Does anyone understand antenna db gain?

rwbradley wrote:

n7bsn wrote:
Antenna gain is also directional, even an "omni" antenna is "directional". That it concentrates it's "listening" to a plane horizontal to the antenna. If the desired direction is above (or below) that plane, the antenna doesn't yield the published gain.

Not to correct you, but for the benefit of the OP, think of the signal from an Omni directional antenna like the Wilson ones you referenced as somewhat donut shaped

To be more specifc, N7BSN is correct when talking about vertical beamwidth, and the more published GAIN, the narrower the VERTICAL beamwidth. Thats where the gain comes from.

These days with tens of thousands of cell sites sitting at ~100' it may not be a big deal. But in the olden' days when cell sites were placed on 2-3000' towers or mtn top sites, it was often a problem to have high gain, narrow vertical beamwidth antennas whose pattern totally missed the cell site, even though you could see it. Too narrow.