A vertical antenna can be either a good or a bad radiator, the
concept is quite relative, it depends....
First of all, the common assumption that a vertical antenna is a
low angle radiator is often unrealized because of refractions
and reflections of ground.
A vertical antenna can be a low angle radiator but often it is
not true.
The image antenna of a vertical, is theorically in phase with the
real antenna. The consequence is that at 0 degrees of radiation
angle, there should be a 3DB gain (maximum).
A zero degrees radiation only says that verticals are potentially
good antennas to produce more ground ground wave than horizontal
ones. More gain at proper angles is another story, at least for DX
and sky wave propagation.
Now, in the real life I mean, a vertical antenna is effectively a
low angle radiator only when the pseudo Brewster angle is quite low,
some unity, but this happens only over sea water and other extremely
good grounds.
Below the brewster angle, the image antenna phase reverses, and
there is rather a cancellation than a sum in the radiated energy !
Moreover, the "very good ground" to be effective, must extend for
a large area (just below the antenna it's not enough) and this makes
vertical antennas performance mostly depending on enviromental
situation ( the location ).
Luckily, HF propagation in the low bands doesn't require so low
angles (the 1 or 2 deg of 10 meters are totally useless), and even
an imperfect ground (i.e. producing a pseudo brewster of some 10deg)
doesn't prohibit the vertical from radiating effectively for DX
and sky wave traffic (above Brewster)
However, an horizontal antenna at a reasonable height from ground,
can offer as much as 6DB of gain for some angles, and with a much
lower dependency by ground characteristics.
Here it cames the reality that for the typical wave angles of
160 80 and 40 meters, an horizontal antenna placed at reasonable
height from ground can outperform a vertical array in gain (the
directivity and immunity to high angle signals of a phased array is
a different story) and, in the near of slooping grounds or other
discontinuities could "beat" a vertical antenna up to some 12 DB.
Personally I noticed 10DB gain on 80meters when replaced a 4 half
wave verticals (dipoles) phased array, in favour of a 2 phased
horizontal dipoles at 150 feet from ground.
73, Mauri I4JMY (one of IR4T)
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