On Tue, 25 Apr 2017 15:11:46 -0700, (Dave
Platt) wrote:

In article , rickman wrote:

Interesting. Any idea what the specs mean?

Gain 3dBi
"Marine Gain" 6dB

I know what dBi is, but what is Marine Gain? Is there some reference
antenna they use such as the rubber ducky?

That's probably taking into account an assumed 3 dB of additional
gain, due to the fact that the antenna is located a short distance
above the water surface. Salt water is an excellent reflector of RF
energy. At certain angles and distances, the primary wave from the
antenna and the reflected wave from the water surface will be in-phase
with one another, and will reinforce, doubling the strength of the
received signal.

In other places the two signals will largely or entirely cancel out.
There Ain't No Such Thing As A Free Lunch.

Yep, that's it. I did a study of antenna patterns for a simple
vertical dipole over ideal ground at various altitudes:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Despite that official antenna gain of a dipole being 2.15dBi, at
various altitudes, the gain is quite a bit higher. At 5 wavelengths
or more, the maximum gain is about 7dBi.
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/vertical-dipole-5-0-wavelengths.html
However, the beamwidth of the lobe that has 7dBi gain is so narrow as
to be useless. The slightest antenna tilt will put the other end of
the path into lower gain lobe, or into a null.

Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558