[TowerTalk] tower height repost

[Steve W3AHL]

The arrival angle data for HFTA (and VOACAP) are limited to 30 MHz  max. 
However HFTA's ray tracing seems valid at 6M  (for 2M I suspect the spacing 
interval of the radial plots would need to be decreased).  So at least you 
could see how antenna height interacts with surrounding terrain in critical 
directions.

If you want the radial elevation plots for your location (needed to use 
HFTA), send me your latitude and longitude in decimal degrees to at least 
four places (DDD.dddd with N, S, E W) and I will e-mail you a zip file with 
the radials plots, if you don't want to learn to use MicroDem to generate 
them yourself.  If its for 6M use I could decrease the sampling interval to 
half the distance used for lower bands.

For 2M coverage it is probably better to use Radio Mobile with 1/3 arc 
second DEM's of your terrain, although that's not so useful for DX coverage.

Steve, W3AHL

>I don't know if HFTA has any arrival angle data for 6M.  It's
>predecessor YTAD did not.

>Without arrival angle data how would you know some antenna height change
>is good, bad or indifferent.

>I seem to recall Es prop (at least for 1 hop) is relatively high angle.
>If this is what one is after, then lowering rather than raising the
>antenna is a better idea.   Many 6M ops find 20-25' works pretty well.