500Hz bandwidth), so you might have to play with it. VOACAP’s settings are critical and it is worth reading the notes on the VOACAP website and also the “Top 10 mistakes in using VOACAP”.