IF this data is the same as N6BV published in the ARRL
Antenna Book, it ASSUMES antenna heights of 100 ft
for 80 through 17 meters and 60 ft for 15, 12, and 10M
at BOTH ends of the path.
Naturally all of the favored angles correspond to the wave angles
covered by those heights and NO propagation at the angles
that correspond to the NULLS corresponding to those heights
(20 degrees on 20M for example). Also note that 15M
supposedly supports higher waveangles than 17M. This is
a direct result of using 60 ft high reference antennas on 15M
vs 100 ft high on 17M. The data tells us more about the
restrictions of the reference antennas than it does about
the upper limits of the ionosphere.
He later revised his studies assuming isotropic sources
at both ends which showed more instances of high angle
paths but still does not specifically address the case of
a LOW transmitting antenna at the DX end such as is
used by the majority of DX stations, especially the ones
that run around answering (our) CQ's.
To the best of my knowledge there is NO published data which
assumes LOW ANTENNAS at the DX end, i.e. your typical
DX station antenna system. Any volunteers to explore this study?
It seems intuitively obvious that if a DX station is using a low
antenna which concentrates it's radiation in the higher angles,
and the ionosphere supports higher angles, then the greatest
received energy would frequently correspond to those higher
angles.
Let us not forget the effects of the D and E Layers when the
sun is up. The lower the takeoff angle, the more time the
signal spends in the D layer. If the additional D Layer
absorption exceeds the reflection loss of an additional hop,
then the higher angle signal will be stronger which supports
the (considerable) anecdotal reports of higher angles
being stronger during midday, especially for (DX) stations
with low transmitting antennas.
E Layer 'bending' may also contribute to this phenomenen.
Even though the E-layer MUF is usually below 14 MHz,
refraction when passing through the E-layer can take a
high angle signal and 'bend' it to a lower angle that proceeds
onward to the F layers.
Since these D and E layer effects are sun related, they
may be more prevelent the closer one is to the equator.
I recall N4AR telling me how he would sometimes hear an echo
on European signals when using his 4 high 10M stack which
had a primary lobe at 6 degrees. The echo went away, and signals
were louder, on a separate single 10M beam at 40+ ft. with it's
primary lobe centered around 12 degrees.
Could it be that the European signals had more energy in the
higher angle 4 or 5 hop mode than in the 3 hop mode but N4AR's
low angle antenna system was pulling in the weaker low angle
mode and suppressing the stronger high angle mode, creating
an echo?
As KL7RA once said (or was it KL7Y?)
"You can never have enough antennas"
to cover all the propagation variations.
He was amazed at how a low 10M beam
was often best to the USA and was joked
that if he put it any lower, he'd have to
worry about someone poking out an eye.
Yet the quest to find the ONE ideal height
that will be optimum for ALL times never
seems to fade away...
I fully appreciate the times when a very high
antenna is the only antenna that will pull a
distant (usually Asian) DX station through,
typically on a closing or marginal MUF band,
but I don't accept that it will ALWAYS be the
best antenna for all paths at all times of the day.
I don't understand the reluctance of so many
one tower owners to install a lower antenna
(even a multiband dipole such as the D3)
on a tower leg to fill in the unavoidable NULLS
of higher antenna(s).
Tom N4KG
On Thu, 10 Jan 2002 "Jim Reid" <jimr.reid@verizon.net> writes:
>
> An excellent "book" on this subject was published
> in 1993 by LTA and the Radio Bookstore. Book is by R. Dean
> Straw, N6BV, titled "All the Right Angles".
>
> The book is full of detailed data, charts, computer
> print outs, etc. Also includes a diskette with both
> added data and antanna modeling stuff. If you can
> find a copy, you will learn all about antenna performance
> at many DX locations about the world, specific station
> antenna set ups, etc., etc. I have a copy, including
> the diskette, not sure of the value, but for the "right"
> offer I would sell, hi. 81/2 by 11 format in soft-cover
> binder.
>
> Copies "might" still be available from either LTA,
> New Bedford, PA., phone 216-565-9950, or
> Radio Bookstore, Rindge, NH., phone 800-457-7373.
>
> Those are the indicated addresses and phone numbers
> shown on the covers of my copy; don't know if these
> folks are still at those places.
>
> Data is given for just about everywhere on the US mainland
> to various other spots about the world as well as data
> from both Western and Eastern Europe, and Japan to
> the world. A very comprhensive work on antenna sorts,
> heights and geography to and from just about anywhere
> to anywhere!
>
> 73, Jim KH7M
>
>
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