This website was created to explain why conditions on our 80m Norfolk Amateur Radio Club Monday night nets on 3.545MHz in the evening at 2030 local time were so variable. Firstly, a 24 hour plot shows the typical diurnal variation of foF2, as seen in the various propagation texts and most amateurs will be aware of the broad sequence of events during the day. What does become interesting is why one day sounds very different to another on the bands and the graphs make this very obvious.

Of course, for a local net you will be using a near vertical incidence skywave (NVIS) refraction from the F2 layer, so the foF2 is a good guide for conditions. This display system has been tested by our club members over a few weeks and several useful operating features have become apparent already.

1. A marked minimum just before dawn, but of course at the height of the F2, this will come much earlier than at the surface, so the curve kicks upwards long before sunrise at ground level.
2. Steep rise to the typical daytime value, but always lots of variation during the daytime period. Band conditions will probably suffer from some D layer absorption too (not shown), which will affect the LF bands such as 160m, 80m 60m and 40m, so all is not as good as the graphs might suggest on the LF bands.
3. Rapid fall off of the foF2 as the solar insolation decays towards sunset. Often a brief window when the D layer absorption has gone and still some ionisation left for foF2 short skip paths within the British Isles late afternoon.
4. There is usually an evening dip, but the times can vary from early to mid evening, followed by a late evening rise in foF2 for the early hours before fading into the pre-dawn minimum.
5. The F2 MUF distance seems to be a very reliable guide. The end of the SSB AFS contest faded quickly leaving just a few stations audible in Norfolk from SW England and Cumbria plus GMs, all confirmed by the 500km F2 MUF being just above 3.5MHz, whereas the foF2 was way below 80m.
6. Once the foF2 has fallen to below your operating frequency, say 3.5MHz, then the bands appear to go ‘long skip’ and this is usually confirmed by the F2 MUF for 3.5MHz only available for distances of 1000km or more with plenty of eastern European stations coming through and not a G to be heard.
7. If you are just interested in the close-in UK conditions for your local nets, then switch off the 3000km F2 MUF to see the foF2 or short skip 100km detail more clearly.
8. foEs has proved very useful in a recent net when the foF2 was around 2.1MHz, yet the 3.5MHz signals were very strong over all local stations, plus out to at least 100km. It turns out that the foEs was 4-5MHz at the time and the most likely propagation was via the E layer.
9. The 3000km F2 MUF can give a heads-up on which of the HF bands may be worth checking, since these will not be adversely affected by D layer absorption.

Several new sections have been added as the site has developed. The Es Blog is used to follow upper air jet stream charts and describe daily Es chances during the main summer season. The EPI section is a new attempt to isolate the main ingredients behind the formation of Es and combine them into a single probability index.

The plots are designed to show the near real-time evolution of the critical frequency ( foF2 ) of the F2 layer and (foEs) for Sporadic-E as measured by the international network of ionosondes. The display system is set up to process data from the USAF ionosonde at RAF Fairford in Gloucestershire on the Cotswolds and from the Rutherford Appleton Laboratory at Chilton in Oxfordshire and Dourbes in Belgium run by the Royal Meteorological Institute of Belgium.

These data are automatically decoded from ionograms and where conditions do not allow a value to be determined automatically, a gap appears in the graph. The displays depend upon the data being uploaded from the measurement station and therefore depends upon many operational factors outside our control. Outages are usually of short duration, so keep checking periodically if data is missing. Data can be accessed from whichever ionosonde (Fairford, Chilton or Dourbes) is available, although the page opens with Chilton as default. The hover-over tool tip will tell you which ionosonde the data point belongs to and the data values.

The purpose of these graphs is to allow radio amateurs to use this professional ionosonde data to improve their understanding of radio propagation conditions heard on the air in relation to actual measured conditions of the ionosphere, as they happen.

TODAY
This graph shows a series of traces, which can be toggled off and on by clicking the label on the key for each line. The graph redraws as elements are changed to give maximum clarity of display. A tool tip showing the value of each data point appears if you hover over any of the lines plotted.

• foF2 : critical frequency of the F2 layer (plotted in red with dots as data points)
• 100km F2 MUF : critical frequency of the F2 layer for a 100km path
• 500km F2 MUF : critical frequency of the F2 layer for a 500km path
• 1000km F2 MUF : critical frequency of the F2 layer for a 1000km path
• 3000km F2 MUF : critical frequency of the F2 layer for a 3000km path
• foEs : critical frequency of Es (plotted purple, where measurements available)
• The operating frequencies of the amateur bands are shown as dotted green lines.
• The times of sunrise/set (at ground level) are shown by the yellow band.

A PDF or PNG can be produced by selecting the three sheets of paper symbol on the top right.

The F2 MUF lines are plotted in increasingly orange shade as the distance increases. If you hover your mouse over a line it becomes bold and shows a tool tip which which gives the actual value of the various elements.

Data is received shortly after the nominal observation time, and the delay can vary from as little as 10minutes to an hour or two, depending upon processing and data transfer within the ionosonde network. The display will plot the latest data when you first log in, you will need to refresh manually to bring in the latest reading subsequently.

ARCHIVE
This page recreates a daily plot of foF2, F2 MUF and foEs for any date going back to December 2016. Obviously, there will be times when data is missing, but most dates are available. The plots are exactly the same as the TODAY display, so refer to the instructions above for details.

NVIS
This is a relatively new section to enable the Spread F Index (fxI) to be plotted and compared with the foF2 and foEs. These three parameters of an ionosonde represent three frequencies that are very important for local nets on the LF bands. Providing at least one of these three frequencies is above the band frequency you are working then you should be able to hear each other. Hitherto, amateurs have tended to regard foF2 as the only indicator of importance, but signals can still be received via spread F, hence the value of plotting the fxI too, which is typically about 700kHz higher than the foF2. When both the foF2 and fxI are below the the band being worked then only long skip paths are available, unless of course you are lucky enough to find Sporadic-E, although this is usually temporary.

COMPARE
This page shows two foF2 traces, the dates of which are individually selectable. The tool tip will show the difference between the two readings. This can be a very useful resource if you want to compare band conditions during recent club nets, or compare the performance of your station or club in the last two RSGB 80mCC contests. The 80mCC are particularly vulnerable early in the year.

AVERAGES
This section shows the monthly averaged hourly foF2 and the maximum foEs by hour. I expect this will show some interesting changes as the solar cycle evolves so take note of the smoothed sunspot number (SSN).

These charts show forecast maps of the height of 300hPa surface (hPa = hecto Pascals, same as mb), which is at an altitude of about 30,000ft. The lines are called the 300hPa contours and, where close together, indicate stronger winds. These can be used to pick out jet streams, which are currents of fast flowing air in the upper atmosphere, which always contain a certain amount of turbulence. Sometimes, at the entrance and exits of the stronger cores (shaded yellow/orange) or where jet streams are disturbed by blowing across mountain ranges, they can generate even more turbulence. This takes the form of atmospheric gravity waves (AGW), a wave motion in the atmosphere which can propagate up to the E region, where the gravity waves interact with the background tidal winds. This can cause the ionisation (thought to comprise of long lasting ions from the ablation (burning up) of meteors, to compress into a thin denser layer which can return high HF or low VHF signals to give Es contacts.

The maps of the height of the 300hPa surface are shown at six-hour intervals during the current day at 0600 UTC, 1200 UTC, 1800 UTC and 0000 UTC and encompass the two main Es operating periods of late morning and early evening. Clicking on the thumbnail image will make it larger and you can step through the sequences using the arrows. The jet stream strength is colour coded starting with green at 60kts through to yellow and then orange. The stronger jet streams produce a better chance of Es.
Zones where the contour pattern is changing most quickly, due to movement or development, are defined by coloured lines; red for decreasing and blue for increasing. These rapid contour changes are particularly good places to generate extra turbulence, since these are regions of rapid changes in the atmosphere.
Other areas on the chart which can contribute to generating AGW are to be found along the axis of an upper ridge. These can often be seen in spells of fine summer weather and may be marked by areas of thin wispy cirrus cloud, looking very turbulent. Severe thunderstorms are another weather feature which is good at producing AGW. These are shown on the map by magenta or orange blobs. These are very much major summer thunderstorms, so are more common over the continent.

There are two radial rings on the map surrounding the UK and they represent the distance range between which Es should typically form to give a single hop path based on a refraction/reflection from the height of the Es patch. The height of Es slowly descends during an opening and the best distances are usually found at the beginning of an event.

A daily Sporadic-E blog is provided during the main season from May to August. This is updated in the morning and can alert the user to significant features on the upper air charts which may drive to prospects for Es during the day.

The map display allows you to select by locator, or clicking on the map, where you want to calculate the probability of Sporadic-E by building a combination EPI, Es Probability Index, based on factors using many of the known parameters which can effect Es. The schematic below shows the main parameters currently being investigated.



The timeline scroll bar at the bottom of the settings panel can be used to see the EPI prediction map over the past 12 hours and as a forecast over the next 12 hours. The default opens with the nearest model time step to the current time. The model weather data behind the map uses the output from the most recent run of the GFS model.

The legend above the time scroll bar shows a relative values of the EPI and after a few examples it would appear that red/purple is where it needs to be for SSB/CW and probably yellow/orange for digital modes.

It includes influences such as time of day, latitude, topography, seasonal effects, meteor input, plus several weather factors for locational prediction driven by weather elements. It does not directly include the Kp index for the quality of the earth’s magnetic field (low values good, high bad) since this changes through the day, but the latest value is shown below the date in the top left hand corner of the map. If the KP is low all is well, but if Kp is 4 or above then conditions will not be as good as the colour coding suggests.

This is a great way to see how a path between stations is related to the ‘hotspots’ of Es probability, as shown by the shading on the map.

Stage 1: Enter the Callsign and locator of the first station or you can simply click on the map for a general location and then enter a generic country name like ENGLAND or anything alphanumeric. The callsign field needs to be filled in with something for the path distance calculation to work.

Stage 2: Enter the details of the distant station as before for the first station. The time will autofill with the time of entry, but you can change this for the time of the QSO, but it needs to be within the span of the data, which is approximately +/- 12 hours of the current time.

Stage 3: Select the band being used by clicking the appropriate radio button.

The display system processes data from two ionosonde stations about 50km apart in southern England, depending upon availability. These are Fairford in Gloucestershire on the Cotswolds, which is part of the USAF Nexion network of monitoring stations, and the other is located at Chilton in Oxfordshire and managed by the Rutherford Appleton Laboratory. A third data source has been added from Dourbes in Belgium which is run by the Royal Meteorological Institute of Belgium to cater for the very rare occasions when both Fairford and Chilton are not available.

The data is accessed via the Global Ionospheric Radio Observatory (GIRO) and is a great resource for HF Ionospheric Sounding Data. The data is stored in the Digital Ionogram Data Base (DIDBase).

Since there is no guarantee that data is available continuously from any station, the graph display will use whichever site is available. In terms of general propagation conditions, these are close enough (<50km) to be interchangeable without losing meaning, and Dourbes is a reserve, which is a bit farther away, although still broadly useful. The amateur radio community is very grateful that such valuable data is available for research into propagation on the amateur radio bands. No commercial use is being made of this data and the work provided here to visualise the data is given freely for educational and research purposes only.

The graphs are hosted by Weatherquest and designed by Jim Bacon G3YLA with helpful feedback from local amateurs and the RSGB PSC. The substantial programming task has been undertaken by my work colleague Dan Holley who took pity on my efforts to produce the graphs manually and should be regarded as an honorary radio amateur after all this!

We welcome all feedback, good or bad - the best way to get in touch with us is to email Jim at g3yla@hotmail.co.uk