[TowerTalk] Ground Constants

[Brian Beezley]

To better represent specific terrain, my HF Ground Constants page now 
includes an interpolator for the Hagn generic curves. The Hagn HF values 
are more realistic than the ARRL ground constants offered by antenna 
analysis programs, which are actually for the AM broadcast band:

http://ham-radio.com/k6sti/hfgc.htm

I've updated my ground probe calculator and the utility that averages 
ground constants in time or space:

http://ham-radio.com/k6sti/gnd.htm

A 1934 paper sampled soil at depth at a dozen locations in Great 
Britain. The paper provides enough data to determine the accuracy of 
short ground probes. Errors of tens of percent at 10 MHz are common, 
with a few much higher. Errors were < 30% for a trench in Oregon:

http://ham-radio.com/k6sti/gpse.htm

To avoid ground probe sampling error, I took another look at the low 
dipole method of measuring ground constants. This method samples ground 
at the proper depth. However, it provides ground constants only for a 
single band. To overcome this limitation, I tried extrapolating results 
to the other HF bands with the Messier soil model. It works remarkably 
well. See the documentation for more:

http://ham-radio.com/k6sti/extrap.zip

Brian