Are you wondering why you very rarely hear UK stations on 40m nowadays?

Important things to remember about propagation:
(1) it is always changing - by the minute, hour, day, week, season, solar cycle, etc
(2) it
is affected by many natural phenomena and therefore is very difficult to predict
(3) different places will have different propagation, even at the same time
(4) most explanations of propagation in radio books are over-simplified generalisations
(5) bigger antennas or higher power levels do not change poor propagation.

The more you learn about propagation the more you will realise that there's even more to learn - mostly through experience.

NB this page is principally for PARC members' self-training - it is constantly reviewed and revised.

Current Global Ionospheric (Critical foF2) Conditions

Near-Real Time (hourly)


Hourly Area Predictions (Current)

Near-Real Time

This HAP Chart produced by Space Weather Services, Bureau of Meteorology, Government of Australia gives a near-real-time view of the f0F2 conditions affecting the UK (London).

For fuller information please visit the webpage (link) where you can select other locations.

HAP Chart © Copyright Commonwealth of Australia 2016, Bureau of Meteorology

Local Area Mobile Predictions (Current)

 This LAMP Chart is intended for use by UK Cadet Forces [presumably for 5MHz portable communications]. While precise data may need to be re-interpreted for Amateur Radio use the general principles do apply and illustrate changes on useable frequencies during the day.

For fuller information please visit the webpage (link) where you can select other locations.

LAMP Chart © Copyright Commonwealth of Australia 2016, Bureau of Meteorolog

Current British & Global K & Kp Geomagnetic Indices

Recorded at UK Observatories by the British Geological Survey

Please visit the BGS Page:
'Current geomagnetic activity in the UK and across the globe'

Current UK HF Band Conditions

Example data - click image to go to the website

This website is provided by K1BIZ with data from an un-named source which provides "HF Ionospheric Interferometry" using a methodology which is not described.

It is unclear how information about UK band conditions is generated so the snapshots may need to be treated with caution.

UK Meteorological Office

The Met Office provides a concise synopsis of prevailing and forthcoming spaceweather conditions

Example (Geomag Impact Scale)
(c) Crown Copyright / The Met Office

Please visit

 Note on K & A Indices

 A Note on K & A Indices

  • K & A Indices give a 'health check' on the geomagnetic stability of the ionosphere.
  • As a general rule, lower values indicate more stable conditions which usually lead to 'better' (more predictable) MF & HF conditions. 
  • 'K' values represent an average of rolling 3 hourly measurements at specific locations; 'Kp' values are similarly obtained but values are averaged across the globe. So, K / Kp values indicate the extent of hourly fluctuations in the earth's geomagnetic field (see note below).
  • 'A' values indicate the daily trend in geomagnetic variations. They are an average of eight 'K' values: that means they are a 24 hour rolling average. 'Ap' values are average values for the globe.
  • Together, K & A (Kp & Ap) Indices indicate the 3 hour vs 24 hour fluctuations in geomagnetic conditions.  Values of less than K = 3  and A = 6 indicate 'settled' conditions that give good propagation.

The British Geological Survey also produce a K(UK) value is a daily average of indices measured at 3 UK Geomagnetic Observatories (Lerwick, Eskdalemuir, Hartland).

foF2 / MUF Ionosonde Data

The UK Solar System Data Centre (see below) produces real-time ionosonde data every 10 minutes throughout the day using the UKSSDC Chilton Ionosonde.  An example is given below.

The ionosonde data is available in a number of formats including ionograms (see below) and tables. This information is very helpful in determining likely current HF propagation conditions across the UK and also helps work out the prevailing 'skip distances' for, say, 40m contacts. The conditions affecting other bands can also be deduced. As with other examples on this site, the information may need further personal research in order to fully understand what the data shows and how to best use it.

Real and hypothetical examples
click to enlarge

Example ionogram from Chilton

The horizontal axis is the frequency of the ionosonde sweep (MHz); the vertical axis is the height in km.

Annotated example ionogram

This example shows some small differences to the Chilton - see below

Short Explanation of Ionograms

Importantly for Radio Amateurs the ionogram chart (left) shows the prevailing critical f0F2 frequency (6.052MHz), and the calculated MUF at various distances (D vs  MUF at the bottom). 

The coloured lines/zones represent electron densities at different heights (vertical axis) and the horizontal axis is the frequency of transmission by the ionosonde. The curves and cusps on the lines indicates zone of reflection and the values are used to compute the tabular information on the left hand side of the chart. The tabular information is primarily what we are interested in.

Setting aside the lines and curves in the body of the chart, the basic conclusion that can be drawn from this example is that the critical frequency (foF2) at Chilton at 10.00UTC 4 Jan 2017 was 6.052MHz. Hence contacts on 40m with stations closer than 300-400km from a (nearby) UK transmitter were likely to be very weak and unreliable: however, stations farther away could have been workable. The higher bands (for example on the 20m band) may not have been reliable for contacts less than approx. 2000km) distance. So, the ionograms give an indication of conditions, but should not be regarded as conclusive evidence of actual radio conditions - many complicating factors may apply.

Longer Explanations of ionograms - best to read both

 See the UKSSDC explanation here
(see the note below)

Note: an asymptote is a straight line that continually approaches a given curve but does not meet it at any finite distance

Alternatively see this NOAA page:

Comparison of foF2 in 2015 & 2016

for IO91/2

NB - very large image


To access the Chilton ionograms registration is required. Use of the data for purposes other than research, or for re-publication, may require a licence. The Ionograms (and other charts) can be found at:

Registration can be done at:
UK Solar System Data Centre, Science and Technology Facilities Council
Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX

Example of Daily f0F2 Variations

1-10 January
Data from Chilton (UK) Ionograms illustrating unstable conditions.
The chart shows the average f0F2 critical frequencies (vertical axis / KHz) for 1000 to 1600UTC each day from 1 to 10 January (horizontal axis ~ days run left to right, top to bottom). Click to enlarge.

VHF Propagation - hints

Tephigrams for British Isles

Tephigrams are a vertical profile of temperature and dew point through the troposphere, taken by radiosondes (weather balloons), daily by the Met. Office at Watnall, England (and elsewhere).

The interpretation of tephigrams can appear complex and explanations are lengthy. If you are interested in the subject there are many online sources.

Here we present a link to daily tephigrams which we use to identify any temperature inversions that may result in enhanced tropospheric propagation - 'Lift Conditions' - at vhf (2m especially) over the East Midlands.

The things to look for on a tephigram are a sharp swings of the red line (temperature) to the right, which is usually associated with a sharp left-right swings of the blue line (dew point) indicating the tops and bases of cloud layers.

Temperature inversions at low or intermediate levels (900mb - 500mb / 2500 to 18000 ft) potentially give rise to 'Lift Conditions'. At much lower, or much higher, levels the effect may be less pronounced.

This is a complex subject so please do your own research.

Daily charts for other places in the British Isles are available on the following website:

Millibar / hPa Conversion (for Tephigrams)

Level mB / hPa Height ft Height m
1000 364 111
925 2498 762
850 4781 1458
700 9882 3013
500 18289 5576
400 23574 7187
300 30065 9166
250 33999 10366
200 38662 11787

Tephigram for Nottingham (example)

28 December 2016 Nottingham 1200Z

Shows temperature inversions at 110m, 3000m & 5600m.

Click to enlarge

 Data source UK Met Office via University of Wyoming.
Diagrams from Leeds University.

Links - Propagation Predictions


ITURHFProp - Propagation Predictions

This up-to-date applications is the successor to the VoACAP Propagation Prediction suite produced by the ITU. It gives predictions of path reliability based on 'standard' seasonal and daily variations - however these do not include short term variables such as geomagnetic storms and sunspot activity.

NB PARC only use this type of application as very general guide before checking out actual current conditions. As a purely predictive tool it may be more reliable than the original VoACAP, but superficially it doesn't appear to offer any tangible improvements.


VOACAP (Voice of America Coverage Analysis Program)

The original VoACAP application is still available online

It provides
predictions of path reliability based on 'standard' seasonal and daily variations - however these to not include short term variables such as geomagnetic storms and sunspot activity. 

Functionally it is very similar to the ITURHFPROP software but has a more useable interface, better tools and a much nicer interface in PARC's opinion.

NOAA Space Weather Enthusiasts Dashboard

A comprehensive set of tools provided by the

National Oceanic and Atmospheric Administration
Space Weather Prediction Center

Viewing the Aurora

A short explanation about when and where to see the Aurora Borealis

Northwest Research Associates
 Many useful plots together with on-page explanations. Features some nice comparative graphs - see this page:

Dourbes ionograms


European Digital Upper Atmosphere Server
(Registration required)