[VHFcontesting] Climate input used in SPLAT!

[James Duffey]

Paul - Yes, you are correct and I alluded to that in my original post:

> 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 original SPLAT! Linux program has the ability to change between 5  
or 6 climate models, including the temperate one that is used in the  
web page, it also includes a tropical one, desert one, and a coastal  
one. I would like to see the desert one implemented as those are the  
conditions we most likely encounter here in NM.

The program is probabilistic and is based on what is essentially an  
empirical model. So the numbers it calculates are for 50% likelihood  
of occurrence. One of course waits for the 50% when the path loss is  
less.

The Linux version does offer the opportunity to change the climate  
model. But it also requires one to download and process an extensive  
database. The web page based calculation is straight forward and less  
frustrating to implement.

I realize the limitations in models. They certainly are not to be  
blindly followed. But they are a useful tool and in my case I find  
SPLAT! to be useful in identifying good spots to rove from and also to  
see how the coverage will change when I change antennas or power. In  
particular, incorporating terrain into the model helps immensely in  
NM, as we are far from flat and the conventional approaches such as  
the graphs in the handbook are not too useful. I certainly did mean to  
imply that SPLAT! is an exact calculation and if I left that  
impression I apologize to you and the list.

This brings to mind a quote that I refer to often in my work:

"Nobody believes the model except the modeler; everybody believes the  
experiment except the experimenter."

I will try "impossible" paths when I rove, and I have made a few. But  
with some knowledge of what to expect, I won't expend a lot of effort  
trying that path when there are others to work on paths with less  
loss. In NM during contests we usually have lots of time to try  
difficult paths though.

I hope we can work in June on Sporadic E. See you then. - Duffey
--
KK6MC
James Duffey
Cedar Crest NM