----- Original Message -----
From: "Pete Smith" <firstname.lastname@example.org>
To: "Jim Lux" <email@example.com>; "Stephen Reichlyn"
Sent: Tuesday, January 18, 2005 11:00 AM
Subject: Re: [TowerTalk] horizontally polarized antennas and salt water
> At 11:21 AM 1/18/2005, Jim Lux wrote:
> >Pete Smith wrote:
> > >
> > > It does, but not a bunch.
> > >
> > > I quickly modeled a 40m yagi at 104 feet over average ground versus
> > > water. Forward gain went from 11.86 dBi (avg) at 18 degrees to 12.45
> > > (salt). Takeoff angle, interestingly, went up one degree for the
> > > ground plane. Moving the antenna down 6 feet over salt water moved
> > > takeoff angle up 1 more degree, from 19 to 20 degrees.
> > >
> >Just as an idle question.. I wonder if the gain change is due to a
> >shape change (narrower main lobe), or due to a reduction in losses. The
> >average gain number would tell you, since it's integrated over all look
> It appears to be reduced losses. The average gain over salt water
> dB; over average ground it is -0.96 dB, per NEC-2.
Very interesting...In fact, the directivity is less with the salt water...
The difference in foward gain is about 0.5 dB, but the difference in loss is
0.9 dB, so the "extra" 0.4dB must be going into making the main lobe
All in all, though, such a small difference that you'd never see it in real
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