Peter O. Brackett wrote:
Why do you think *uniform* is any better than any other distribution of
Rrad?

Here's a quote from _Antennas_, by Kraus & Marhefka: "... the radiation
resistance may be thought of as a virtual resistance that does not exist
physically but is a quantity coupling the antenna to distant regions of
space via a virtual transmission line."
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil, W5DXP wrote:
"Here`s a quote from _Antennas_by Kraus&Marthelka: "... the radiation
resistance may be thought of as a virtual resistance that does not exist
physically but is a quantity coupling the antenna to distant regions of
space via a virtual transmission line."

A problem comparing radiation to a transmission line is that everytime
line length increases a fixed amount, so does the loss. The loss is so
many db per mile. After a radio wave travels a million miles, the next
million miles only produces an additional 6 db loss. Thus, we are
looking at radio pictures from Mars. We couldn`t get them by the lowest
loss coax from Mars without distributed repeaters.

I can`t find my 1955 edition of Terman but as I recall he says that
radiation resistance is equal to the resistor, which if placed in series
with the antenna, would consume the same power that the antenna does.
Radiation resistance is a useful fiction. Radiation resistance is
usually the resistance at an antenna`s maximum current point. Fictional
or not, it can be measured with an impedance bridge.

My 1937 edition of Terman says:
"---fields produced by the antenna currents induce back voltages that
are equivalent to an impedance against which the applied voltage can be
considered as acting."

Terman also says: "In addition to the radiated energy, energy is also
lost in the antenna system as a result of wire and ground resistance,
corona, eddy currents induced in neighboring masts, guy wires and other
conductors, and dielectric losses arising from such imperfect
dielectrics as trees and insulators, located in the field of the
antenna. These losses can be represented in the same way as the radiated
energy, i.e., by a resistance which inserted in series with the antenna
will consume the same amount of power as that actually dissipated in
these various ways. The total antenna resistance is the sum, Rr + Rl, of
the radiation resistance Rr and the loss resistance Rl, and determines
the amount of energy that must be supplied to the antenna to produce a
given current.

The efficiency of the antenna as a radiator is the ratio Rr / (Rr + Rl)
of radiation to total resistance. This represents the fraction of the
total energy supplied to the antenna which is converted into radio
waves."

Terman also says:
"The radiated field (epsilon) varies directly as the current I, the
frequency f, the doublet length (delta)l, and the cosine of the angle of
elevation, and is inversely proportional to the distance d."

The strength of the radiation from an antenna at a point P is the sum of
the strengths of the fields of its elemental pieces carrying a current
I.

Current is not uniform throughout the usual antenna and neither is the
antenna`s impedance. The current is zero at the open ends of an antenna,
near zero at exact multiples of a half wave length distant from the open
end, while the current is maximum at points that are odd quarter wave
lengths distant from the open ends.

Best regards, Richard Harrison, KB5WZI

Cec and others, what's the point in dragging in opinions of people nobody
has ever head of and whose publications are highly unlikely ever to become
available before all interest in the subject has faded from everybody's
imagination.

If anything needs to be said, would it not be better to say it just on one's
own authority and be done with it. Otherwise it falls into the category of
"name dropping".
---
Reg

On Tue, 6 Jan 2004 03:58:18 +0000 (UTC), "Reg Edwards"
wrote:

I never support my stuff by citing

On Mon, 5 Jan 2004 04:41:03 +0000 (UTC), "Reg Edwards"
wrote:

to keep Roy happy

On Tue, 6 Jan 2004 03:58:18 +0000 (UTC), "Reg Edwards"
wrote:

But I daresay Heaviside preceded me.

On Tue, 6 Jan 2004 18:28:33 +0000 (UTC), "Reg Edwards"
wrote:

Clement Attley who had usurped Churchill

On Tue, 6 Jan 2004 18:28:33 +0000 (UTC), "Reg Edwards"
wrote:

I once met Josephson

On Tue, 6 Jan 2004 18:28:33 +0000 (UTC), "Reg Edwards"
wrote:

Captain Evans

On Wed, 7 Jan 2004 16:18:52 +0000 (UTC), "Reg Edwards"
wrote:

If anything needs to be said, would it not be better to say it just on one's
own authority and be done with it. Otherwise it falls into the category of
"name dropping".
---
Reg

I don't agree (and apparently neither do you).
If names were snowflakes, this would be an avalanche. :-)

73's
Richard Clark, KB7QHC

Reg Edwards wrote:
Cec and others, what's the point in dragging in opinions of people nobody
has ever head of and whose publications are highly unlikely ever to become
available before all interest in the subject has faded from everybody's
imagination.

Reg, everyone except you has heard of John D. Kraus, W8JK. My personal
library would be extremely incomplete without his book(s).

If anything needs to be said, would it not be better to say it just on one's
own authority and be done with it. Otherwise it falls into the category of
"name dropping".

In physics and engineering circles, it's called providing a reference.
Without a reference, it is just a personal opinion, unless one can
prove otherwise. With a proper reference, it is generally accepted as
fact, unless one can prove otherwise. Check out all the references
at the end of any technical article.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Reg Edwards wrote:
Cec and others, what's the point in dragging in opinions of people
nobody
has ever head of and whose publications are highly unlikely ever to
become
available before all interest in the subject has faded from everybody's
imagination.

Reg, everyone except you has heard of John D. Kraus, W8JK. My personal
library would be extremely incomplete without his book(s).

If anything needs to be said, would it not be better to say it just on
one's
own authority and be done with it. Otherwise it falls into the category
of
"name dropping".

In physics and engineering circles, it's called providing a reference.
Without a reference, it is just a personal opinion, unless one can
prove otherwise. With a proper reference, it is generally accepted as
fact, unless one can prove otherwise. Check out all the references
at the end of any technical article.
--
73, Cecil http://www.qsl.net/w5dxp

=============================

Cec,

You know very well I have heard of Kraus. But only by reputation on these
walls. He must be a professional who by chance happened or happens to have a
call sign as so many American engineers do. As I am myself it so happens.
But that's about all of it.


The reputations of American amateurs and professionals appear to have become
mixed. In my opinion to the benefit of neither.


References are of no use unless they are accessible. It is of no use
recomending references to people who are without ready access to them.
People with ready access wouldn't be asking questions in the first place.


I have only two reference books of consequence. One author's name is
Terman. Believe me I have come to the conlusion that 99 percent people who
worship and specify Terman have never actually used him except merely for
quotations which they don't understand anyway. He need a lot of checking
before placing one's life in his hands. I say this as one who HAS used him
on occasions over the years but only as a very comprehensive and valuable
source of memory refreshment. But I have NEVER dropped his name to
strengthen my own statements. And nobody else's name either to my
recollection.


Whenever I see references to authors (most of which I've never heard of
except on these walls) I am inclined to the opinion the person making the
reference lacks self confidence in what he's waffling about.


But of course, when a reference is made for the purposes of further reading
should the source be readily available, then that's fine. But in such cases
I know full well the chances of getting my hands on a particular reference
within 6 months are remote. And should I ever get it it is unlikely to tell
me what I want to know anyway. Been there - done that too many times in
the past to expect otherwise. So as far as I'm concerned the matter is best
dropped. To minimise the losses just change the subject! To proceed is
never worth the trouble.


My other reference is Everitt. Far more reliable. I've never found a single
error in 55 years. I use him only every few years because I know him mostly
by heart anyway. You may think my knowledge base is exeedingly small. It
is!


Perhaps I could have explained the foregoing in better terms. But most of
you understand exactly what I'm saying. English and American English become
closer every day. Our politicians tell exactly the same lies.
----
Reg, G4FGQ

On Sat, 10 Jan 2004 01:35:32 +0000 (UTC), "Reg Edwards"
wrote:

But I have NEVER dropped his name to
strengthen my own statements. And nobody else's name either to my
recollection.

Short recollection. That is why folks supply citations. [merely
stating the bleeding obvious]

73's
Richard Clark, KB7QHC

Reg Edwards wrote:
References are of no use unless they are accessible.

Reg, if I need to look at a reference, I just drive 40 miles
over to the Texas A&M library. If I really like it, I buy one.
I bought 4 reference books last year.
--
73, Cecil http://www.qsl.net/w5dxp



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Reg Edwards wrote:

SNIP

Citing references is standard in the business where I last did technical
work.
Most good libraries have a reference section. Most technical
colleges/universities also have excellent resource sections. Anyway ...

SNIP

Our politicians tell exactly the same lies.
----
Reg, G4FGQ



Here in central NH this morning it is getting cool. Real cool. Air
temperature is -8F and still going down at 1200Z. Why, it's so cold that
the local weatherman chided that ... are you ready for this??

"It's so cold the politicians are keeping their hands in their own pockets."

Love it!! DD, W1MCE

Reg Edwards wrote:
Cec and others, what's the point in dragging in opinions of people
nobody has ever head of and whose publications are highly unlikely ever
to become available before all interest in the subject has faded from
everybody's imagination.

If anything needs to be said, would it not be better to say it just on
one's own authority and be done with it.

We already noticed. But if anyone else tried that, guess who'd call it
"plagiarism"?

Otherwise it falls into the category of
"name dropping".

Cecil has it right: it's called "a reference".


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek