This page is a 'primer' for PARC members. It is 'work in progress' and liable to have significant changes.
Please use it as a starting point for your own investigations.

VHF Propagation

Tropospheric Ducting Forecasts

  Mountainlake APRS Tropospheric Conditions
Near Real-Time (Link)

Currently unavailable (Nov. 2018)

VHF/UHF Area Prediction Tool
Online modelling application for local terrain  (incl. knife-edge refraction) Go to the website and enter a location and various parameters for a prediction of the likely path losses. Link:

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.

Enter a location and various parameters for a prediction of the likely path losses. Link:
This is a complex subject so please do your own research.

Example Tephigram for Nottingham 28 December 2016 Nottingham 1200Z

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

Click to enlarge

Data source: Weather Online. Diagram from Leeds University.

Sources of Daily Tephigrams

Daily charts for several places in the British Isles are available on the following websites:


HF Propagation

Global Ionospheric (Critical foF2) Conditions Today (Live)


Hourly Area Predictions Today (Live)
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 Today (Live)
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 Meteorology. 


Current British & Global K & Kp Geomagnetic Indices Today (Live)

Recorded at UK Observatories by the British Geological Survey

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


G3YLA Real Time Propagation - Today (Live)

A very useful interactive website provided by Meteorologist Jim Bacon G3YLA - This site includes foF2 observations from Chilton & RAF Fairford (UK) and Dourbes (Belgium). The additional stations give a broader picture of conditions across the UK and the 'Lowlands'.

However, there is a problem with the new upgraded site with the sizing/scaling of the chart which can make it cluttered and virtually unreadable.


Spaceweather Conditions
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

K & A Indices give a 'health check' on the geomagnetic stability of the ionosphere. /font> 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 may 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).


Critical Frequency, MUF & Ionograms, foF2 & 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.

Example of an ionogram from UKSSDC Chilton

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

Annotated hypothetical example ionogram

Explanation of Ionograms

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.

Longer explanation of ionograms

 See the UKSSDC explanation (click the diagram or go to

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 & IO92 (Central England) showing seasonal and year-by-year variations

NB - very large image


UKSSDC (Chilton) Ionosonde Data

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.


Propagation Predictions


This up-to-date application produced by the ITU is the successor to the VoACAP Propagation Prediction suite (see below). 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.  The ITURHFProp program incorporates current information about prevailing solar trends.


VOACAP (Voice of America Coverage Analysis Program)

This has been overhauled recently to make it much more useful. 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.


Space Weather

Space weather is an increasingly 'hot' topic. Some aspects are complex, but there are many websites available: start at:

European Space Agency

Space Situational Awareness

Of particular interest is this ROTI diagram showing ionospheric disturbance over Europe:



Current images of the sun. Look at the AIA 193Å image on the FAR SIDE tab.


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:


European Digital Upper Atmosphere Server (DIAS)
(Registration required)

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