Propagation explanation needed

Old Reflector
1

OK, I’ll admit my understanding of HF propagation is simplistic. If you want some cool embedded software doing, then I’m your man, but this signals in the aether lark is voodoo. Every time I think I understand what is happening I realise I’m actually pretty clueless.

So yesterday I was on the summit of Ben Ledi. A short and sweet hill, 750m ascent in 3.5km made my legs complain after 4 weeks larding about! Anyway conditions on 40m and 60m were dire with a capital D. QSB was extremely rapid on 60m and I was quite a weak signal with the few I worked. 40m was rubbish too with just a few strong signals heard. Yet Shannon VOLMET was S9+++ an RAF VOLMET was S9. I worked Mike GW0DSP and he was a good S9+ but most other stations were not brilliant either.

When I checked the Chilton ionosounder it showed the foF2 was up to 7MHz when I was active. There was a sudden drop at 1500z but I was packing away to avoid an incoming rain storm then. Looking at the ionoshpere data services I normally use would suggest things should have been much better than they were.

So can someone with a deeper understanding of how this bouncing radio off the sky works please provide one very confused embedded software chap with some clue please?

Andy
MM0FMF

2

In reply to MM0FMF:

Hi Andy, you were a good signal here, so you certainly have me flumoxed.

Maybe John GW4BVE can put an explanation to what was happening, he has an excellent understanding of HF propagation, especially NVIS. Cue John?

73
Mike GW0DSP

3

In reply to GW0DSP:

I don’t know, but strange directional effects seem to happen on these bands when sporadic E is about!

73

Brian G8ADD

4

In reply to MM0FMF:

So can someone with a deeper understanding of how this bouncing radio
off the sky works please provide one very confused embedded software
chap with some clue please?

Not very deep, but basically it is the sun which is responsible of changes in the propagation. On July 12 there was small geomagnetic storm, but July 11 should have been quiet. I find the simple ascii list of K-index history useful

http://www.swpc.noaa.gov/ftpdir/indices/DGD.txt

with the present data that is used by the propagation prediction programmes

http://www.swpc.noaa.gov/ftpdir/latest/wwv.txt

73, Jaakko OH7BF/F5VGL