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Caveat for Slough Data

Early Data, 1930 - 1943

We have discovered scaled data sheets in our archive and have used it to replace the data which was in our catalogue for this period. The old data from our catalogue remains online. The new data is more numerous and it includes monthly medians. In addition, we have an accompanying caveat and usage guidelines (below) to give background to the immature nature of ionosonic sounding at the time.


Between 12th October 1936 and 29th October 1938, any foF2 with the value of 113 should be treated as erroneous. This systematic error is produced by a lowering of the maximum frequency of the sounder.

During the period these soundings were taken, there was less radio interference. Ionograms started at ~0.7 MHz and the E layer is visible much more - which is mentioned in early early publications.

Ionospheric History Notes

Richard Henwood
30th March 2004