WSPR - More and More Questions.

Last night was the second 14MHz WSPR run, looking specifically at the propagation around the time of 'setting' of the sunlit F2 layer locally.

Bang on time, and with a couple of minutes' delay from the previous evening (superficially consistent with lengthening daylight), all US stations,all east or mid-southern states, took a dive in signal strength, promptly vanishing altogether at around 22:36UT.

That was the expected situation.  So far, so good.

Then the complications began.  After a few minutes, I started hearing - and was sometimes heard by - a station way, way out west in Alaska - AL7Q.  A couple of other west-coast stations were then heard - VA7UBC and N6RCD.  A station in the extreme west of Montana, right on the border with Washington state - WK0I - also was heard, and was also hearing me.  This is not the first time I've noted something special about WK0I.  There were only two EU stations also 'seeing' the same thing. and indeed the only ones in connection with the US at all from the EU.  One an ON station, the other a LA station, in the far north of Norway.

Whilst the rest of the US was silent both ways, these three, and one in Alaska, just kept going, long after the theory of propagation indicates it should have stopped.  The magnetic pole is a suspect...

 
Rather bizarrely, there was a short period earlier in the evening but after the disappearance of the F2 layer, where three, tightly clustered stations in or very near to Dallas, Texas, were the only ones hearing me.  These were K5XL, KE7A, and KD6RF.   I have absolutely no explanation why that was, especially when one considers, at a visual guess, that there were maybe 60 or more US-based WSPR stations active at the time, and with a good geographical spread across the country.

This bizarre, tight cluster were the only US stations hearing me for one, post-F2 layer period.

I suspect the late evening development of a path between me and the west-coast US had something to do with the magnetic field, given the northerly latitudes and proximity to the pole of all stations involved.  That said, whilst the LA station is in a special magnetic location, I'm not especially so, nor was the ON station.

Auoral conditions were quiet, with a very small increase in activity but still at very low levels.  I remembered something about paths tangential to the auroral oval, and something called the mid-latitude trough (of low ionisation), and one or both of these might have some importance for last night's path out west.

I need to read a lot more, but that often leads to more questions - and a realisation that nobody, really and truly, fully understands propagation under more esoteric situations.


As we move into spring and summer, this kind of exercise won't be possible much longer on 14MHz, so I'll keep going on this for a while, and later in the year.

If you've any insight, please leave a comment!  After a few nights of more activity, I can see that this strange reception of signals from out west is not a regular occurrence, with the whole of the US shutting down entirely on a typical night as the sunlit F2 drops below the horizon.