[NLRS] RE: [Mw] Great Lakes Propagation

Mon, 29 Sep 2003 13:53:38 -0500

Hi Steve,
A number of us from the Northern Lights Radio Society (Minneapolis/St.Paul,
MN) have been looking at this re: Lake Superior for a couple of years now.
We have seen exactly the same things, and come to pretty much the same
conclusions (although there are differences of opinion, of course.)

A number of us operated across western Lake Superior the first weekend of
the Contest: seven on the Keweenaw Peninsula of Michigan and between 10 and
12 traveling the North Shore of Minnesota.  Conditions were, to say the
least, very, VERY, good.  Approximately 150 mi (240km) Qs with open
waveguide.  Q's with stations whose signals were reflecting off of the
granite cliffs along the North Shore (again, 150 mi+ paths, and totally
obstructed on direct headings.)

We had tried some of these same paths for the Contest in September 2002 with
less than good results.  A storm system and cold front had moved across Lake
Superior over night.  I was still between Duluth and the Keweenaw when the
contest started.  The entire morning resulted in maybe 2 Qs.  By noon
(local), conditions ahd settled down, and the evaportion duct reformed.
S9+20-40 signals were the only ones we heard !!  At the end of the day, we
again attempted the 200 mi path between Mt. Brockway and the bluffs above
Lake Superior at Duluth (~600' above the lake at both ends.)  One VERY
DIFFICULT CW Q was made, but it took an hour.  30 minutes before, 12 miles
NE, and 600 feet lower down, we had made S9+20 Qs without bothering to peak
the antennas!

Below are some URLs that have related material.  I've got a couple of others
a little less "technical," but I can't find them at the moment... I've got
hard copy somewhere that will have the URL on it... I'll have to find the
hard copies.  This stuff may be of some help/use to you. 

Good luck!

73 Donn
WA2VOI/0

http://www.cira.colostate.edu/GeoSci/Bacimo2000/paper/paper/paulus2.pdf

http://www.atmos.umd.edu/~carton/pdfs/babinetal97.pdf

http://www.weather.nps.navy.mil/~psguest/OC3570/CDROM/summer2002/Kuehn/repor
t.pdf

http://www.ips.gov.au/IPSHosted/NCRS/wars/wars2002/proceedings/comm-f/print/
kerans1.pdf

http://www.spawar.navy.mil/sti/publications/biblio/EVAPORATIONDUCTS.HTML
BIBLIOGRAPHY!!

http://www.nrl.navy.mil/content.php?P=02REVIEW99

Great Lakes buoy locations  (for data collection...)
http://www.nodc.noaa.gov/BUOY/bgl.html

>-----Original Message-----
>From: Steve Kavanagh [mailto:[email protected]]
>Sent: Sunday, September 28, 2003 8:07 AM
>To: [email protected]
>Subject: [Mw] Great Lakes Propagation
>
>
>During the second weekend of the 10 GHz & Up Contest
>we seem to have had quite enhanced propagation over
>Lake Erie between low-elevation lakeshore sites
>(S-meter-pinning signals on 10 GHz with 1W at 85-115
>km and a QSO made at 94 km with 50 microwatts on 24
>GHz).  At the same time, NE8I reports poor conditions
>at the North end of Lake Michigan. 
>
>This prompted me to think about what the mechanism for
>the extremely strong signals that we get from time to
>time on both lakes may be.  It may happen on the other
>Great Lakes, too, but I have no data.  I am suspicious
>that it may not be the traditional tropo propagation
>that we all know and love.  This is because
>traditional tropo (at least the surface-based kind
>useful for QRP non-mountaintop microwave contacts) is
>best at night and in the early morning, while the
>propagation observed over Lake Erie can be just as
>good in the late afternoon (that 24 GHz QRPp QSO was
>made at 4:17 PM).  WA8WZG once commented that it
>seemed to be better after the morning fog had burned
>off.
>
>One possibility is evaporation duct propagation, which
>exists at some level all the time over water, but
>works best under windy, low humidity conditions.  From
>what I have read I would expect this mode to be most
>useful at 10 GHz, and perhaps 5.7 and 24 GHz, but with
>rapidly decreasing effect at lower frequencies.  This
>mode is not well known by amateurs and there is not a
>whole lot published about it.  One reasonably good
>reference is R.A.Paulus, "Practical application of an
>evaporation duct model", Radio Science, July-Aug 1985.
> No, I don't know of any material on this propagation
>mode that is written for the layman !
>
>I have started to gather some material on the weather
>conditions for any days that I have observed to be
>particularly good or particularly bad at 10 & 24 GHz.
>However, that adds up to just 2 clearly good days and
>2 clearly bad days so far, which isn't much of a data
>sample.  I would be interested in any data others
>around the Great Lakes may have, with regard to what
>days and over what paths they may have observed
>partcicularly good or particularly bad propagation
>between lake-level (say less than 100 ft above the
>lake) lakeshore sites over beyond line-of-sight
>distances.
>
>Observations from similar coastal paths might be of
>interest, too.
>
>Can anyone help ?  Any comments ?
>
>73,
>Steve, VE3SMA
>
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