On Wed, 5 Apr 2006 19:51:45 -0500, "Richard Fry"
wrote:
"Richard Clark"wrote
Sounds like you have a problem following context.
....
If you can find ANYTHING in my posts on this subject to support your
statements, please quote them to the NG.
What a tedious imposition to have to repeat correspondence, but if
that is your price, then only one example in full:
On Tue, 4 Apr 2006 12:11:20 -0500, "Richard Fry"
wrote:
The effective electrical length of a MW monople radiator determines its
resonant frequencies, and that must include the velocity of propagation
along the structure -- which is a function of the height AND width of the
radiator (mainly), and the operating frequency.
KYMN 118.60° tall 92.3 meters tall 1080 kHz
http://www.fcc.gov/mb/audio/amq.html
The FCC recitation of these facts is one such MW monopole radiator.
We proceed to YOUR reference:
"Antenna Engineering Handbook," 2nd edition (pub. 1984), by Johnson and
Jasik
specifically to YOUR point
a function of the height AND width
which is manifest in figure 4-4.
If you cannot resolve that graph, and for others reading, it shows a
family of curves constructed on the basis of A/D which is elsewhere
described as Length over Diameter.
For a radiator of 118.60° tall the only curve passing through zero
reactance is assigned an A/D of 20. A is already known and is
118.60°. It then follows to satisfy the A/D of 20 drives the value of
D to be 5.93° which for a wavelength of 277.8 meters works out to be a
diameter of 4.58 meters (corrected from my computational error
earlier).
In EZNEC the thin wire model reveals a source Z of:
Impedance = 97.63 + J 371.5 ohms
which confirms against figure 4-4's example for an A/D=1000
I don't know the validity of forcing the radiator to the 4.58 meter
specification, but EZNEC clearly shows that move drives out reactance
with a source Z of:
Impedance = 133.8 + J 78.91 ohms
This, too, conforms to figures 4-3 and 4-4 to within acceptable limits
of error. If that offends your sense of accuracy, we can take it
outside.
I see no need to proceed further along lines that clearly follow the
precepts offered by J&J.
Now, returning to the diameter that has been proven to be necessary to
resonate this instance which you dismiss as "ridiculous examples," my
comment about seeing very few towers that exhibit this magnitude of
diameter (the size of my living room) still stands as unimpeached.
Going further into your cavalier dismissal of "ridiculous examples" we
find that there are a forest of very short antennas in service. My
link provides so many in one frequency assignment that the force of
numbers cannot be denied so simply, and certainly when lacking
technical rebuttal. Those offered such as:
WXNH 56.30° tall 540 kHz
when run through the same exercise above (YOUR reference, YOUR claims)
reveals a necessary A/D of LESS THAN 5. The simple math resounds with
the implications of necessary diameter to resonate this through (YOUR
claims YOUR quotes of):
"The effective electrical length of a MW monopole radiator
determines its resonant frequencies, and that must include the velocity of
propagation along the structure -- which is a function of the height AND
width of the radiator (mainly), and the operating frequency."
For a wavelength of 555.6 meters, that A/D resolves D to a value of
111 meters (and this arbitrary selection of A/D=5 is NOT the necessary
value it is less) or the 364 feet. I see no reason to impeach J&J by
attempting this with EZNEC for a result that is so obviously absurd in
the real world to achieve.
This absurdity reveals that it takes much more than these intellectual
shenanigans of height AND (YOUR emphasis) width to resonate a short
antenna. Please note THIS context which has been part and parcel to
these threads for more than 1000 pieces of correspondence.
Hence, the suite of recited example antennas clearly exhibit an
expressed height, in degrees, that are strictly an expression of their
physical height in terms of wavelength, and have nothing to do with
their being resonant OR non-resonant. It is equally clear that in
their service, there have been means made to resonate them, and that
does not impact their height description either.
73's
Richard Clark, KB7QHC
p.s.
No, from your posts IMO it is YOU who has a problem with your reading
comprehension, and/or possibly your professional integrity.
This is an amateur forum, and I don't trade on my professional
credentials to retail them as proof. Reading comprehension is best
left to the rest to evaluate; and as many express confusion, or
difficulty with my writing, none have challenged my data. I can live
with their confusion, and justify that with a quote from Dr. Samuel
Johnson, courtesy of his biographer James Boswell:
Johnson having argued for some time with a pertinacious gentleman;
his opponent, who had talked in a very puzzling manner, happened
to say,
"I don't understand you, Sir"
upon which Johnson observed,
"Sir, I have found you an argument;
but I am not obliged to find you an understanding."