The choice of antenna (or, really, its pattern) affects what paths VOACAP
selects. As Guy has pointed out, VOACAP is aimed at broadcasters who want
the minimum number of hops, and favor low angle paths. VOACAP might indicate
that a low angle is preferred (because the antenna has decent gain at low
angles), when, for a real installation, with more gain up high, the multihop
path might actually be the one that gets used (even though it has more loss,
more dispersion, more variability and fading).
----- Original Message -----
From: "Bill Aycock" <firstname.lastname@example.org>
To: "Jim Lux" <email@example.com>; "Jim Lux" <firstname.lastname@example.org>; "Guy
Olinger, K2AV" <email@example.com>; "W3YY" <firstname.lastname@example.org>; "TowerTalk
Sent: Sunday, October 17, 2004 4:44 AM
Subject: Re: [TowerTalk] Take off angles, VOACAP, etcf.
> Is my intuitive logic wrong? It seems to me that the antenna has nothing
> do with the characteristics of the ionosphere; it only controls ones
> ability to accept and use the signals that are there.
> At 08:48 PM 10/16/2004 -0700, Jim Lux wrote:
> >I've been giving some thought to the VOACAP amateur radio thing..
> >If you run VOACAP, it displays the dominant path (and it's takeoff angle,
> >which is presumably what N6BV used in building the statistical tables).
> >However, I wonder what antenna was used. If it was an isotrope, all paths
> >would be weighted evenly in the selection, which will tend to favor the
> >angle one hop path, as opposed to the high angle two hop path.
> >If you give VOACAP a realistic pattern typical of most ham antennas,
> >have terrible gain below a few or 10 degrees, that might favor the high
> >angle two hop path, which would account for Guy's comments.
> >See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> >Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> >any questions and ask for Sherman, W2FLA.
> >TowerTalk mailing list
> Bill Aycock - W4BSG
> Woodville, Alabama
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list