On Tue, 31 Jul 2007 15:45:19 -0400, Michael Coslo
wrote:

I tend to agree with Roy. Omni or not, Every antenna radiates in every
direction. Maybe not as much in one as the other, but radiate they do.

So many folks look at the Take off angle as some sort of blob that
leaps off the antenna at a particular angle, and if it isn't at that
"correct" angle, then heaven help you i you are trying to operate NVIS
or DX or whatever.

Hi Mike,

Another metaphor would be Craps shooting. The distribution of
separate outcomes is each 1 in 36, but there are a preponderance of 7s
over time with very much higher probability. To ignore the
preponderance (this blob) to the observation of single rolls would
have left the design of antennas stuck in the age of Marconi.

That being the case, I questioned if assuming that the angle for best
reception is also the angle for best transmission, especially with what
appears to be a change over time.

Reciprocity is another one of those rules revealed by the
preponderance of outcomes - and so often decried as impossible through
single reports of failure.

However, returning to the original link, and the design behind it, it
is called beam forming as practiced through controlled delays. If the
math reveals that a signal is peaked with one particular setting of a
combination of delays, and if that combination reveals an apparent
source coming in from a particular angle; then we can say that yes,
Virginia, there is a take off angle. We can reasonably expect that
calling back through the same combination of delays through to those
various antennas will result in a more optimum link.

That, or through this design, you can adjust to obtain that optimum
(which will more than likely reveal another take off angle). You will
then be able to ponder why they come in best at one angle while you go
out best at another. Yes, a distinct possibility that becomes more
distinct through this control, and the resolution of take off angles.

Now, as to the matter of this "some sort of blob that leaps off the
antenna." Modeling propagation will reveal if you define a circuit
(the point of origination and the intended audience's location), and
you chip in the general antenna radiation lobe characteristic; then at
significant distances a matter of one degree can be resolved. For
sharply lobed antennas (and this 6 bay is quickly approaching that),
the roll-off response and a one degree shift can plunge the listener
into deafness. Of course, the vagaries of propagation can easily
upset the apple cart - but again, this sharply reveals how "some sort
of blob" has become distinctly important compared to the gross
distribution of possibilities.

73's
Richard Clark, KB7QHC