[TowerTalk] 80 mts four square or yagi? (HFTA)

[Ed Sawyer]

Don't be afraid to actual do your own survey for the first part.  For 80M,
the "near field" which usually defines 90% of the terrain effect unless you
have a HUGE drop off past that or a HUGE hill blocking you past that is 5
wavelengths or 400M.  That's not too hard to do a pretty accurate estimate
of your own topography and then let the larger data tools take over from
there.  

 

HFTA defines a "ray" or a literal straight line to the area of interest.
You need to record a file that says what the elevation drop or rise from the
base of the tower or the ground right under the antenna all the way out to
10,000 Meters. But you will find if you play with the data that the data
beyond 1000M doesn't effect it much unless there is a big obstruction out
there.

 

I took my own pretty accurate survey data to EU, JA, PAC, and SA for my
towers out about 500M.  The accuracy of the modeling that I see in real
practice is superb.

 

Ed  N1UR