Propagation on 10 & 15 meters during the summer months..

[Juancho]

I'm on the equator in South America at an elevation of 3000 meters and have a question concerning propagation on 10 and 15 during the summer months (North America).

The first part if this year the higher HF bands (10 & 15) would open early in the morning (14:00 UTC) into Europe, mid day propagation would shift to North America and early evening again to southern South America and the South Pacific. Sometime around the summer solstice this year I noticed that this pattern was shifting, the bands opening later and later each day as the summer up north progressed. Decent conditions were also dropping off fast even though at times the flux was still fairly high. For instance today (at 19:00 UTC) the SSN is 169 with the flux is at 155 and I'm not really hearing anything other than week signals from the Southeastern US. Around the first of the year, with these numbers, 10 & 15 would have been wide open from 13:00 to 01:00 and I would have been hearing good signals out of Europe in the morning and the South Pacific until late evening.

I know there are seasonal shifts on these bands but, I'm just not finding a lot of information about them and little of this is reflected in the forecasting software I've been using. For instance what causes these changes, when can I expect them, etc..

If anyone could provide any information it would be appreciated.

Thanks

[ku4a]

When Tomas sees your post, he will be able to give you a much better answer than I can.

In general, here in North America anyway, summertime generally brings less DX on the upper bands. Local noise due to thunderstorm activity increases, and the extra hours of sunlight means that the D-layer of the ionosphere is more absorptive.

Sproadic-E does provide some short-skip in this frequency range during the summer. I understand from my research that Es is much more prevalent the closer you get to the Equator. For a 6m fan like me, it must be a lot of fun.