Amen.
Let us use TOA for the elevation angle where an antenna's pattern is
strongest and ATOA for the actual elevation angle used over a long HF path.

At least from 7 MHz to 21 MHz, when DX ionosphere propagation is likely
the ATOA is between about 12 degrees and about 2 degrees. When comparing
antennas to be used for HF DX contacts, it is appropriate to note the gain
at 3, 6, and 9 degrees as being the numbers to compare. The actual TOA (as
defined above) is only interesting.

That said, it is possible to have a single horizontally polarized
antenna that is so high that it suffers in comparison to a lower antenna for
ATOAs of about 10 degrees (by more than the one db that is being talked
about). For one horizontally polarized antenna to be used for DX contacts
the desired heights are two to three wavelengths above earth.

If one can use a plurality of horizontally polarized antennas,
interesting results are possible. For instance: on receive, combining a
lower second antenna with a tall first antenna can effect the approximate
cancellation of the second lobe. The second lobe has a high TOA and can
contribute significantly to the noise and interference received from
relatively short distances. Nulling the second lobe can significantly
increase the received SNR.
For closer spacing of multiple antennas, one can effect more gain than
that of one antenna - with trade-offs.

I emphasize what has been said by Roy and others: TOA (as defined
above) is interesting, but it is not the most important number for DX
contacts.

73 Mac N8TT


--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Roy Lewallen" wrote in message
...
I say ignore the TOA. (For those unfamiliar with the term, it's the
"takeoff angle", which usually means the elevation angle at which the
antenna pattern is strongest.)

What counts is the gain at the elevation angle at which you want to
communicate. This, in turn, depends on the distance and the propagation
conditions. If you need a strong signal at an elevation angle of 15
degrees, it doesn't matter whether the TOA is 10 degrees, 15, or 20 or
zero. All that counts is the gain at 15 degrees. And an antenna with TOA
of 15 degrees doesn't necessarily have the most gain at 15 degrees of
any antenna.

Consider the following three 40 meter antennas: A vertical antenna with
about 8 radials (18 ohm ground system resistance), a dipole at 30 feet,
and a dipole at 40 feet, all over average ground.

Antenna TOA deg Gain at 26 deg. Gain at 15 deg.

Vert 26 -1.76 dBi -2.72 dBi
Dipole @ 30' 90 (straight up) 2.58 dBi -1.28 dBi
Dipole @ 40' 51 3.9 dBi 0.32 dBi

-- Which one has the lowest takeoff angle?
-- Which one is the best for communicating at 26 deg. elevation angle?
-- Which one is the best for communciating at 15 deg. elevation angle?

What does the takeoff angle have to do with which antenna is best?

Roy Lewallen, W7EL