Path loss is not constant but varies greatly with?weather conditions. Such a
program likely assumes a loss number that is good for almost all the time.
Whereas vhf contesters work new grids by finding those times (often very short)
when the path loss is much less than normal.
73 Paul AA4ZZ
-----Original Message-----
From: James Duffey <JamesDuffey@comcast.net>
To: vhfcontesting@contesting.com
Cc: James Duffey <JamesDuffey@comcast.net>
Sent: Fri, 7 Mar 2008 8:42 pm
Subject: [VHFcontesting] SPLAT!
The ARRL internet surfer, WA1LOU, has just posted on the ARRL page an
interesting summary of a web page called SPLAT!:
< http://cs.ecok.edu/~bw/SPLAT/ >
SPLAT! calculates path loss for frequencies from 20 MHz to 20 GHz. You
input your location, antenna height, and frequency. It will calculate
a coverage pattern for you using the Longley-Rice Irregular terrain
model. It will calculate the path loss between two stations and
display the path loss as a function of distance between two stations.
You need to input your lat and lon and it adds it to a database of
other stations. You can calculate the path loss between any two
stations that are on the list.
This is a web hosted version of the LINUX program SPLAT!, with which I
was not familiar.
I entered a couple of my favorite rover sites and the results seem to
qualitatively agree with what I have experienced. The path loss
calculation lets you see what you need to do to work those stations
that never seem to come back to you. It also lets you evaluate
potential rover sites against working the usual contest suspects.
Using this you can calculate the effects of antenna height and sloping
ground.
The are a couple of things one needs to look out for, I noticed that
it calculates the path loss assuming vertical polarization and it
defaults to the temperate climate model. Assuming vertical
polarization probably is a few dB down on horizontal polarization for
troposcatter and in some locals a better climate model should be used.
The desert option would be nice here in NM. The Linux version allows
one to change these things, but you also need to download a whole lot
of terrain data that the web page author has already done.
Try it out, it is a great tool for planning roves. - Duffey
--
KK6MC
James Duffey
Cedar Crest NM
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