There's a 20-foot threshold, so at 7 meters the tool must have started
looking at the other numbers. I think the main difficulty is that the ground
level at my site is 251 feet and the ground level at the runway is about 16
feet, and that affects the calculation probably more than the proposed tower
height. TOWAIR doesn't claim to be all that accurate; there are caveats all
over the tool. But it didn't have any trouble calculating my horizontal
distance from NAS Whidbey, and because of the heights I'm in the area, I'm
going to need to apply.
I've already applied to the FAA for the highest planned tower. Hopefully
they'll consider the tree height all around and be happy that I'm not
proposing to go up much above the tree cover. Being on a high bank
waterfront makes for lower (and cheaper) towers. N6BV's HFTA is a great
tool to understand how this works.
It appears that I might have to make separate applications for the HyTower
and even the 50 foot push-up mast I have lying around. Once the main tower
is permitted, I hope the others will go more quickly and at some point
they'll ask me to stop applying.
We do have low flying aircraft over the property often, so common sense
suggests that anything that sticks up above the tree cover be evaluated as a
possible new hazard.
I haven't been there long enough to get tired of the aircraft noise yet,
although some of the locals are. It's still cool when a P-3 or EA-6B flies
by low enough to see the pilot. My Dad was career Navy; I spent some time on
three different aircraft carriers in my service years in the Navy, and
whenever I have a chance to see the Blue Angels, I go. I'm told that they
will be phasing in a new F-18 variant for the ECM mission, so we'll see (and
hear, and feel) fewer EA-6Bs and more F-18's in the future. Cool!
[mailto:email@example.com] On Behalf Of Pete Smith
Sent: Saturday, April 03, 2010 4:06 AM
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] TOWAIR query - proximity to airport, FCC and FAA
This sure suggests a computational error in the TOWAIR routine - like
when you do a model in HFTA and a 1-meter change in antenna height
produces a big change in pattern. I think the first thing I'd do is a
manual computation based on a topo map. Measure the distance from the
nearest border of the airport (for a conservative calculation), your
site's altitude, and apply the algorithm given in the FCC reg.
73, Pete N4ZR
The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
On 4/2/2010 6:26 PM, Dick Dievendorff wrote:
> At 6 meters of tower height, I don't need to register. At 7 meters of
> I'm suddenly 22 meters too high for the distance from Whidbey NAS.
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