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Yes Alan, I also think the "dome", due to
strongest D-layer ionisation around local noon, is the essence of good
daytime skywave LF and VLF propagation.
Loran-C observations seem to show that though the
maximum is much shorter during the winter season, it is not necessarily
weaker. I wonder whether increased sunlight intensity during January earth
perihel might somewhat counteract lower solar elevation... If so, Southern
latitudes should experience significantly stronger daytime propagation
during their summer than we do in ours.
73, Markus (DF6NM)
Sent: Thursday, June 26, 2014 3:08 PM
Subject: LF: Re: RE: Summer Solstice Test report
Hi
Mike well at 137 the daytime signal is skywave over about 700km I
watched Budapest (about 1200km) and there is a distinct "dome" in the
response at local noon at mid path. This is higher in summer as the sun is
higher and so stronger. I think on 472 the ground-wave is shorter
particularly at our power and aerial situations, and I suspect the skywave
though there may not be as predominant as at 137. .....more day-time
absorption. I am sure the local environment, trees building etc has an
effect too.
Alan
----- Original Message -----
From: "Mike
Dennison" <[email protected]>
To:
<[email protected]>;
<[email protected]>
Sent:
Thursday, June 26, 2014 12:43 PM
Subject: LF: RE: Summer Solstice Test
report
> On 25 Jun 2014 at 21:55, Alan Melia
wrote:
>>
>> It is interesting that there does seem to be a
suggestion that 137
>> holds up better in summer than 472.......have I
read that correctly,
>> or maybe it was from another poster. I was not
able to do the same
>> sort of tests for 472.
>
>
> I
haven't done any scientific tests, but from a lot of monitoring it
> seems
that for daytime ranges around 500-1000km 136kHz works better
> than
472kHz. I presume this because the 136kHz daytime propagation
> over this
distance is primarily by ground wave, whereas on 472kHz the
> ground wave
range is less so sky-wave is needed and this is not
> available until
dusk.
>
> It is difficult to compare the two bands over longer
distances
> because 472kHz is not available in Russia (unlike 136kHz),
and
> activity seems low in many other countries.
>
>
Personally, I have been disappointed by the amount of DX received
> during
darkness hours on 472kHz so far. It seems commonplace
> to receive
stations out to Scandinavia and Italy, but little beyond.
> Yes, I have
seen some transatlantic DX but nothing to match
> the stories of worldwide
openings reported by retired marine 500kHz
> operators, or indeed what is
availalable routinely on 160m. Is this
> just lack of
activity?
>
> de Mike, G3XDV
> ============
>
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