On Sun, 06 Mar 2005 14:11:30 GMT, "
wrote:

Now I understand where you are coming from !.
I've given a lot of info out about the antenna
and its attributes, many of which are unique.

Hi Art,

To that, all that info rarely comes in one post or even within the
scope of one thread.

Also why I am following this path
I do not consider these posts mention of the attributes such as
feed point height or details regarding F/B as meaningless
and certainly not points about which to argue.

No, no argument, simply put, it is needed information to base any
discussion upon. When it is lacking (and when only you can supply
it), then there is no point for discussion. You might want to
consider this in light of your next quoted line:
I did ask on another posting if there was anything written on a particular
subject regarding a particular feature but there was no response so there is
not a lot of interest in some aspects

but at this point I am not ready to publish all details which I am sure that
you
understand
I don't, but that is not the point. If you don't have all the
details, that is fine as long as you say so. This allows
correspondents to add their own insights to help you. If you do have
all the details, and say nothing, there is not much to talk about and
we have to wonder why you are posting at all.

73's
Richard Clark, KB7QHC

Needing a break from the exceedingly excruciating task of preparing income
taxes, I took a break to investigate what EZNEC/4 has to say.

To facilitate checking and to use an antenna with more vertical pattern than
that of a dipole, I used as an antenna the 14.2 MHz five-element Yagi
provided with EZNEC. I looked at the first and second peak and the first
null (above the horizon) for three types of ground. I also used three
heights.

---We all know the uncertainties with estimates of the characteristics of
ground, so let us not replay the issue.---

The conductivity in SI units and the relative dielectric constant
immediately follow the height in meters. Angles are in degrees above
horizon.

H = 22 meters
0.005 13
peak 12.5; null 28.3; second peak 41.6
0.01 14
peak 12.6; null 28.3; second peak 41.6
0.002 10
peak 12.5; null 28.4; second peak 41.6
Use of equation:
N = 1: 13.9; N = 2: 28.7; N= 3: 46.0

H = 33 meters
0.005 13
peak 8.7; null 18.5; second peak 27.8
0.01 14
peak 8.6; null 18.5; second peak 27.6
0.002 10
peak 8.6; null 18.6; second peak 27.7
Use of equation:
N=1: 9.2; N = 2: 18.7; N = 3: 28.7

H = 44 meters
0.005 13
peak 6.6; null 13.8; second peak 20.7
0.01 14
peak 6.7; null 13.8; second peak 20.7
0.002 10
peak 6.6; null 13.8; second peak 20.7
Use of equation:
N = 1: 6.9; N = 2: 13.9; N= 3: 21.1

-------
One could conclude that the farther above ground one is and the smaller the
relevant angles are, the better the fit with the equation. Think about why
the first peak above real ground occurs at a smaller angle than what would
be the case with a perfect ground.

As several have commented, what counts is to have gain at the angles to be
used for propagation. The equation provides some useful information but it
needs to be understood. No substitute exists for having a horizontally
polarized antenna at heights that are appropriate for the task.

One extensive project that I worked on involved distances less than one hop.
A significant issue was the desire to minimize gain at low angles where
interference resided. Among other things, it was important to suppress
vertical radiation as much as possible by choking the transmission lines and
by having the wires be close to horizontal.

A point in engineering is to know/learn what the desired end results are and
then to use tools that are to-hand to approximate the desired end results.
In the case of HF systems, as many have observed, a statistical knowledge of
propagation plays a large role.

Back to taxes. Any man-made system of such complexity is inherently
inequitable.

73 Mac N8TT

P.S. For receiving purposes, combining a high antenna with an identical
antenna about 0.5 WL lower can almost cancel the second lobe and thus
attenuate much of the first hop (strong) QRM. Such a scheme does little for
transmitting effectiveness. Compare the placement of the null using H= 33
with the second peak using H = 44.

--
J. Mc Laughlin; Michigan U.S.A.
Home:

This is not my thread which is about TOA. I did add a posting remarking
about
TOA and you took on yourself to say it was meaningless. In your normal
fashion you took on laying a foundation for augument rather than
correcting the term to make it meaningfull.If you contribute to the thread
by
giving the correct term for the angle of take off, then many would be
interested.
On the other hand I did initiate a post regarding max gain and F/b being on
the
same frequency and the basis or logic that I drew upon to make that
statement.
You often take the aproach that all is known ( or you know it all) and if
there
is no written evidence pertaining to it then it is false and an augument
then follows.
Now that is you chance for you to wax and wane as to why that logic is
faulty
which by being the author I would be duty bound to respond and defend my
statement .
All I do ask for is you keep your responses to the subject at hand and not
to invoke
Shakespeare or the Doyle Carte company renderance of the Pirates of Penzance
as proof
knoiweledge of your critique.



"Richard Clark" wrote in message
...
On Sun, 06 Mar 2005 14:11:30 GMT, "
wrote:

Now I understand where you are coming from !.
I've given a lot of info out about the antenna
and its attributes, many of which are unique.

Hi Art,

To that, all that info rarely comes in one post or even within the
scope of one thread.

Also why I am following this path
I do not consider these posts mention of the attributes such as
feed point height or details regarding F/B as meaningless
and certainly not points about which to argue.

No, no argument, simply put, it is needed information to base any
discussion upon. When it is lacking (and when only you can supply
it), then there is no point for discussion. You might want to
consider this in light of your next quoted line:
I did ask on another posting if there was anything written on a particular
subject regarding a particular feature but there was no response so there
is
not a lot of interest in some aspects

but at this point I am not ready to publish all details which I am sure
that
you
understand
I don't, but that is not the point. If you don't have all the
details, that is fine as long as you say so. This allows
correspondents to add their own insights to help you. If you do have
all the details, and say nothing, there is not much to talk about and
we have to wonder why you are posting at all.

73's
Richard Clark, KB7QHC

If one writes the equation, for elevation angles of nulls and maximums, in
terms of free-space wavelength instead of frequency, an even more simple
equation is obtained :

Beta = ArcSin( N * Lambda / 4 / Height ) degrees.

Where Lambda is free-space wavelength
and Height is height above ground.

When N is odd, Beta corresponds to a maximum in the pattern.
When N is even, Beta correspnds to a null in the pattern.
----
Reg, G4FGQ

Dear Reg:
Quite. I have found it more useful to use frequency.
73 Mac N8TT

P.S. The peaks and nulls suggested by the equation agree quite well when
compared to those resulting from using a "perfect" ground with EZNEC/4 as
long as the angles are less than about 30 degrees. In FS, the Yagi is down
1 db at 21.5 degrees and down 2 db at just under 30 degrees.

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Reg Edwards" wrote in message
...
If one writes the equation, for elevation angles of nulls and maximums, in
terms of free-space wavelength instead of frequency, an even more simple
equation is obtained :

Beta = ArcSin( N * Lambda / 4 / Height ) degrees.

Where Lambda is free-space wavelength
and Height is height above ground.

When N is odd, Beta corresponds to a maximum in the pattern.
When N is even, Beta correspnds to a null in the pattern.
----
Reg, G4FGQ

Art Unwin wrote:
Gon`t professionals use the term (take off angle)?"

The FCC publishes vertical radiation patterns for grounded vertical
radiators of several heights between 0.25 and 0.625 wavelengths. These
and selected other curves are made a part of the rules. These curves
must be used to compute the probable skywave intensity in another
station`s service area whenever it appears a questionable interference
may occur. Skywave computations are approximate but give results which
are reliable over a fairly predictable percentage of the time.

The term used by the FCC is "elevation angle" or departure angle. The
FCC governs radiation.

Determining radiation from broadcast stations is a job for professionals
who use the term "elevation angle".

Best regards, Richard Harrison, KB5WZI