Sunday 28 July 2019

Propagation models: what's the point?

Early this morning, from 03-04UT, I couldn't sleep, so did some operating on 14MHz.

Despite the poor solar conditions, I was getting deep into Russia, with a fair number of stations from the M and N grid regions, and the occasional O grid, too.

This is how the FT8 signals were coming and going at the time.  Notice the small number of stations on the far West Coast US hearing my 35W from a vertical delta loop (this propagation was extremely transient, lasting only a couple of minutes):


Now look at how ITUprop was predicting 14MHz, assuming 100W to a dipole as the transmitter (a lot more power than I was using, but a similar overall antenna):

By any standards, that's a very poor model of propagation.  In essence, it's simply telling us that, in the early morning of late July, propagation is broadly and weakly to the east.  In other words, it's telling us nothing at all.

Unfortunately, I failed to select the correct sound input for HRD, because there was an R8 station, and some others, showing very strong echoes, indicative of a combined long and short path propagation at the same time.  I'll catch those sounds again tomorrow morning!

1 comment:

John, EI7GL said...

Hi John

I suspect the propagation models are based on solar data like the approximate sunspot number. The huge variable is of course Sporadic-E during the summer months which can't be forecast.

Perhaps they are more accurate during the winter?

John, EI7GL