CT2JKO - Ham Radio and Local Weather

View of Planet Earth - (http://www.fourmilab.ch/cgi-bin/Earth) :

Ionospheric Conditions - (http://www.ips.gov.au/HF_Systems):

This image shows the DIFFERENCE between current OBSERVED HOURLY conditions and PREDICTED MONTHLY conditions for the global ionosphere. The colours blue, green, yellow, red, correspond to "enhanced", "normal", "mildly depressed" and "depressed" conditions respectively. Depressions and enhancements are with respect to the IPS predicted monthly T index for that month.

Global:

Europe Ionospheric Map

Ionospheric Maps - (http://www.ips.gov.au/HF_Systems):

The map can be used as a guide to NVIS ionospheric frequency support and to generate real time HF predictions (eg Hourly HAP charts) to assist the HF radio communicator.

A feature of the ionosphere is its ability to reflect radio waves. However, only radio waves within a certain frequency range will be reflected and this range varies with a number of factors.

The most widely used instrument for ionospheric measurement is the ionosonde. The ionosonde is essentially a high frequency radar which sends short pulses of radio energy into the ionosphere. If the radio frequency is not too high, the pulses are reflected back to earth.

The ionosonde records the time delay between transmission and reception of the pulses. By varying the frequency of the pulses (typically 1-22MHz), a record is obtained of the time delay at different frequencies. This record is referred to as an ionogram.

The highest frequency which the ionosphere will reflect vertically is called foF2. These foF2 measurements from various sites can be used to create a map of foF2.

Global:

Europe Ionospheric Map

Current HF Fadeout - (http://www.ips.gov.au/HF_Systems):

During a solar flare, increased ionisation in the D-layer of the ionosphere can result in reduced signal strengths for HF circuits which are reflected by the ionosphere on the sunlit hemisphere of the earth. This is known as a short-wave fadeout.

The map above shows the absorption limited frequency (ALF) - the lowest frequency able to propagate - for HF circuits typically 1500 km in length. To use the plot, work out the approximate location where your circuit is being reflected by the ionosphere and estimate the value of the ALF from the contours. If the frequency you wish to use is lower than this value then communication is unlikely; if it is higher than the ALF then communication is still possible.

For short circuits compared with 1500 km, the ALF values from the map are likely to be too high and communications will still be possible for slightly lower frequencies. For much longer circuits, slightly higher frequencies than the suggested ALF can still be affected by the fadeout.

Europe Ionospheric Map