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Dear Carl,
many thanks for your answer. I realy appreciate your time and effort to find
an explanation.
The word document arrived also OK and it's very usefull.
73 Ady YO2NAA
-----Original Message-----
From: propagation-bounces@contesting.com
[mailto:propagation-bounces@contesting.com] On Behalf Of Carl K9LA
Sent: 29 martie 2008 00:26
To: propagation@contesting.com
Subject: [Propagation] YO2NAA to W7 on 20m
Ady,
I saw your 24 March posting about your unusual 20m propagation to W7
(specifically K7RL and W7WA) at 2140 UTC on February 17.
Thomas KN4LF offered a very plausible explanation, but I see another
possible mechanism for your two QSOs - propagation along the true short
path with help from Es (sporadic E).
In a personal e-mail (since I believe this reflector can't handle
attachments) I sent you a Word document with a worldwide map of median
MUF(3000)F2 at the time of your QSOs. It also depicts your short path to
W7. Additionally this map identifies the Juliusruh (54N/13E),
Sondrestrom (67N/51W), and the Qaqanaaq (77N/70W) ionosondes, with F2
data and Es data from all three.
As you noted, the F2 MUF on your end of the short path was just too low.
This is also confirmed by the Juliusruh ionosonde, which is fairly close
to this path.
You also noted you saw Es at the Belgium ionosonde that could support
14MHz, and this is also seen in the Juliusruh ionosonde. So it's
plausible that the beginning of your short path to W7 was supported by Es.
This gets your RF into the polar cap, where the median F2 MUF is
predicted to be way too low. The Sondrestrom ionosonde (south of the
path) shows high enough F2 ionization earlier in the day, with some
spikes seen around the time of your QSOs still high enough to suggest
that F2 may have been possible. The Qaanaaq ionosonde (north of the
path) doesn't show sufficient F2 ionization at any time.
Both Sondrestrom and Qaanaaq show sufficient Es to extrapolate that
there may have been enough Es in the polar cap around the time of your
QSOs to support 14MHz.
Thus your QSOs may have been via sporadic E along the short path until
far enough west to encounter the higher F2 region ionization on the W7
end of the path (the predicted F2 MUFs on the W7 end, as can be seen on
the worldwide map, are well above 14MHz).
Since you used a dipole (for the most part omni-directional - except
with nulls off the ends), your antenna really doesn't provide a clue as
to which explanation is most likely - KN4LF's skewed path hypothesis to
your southwest or my short path hypothesis to your northwest via Es and F2.
So I e-mailed K7RL and W7WA and asked them which way their antennas were
headed. I received a reply from K7RL. My e-mail to W7WA bounced.
K7RL has a three-high stack of Optibeams (each has four elements on
20m), and he was pointed to 40 degrees - which is along the short path
to you. He also said "conditions were quite good with many EU signals
well into the afternoon." Thus it is likely that your QSOs were via the
true short path using Es on your end of the path and in the polar cap
and F2 on the W7 end of the path.
Carl K9LA
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