25 Nov 02 5400kHz

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5417kHz 25 Nov 2002.bmp (97254 bytes)

This is a rather typical plot for 5MHz at this time of year. The plot starts at about 2230 and the band is effectively closed for this 80km path. The horizontal line at just above 0ms is slightly mysterious, it may be the groundwave but if so, I am surprised that it is detectable at 80km. The weak and rather blurred returns between 5 and 10ms from 0100-0600 are backscatter. As the sun rises on the F layer propagation rapidly builds at about 0740 and in just a few minutes, strong signals are back from the F layer - it would be interesting for a couple of stations about 80km apart to be on the air at this time to see this in action. Throughout the day, F layer communications continues. Multiple paths are always present, with less around local mid-day - possibly due to increasing D layer absorption. Just before 1500 the number of multiple returns increases (tying in nicely with yesterday's plot) and at just after 1800, the band dies abruptly leaving a bit of backscatter and the "groundwave".

6987kHz 27 Nov 2002.bmp (97254 bytes)

The plot above was done on 7MHz a day after the previous plot. The shape is very similar but, as I would expect from a higher frequency, NVIS starts somewhat later 0815 compared to 0750 and finishes earlier, 1720 compared to 1810. The pronounced "moustache" effect at the beginning and end of the NVIS period is caused by backscatter from the rapidly approaching skipzone. The slope gives the speed of approach which is about 840km/hour. As before, the mysterious "groundwave" remains all day.


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