Vertical Radiation Pattern?
 

This may be a little off topic, but here goes anyway.

I have read somewhere that vertical antennas radiate almost nothing
below the lowest elevation of the antenna.

So, I was wondering if a wireless router also radiates almost nothing
below the router. (The antenna of a wireless router is usually
pointing up.) These devices usually operate at 2.45 GHz.

I know that routers usually have other means of security, but I was
wondering if I could also locate the router such that the radiation
was limited or non-existent in one direction.

Thanks, jimbo

This may be a little off topic, but here goes anyway.

I have read somewhere that vertical antennas radiate almost nothing
below the lowest elevation of the antenna.

Well, a half-wave vertical dipole in free space radiates a pattern
aimed towards the horizon. There's significant radiation both above
and below the horizon. There are deep nulls directly above and below
the antenna, but the null isn't terribly deep once you get more than,
say, 20 degrees on one side of the axis of the antenna.

I know that routers usually have other means of security, but I was
wondering if I could also locate the router such that the radiation
was limited or non-existent in one direction.

I wouldn't count on this at all. Although the pattern will be weaker
in the axis of the antenna, this sort of antenna system is not in free
space. There are all sorts of reflections from metal objects in the
building, and these will tend to fill in the nulls to some extent.

The nulling is sufficient to help reduce interference (to some extent)
between access points located right above one another on different
floors of a building, but it's not completely effective even at that,
and should not be counted on for security or privacy.

--
Dave Platt AE6EO
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