Hi Roelof, thanks for those comments, very interesting. Yes the "multipath"
fading can vary quite noticably over area of around 20km. If the fading
period is faster you can see the same shape but time shifted. At the peak
you rarely get more than 6dB enhancement (two equal strength paths in phase)
but when they go out of phase the cancellation can cause the fade to be very
deep.
The Colorado Uni site.....note it plots Kyoto as well
http://lasp.colorado.edu/space_weather/dsttemerin/dsttemerin.html
Alan
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----- Original Message -----
From: "Roelof Bakker" <[email protected]>
To: <[email protected]>
Sent: Thursday, July 19, 2012 9:20 PM
Subject: Re: LF: Re: Kyoto Dst question
Hello Alan,
What might be interesting if you could classify the path length of
different paths (It depends whether you can find sufficient at the right
range) It would be interesting to try and correlate the excess path loss
against "hop number". I feel that if 1 hop has 6dB excess attenuation, a
3 hop path (5000 to 6000 km) should show around 18dB
<<<
I have noticed a phenomenon that might be less obvious when monitoring a
single station.
Propagation can be very selective in regards to geographic location.
E.g. there are quite a few NDB's in New Foundland. It is not rare to hear
one station with a good signal, whilst an other station is completely
absent. This also applies for the receiving end. There are many stories of
people living 20 km apart, where one has excellent reception and the other
does not hear anything at all and vice versa.
Last January we discovered a path to the North Bank of Alaska. This was
NDB PVQ on 376 kHz. The path opened in the middle of the afternoon in the
UK and extended to Normandy. At the same time I could not hear PVQ at all.
However half an hour later it was audible in Middelburg and gone in the UK
/ Normandy. After a break of a few hours it faded up again and was audible
all night with at times an amazing strong signal.
An interesting aside I spotted might be of interest to you. It regards
daytime skywave so a path of about 1200 to 1400km. I found that the
"precipitated" hot electrons from a big event were sufficient to give a
kind of prolonged "flare effect". The increased signal during a flare
event is due to he increased D-region ionisation. Similarly the increased
ionisation due to precipitation can enhance the daytime skywave signals.
The reports I have seen suggest the signals are most clearly enhanced
around mid day at mid path. The effect is often only present for about
one or at most two days after an event.
<<<
I have observed this on more than one occasion. In this case it was NDB
KEM on 373 kHz from Kemi, Finland, about 2000 km away. It was found that
reception at noon was a bad omen for nighttime DX propagation.
I guess that it will be difficult to use NDB's for accurate propagation
studies. However they are certainly useful to find some trends.
A Italian listener received on July 6 a number of faultless decodes on
NAVTEX on 518 kHz from VCO-Sydney, CAN NL, whilst on vacation on the
southern tip of Sardinia Island. This was probably a first for summer. It
is interesting to note that the DST at the time (02:45 UTC) was above 0!
In one of your latest emails you mentioned the Dst value from Colorado
University. I have searched the Internet, but could not find the data. Do
you have a link?
73,
Roelof, pa0rdt
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