[UK-CONTEST] 40m to USA long after sunrise

[Clive Whelan]

Hi Gerry

<<

Did you mean to say the *daytime* F-layer?

 >>

Well not quite, if only because I had failed to ensure total engagement 
of my brain before allowing my fingers near the keyboard ;-)

I suppose what I really meant is that F layer refraction is not anywhere 
near the limiting factor that it is on higher frequency bands. Any 40m 
contest freak like myself ought to be aware of the dip in transatlantic 
propagation in the ( approx.) 03-04 slot, although as you say the big 
gun stations over there can always make things happen.

What I definitely did not mean to say was that the North Pole region 
could be in total sunlight after the autumn equinox. That was a senior 
moment in which I am well qualified!

 From what you say, my observations today were evidence of two 
simultaneous and opposing phenomena, viz E layer absorption at local 
noon and F layer enhancement at DX dawn. It is further interesting to 
note that the JAs and UA0s did not seem to dip to the same extent around 
local noon ( although I have to say that was a group of stations and not 
a single one like N8AA).

The polar path phenomenon may also be  known to students of 20m 
propagation, as the VE6JY effect. That is to say that in the major 
winter contests VE6JY (a mega station of course) is heard at our 
latitudes well before any US or VE East coast or e.g. FL stations which 
might indicate that the path is a polar skew one rather than a classic 
great circle one. It would be interesting to know if in fact we enjoy 
this enhancement  in preference to our Southern European neighbours who 
normally enjoy a  significant advantage  in transatlantic propagation, 
even more so on  21 ( and 28) Mhz.

As always in the field of propagation there are more questions than anwers.

Now can anyone really explain Es ;-)

73


Clive

GW3NJW


Gerry Lynch wrote:
> Clive Whelan wrote:
>   
>> What I did not expect however 
>> was that the signal would then climb significantly before local noon, 
>> and by 11:50 he was back up to 559.
>>     
> Sunrise in Hamilton, Ohio this morning was 1202 UTC.
>
> I don't agree with the comment in your other post that the F-layer will 
> support 7 MHz refraction at almost any flux level; it quite clearly 
> doesn't at high latitudes at night.  It's quite noticable how the Ws dip 
> after midnight here, especially as the winter creeps on, with only the 
> big guns and maybe W4s coming through, and the Caribbean and SA stations 
> dominating the band.  It's not a bad time for DXing, but a bad times to 
> try and run Dubyas in a contest.  Did you mean to say the *daytime* F-layer?
>
> Other than that, great post!
>
> 73
>
> Gerry GI0RTN
>
>
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