[CQ-Contest] Contest QTH

Pete Smith n4zr at contesting.com
Sun May 23 06:44:19 PDT 2010

I hope that Dean will chime in here, because I recall an e-mail 
conversation a few years ago in which he said he felt that About 3 miles 
was a practical limit.  I once built a terrain file that had too many 
points for HFTA to process, which suggests to me that you need a 
compromise between the range covered and the amount of detail in the 

My trig is way too rusty to attempt the math, but if you start with an 
antenna at a given altitude, go out 15 miles and identify a point that 
is maybe 500 vertical feet above that plane, and draw a line between 
them, as well as a horizontal line (we're talking flat earth here 
hi)from the antenna to the obstruction, what angle above the horizontal 
will just clear the ridgeline?  I know the number is pretty small, just 
not *how* small.

73, Pete N4ZR

The World Contest Station Database, updated daily at www.conteststations.com
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On 5/23/2010 12:47 AM, David Gilbert wrote:
> Hi, Pete.
> I don't think there is any kind of formal limit in HFTA.  The terrain
> slopes rapidly down eastward from my QTH at roughly 15% for about a half
> mile, maybe 8-10% after that for a couple of miles, and then about 4%
> for the next five miles.  After that it starts sloping gently upward for
> a few miles before hitting a mountain ridge line about 15 miles away
> that is just a bit higher than my QTH.  I've compared terrain files with
> and without that distant ridge line and the impact is definitely
> noticeable at low angles.  Granted, HFTA says my particular QTH puts out
> a lot of energy at very low angles (the major peak is at 2 degrees), so
> maybe 4,000 meters is a practical maximum horizon for a more typical
> terrain, but I don't think the program constrains itself to any
> particular distance.
> 73,
> Dave   AB7E
> On 5/22/2010 2:44 AM, Pete Smith wrote:
>> HFTA only uses terrain out to about 4000 meters.
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