User Guide
INTRODUCTION
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.
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 will be used from whichever ionosonde (Fairford or Chilton) is available in the case of a missing report. The hover-over tool tip will tell you which ionosonde the data point belongs to.
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 on the ionosphere, as they happen.
OPENING PAGE AND DISPLAY OPTIONS
The opening page gives the display options available as a set of buttons.
Live Data : Near real time foF2, foEs and F2 MUFs for different skip distances
Archive : Select dates in past to recreate the Live Data display
Compare : Compare foF2 today with another selectable date (i.e. what was last week’s net like)
Averages : Building up list of historical averages for previous complete months
Data Credits : Acknowledgements and data sources
User Guide : Notes for Radio Amateurs
LIVE DATA
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.
Today foF2 : critical frequency of the F2 layer (plotted in red with dots as data points)
Today 100km F2 MUF : critical frequency of the F2 layer for a 100km path
Today 500km F2 MUF : critical frequency of the F2 layer for a 500km path
Today 1000km F2 MUF : critical frequency of the F2 layer for a 1000km path
Today 3000km F2 MUF : critical frequency of the F2 layer for a 3000km path
Monday 23rd Jan 2017 foF2 : critical frequency of the F2 layer yesterday (plotted in blue with dots as data points).
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 LIVE DATA display, so refer to the instructions above for details.
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 average of 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).
JET STREAMS
This section shows the current day’s forecast 300mb jet stream charts at 06z, 12z, 18z and 00z so that users can see regions where jet streams are present. Weather features have been known to generate turbulence, which in turn produces gravity waves that can propagate upwards to reach the E region, where in turn, they interact with the atmospheric tidal winds and may result in Sporadic E. Other weather features which may cause weather turbulence are thunderstorms (shown as magenta regions) and rapidly changing upper air patterns delineated by red (falling) or blue (rising) contours in the 300mb pressure pattern.
A Sporadic E commentary will be added during the Es season May-August.
USING THE CRITICAL FREQUENCY AND F2 MUF
This display was produced 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.
DISPLAY OPTIONS
The opening page gives the display options available as a set of buttons.
Live Data : Near real time foF2, foEs and F2 MUFs for different skip distances
Archive : Select dates in past to recreate Live Data display
Compare : Compare foF2 today with another selectable date (i.e. what was last week’s net like)
Averages : Building up list of historical averages for previous complete months
Data Credits : Acknowledgements and data sources
User Guide : Notes for Radio Amateurs
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