Gene, W4SZ wrote:
"At least two people have explained why that voltage is not one volt per
meter."

Here are Terman`s exact words again:
"The strength of the wave measured in terms of microvolts per meter of
stress in space is also exactly the same voltage that the magnetic flux
of the wave induces in a conductor 1 m long when sweeping across this
conductor with the velocity of light."

I see Gene`s statemennt as a contradiction within itself. Definition of
field strength is the volts it will generate in a wire 1 meter long.
There is no contradiction in Terman`s statement.

Best regards, Richard Harrison, KB5WZI

Richard,

Not only are you misunderstanding Terman, you have twisted my words as well.

I said, "At least two people have explained why that voltage is not one
volt for an incident field strength of one volt per meter."

You removed some of my words and completely changed the meaning.

Once more, Terman is undoubtedly correct with his statement. I agree
completely. However, the configuration described by Terman is NOT the
subject at hand.

73,
Gene
W4SZ


Richard Harrison wrote:
Gene, W4SZ wrote:
"At least two people have explained why that voltage is not one volt per
meter."

Here are Terman`s exact words again:
"The strength of the wave measured in terms of microvolts per meter of
stress in space is also exactly the same voltage that the magnetic flux
of the wave induces in a conductor 1 m long when sweeping across this
conductor with the velocity of light."

I see Gene`s statemennt as a contradiction within itself. Definition of
field strength is the volts it will generate in a wire 1 meter long.
There is no contradiction in Terman`s statement.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:

Gene Fuller wrote:
"There is no problem with Terman`s words, but I believe you are missing
his intention."

I parsed Terman`s words carefully trying to avoid misinterpretation.

There is a RCA FM Coverage Calculator (special slide rule) pictured and
described on the internet. Text accompanies the rule. This text says the
range of the rule is for a radius of urban coverage of 1000 microvolts
per meter and a radius of rural coverage of 50 microvolts per meter.
They obviously anticipate a much higher urban noise level than found in
rural areas.

The rule has distance scales of 4 to 100 miles, and 16 to 143 miles..

The text says: "If you hold up 1 meter of wire at exactly the right
angle, this is exactly how many millionths of a volt are generated
between its ends.


And just how are you going to measure that voltage without getting an
opposite voltage in your voltmeter leads. Or alternatively how can you
present that voltage at the input to a receiver?

You can't. So the above tells us zip about the question Reg asked. Roy
answered the question correctly and you haven't even attempted it. Why
is that?

Andy

Reg, G4FGQ wrote:
"Terman, Kraus, and Balanis and some computer programs are of no help!"

My dictionary defines "field strength" as:
"3. The strength of radio waves at a distance from the transmitting
antenna, usually expressed in microvolts-per-meter. This is not the same
as the strength of a radio signal at the antenna terminals of the
receiver."

The definition looks OK to me. The reason the signal is not the same as
the microvolts-per-meter even when the antenna is a 1-meter length of
wire with just the right slant is because the induced voltage gets
divided between the antenna and its load (the receiver).

Maybe Cecil`s IEEE dictionary has something to say about field strength.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Maybe Cecil`s IEEE dictionary has something to say about field strength.

magnitude of the electric field vector in volts per meter, or
magnitude of the magnetic field vector in amps (or ampere-turns) per meter,
or power flux density P in watts per square meter.
--
73, Cecil http://www.qsl.net/w5dxp

On Tue, 20 Dec 2005 14:40:14 GMT, Andy Cowley
wrote:
The text says: "If you hold up 1 meter of wire at exactly the right
angle, this is exactly how many millionths of a volt are generated
between its ends.
And just how are you going to measure that voltage without getting an
opposite voltage in your voltmeter leads.

Hi Andy,

You make a loop.

73's
Richard Clark, KB7QHC

Andy wrote:
"So the above told us zip about the question Reg asked. Roy answered the
question correctly and you haven`t even attempted it."

I assumed the definition of "field strength" correctly answered Reg`s
question and his descrepancy lay elswhere.

Field strength of an electromagnetic wave is expressed in microvolts per
meter. It is defined as the number of microvolts which would be induced
in a properly placed piece of wire one meter long.

If a field strength of one microvolt per meter does not induce one
microvolt into a piece of wire one meter long, why not? I`ve been
looking for an explanation and found a possible answer in Figure 2-9-1
on page 31 of Kraus` 3rd edition of "Antennas".

The possible explanation is called the "effective height" in meters of
an antenna. It is a "factor", which when multiplied by the microvolts
per meter of the field strength, gives the volts induced in the antenna
at its terminals.

According to Kraus` figure, h is a function of current distribution in
the antenna. The text says that for a dipole 0.1 lambda long, h = 0.5X
the length of the antenna. Reg did not specify a frequency or wavelength
for his antenna, as I recall, and he did specify a ground mounted
vertical whip 1 m long for his receiving antenna.

For a dipole 0.5 lambda long, Kraus gives (h) as 0.64X the length of the
antenna.

For all I know, there is a vertical antenna length in terms of
wavelength for which h=1. If so, the volts between the antenna base and
the ground directly under it would numerically exactly equal the
microvolts per meter of the field strength. All we need to do is pick
the right frequency. The applicable Formula is (1) on page 30.

I suspect that in most cases, h is determined experimentally.

I regret I`ve not had a copy of Kraus nearly as long as I`ve had a copy
of Terman. I`m still using an edition I`ve had for 58 years. It shows
lots of wear and tear.

Best regards, Richard Harrison, KB5WZI

On Tue, 20 Dec 2005 15:33:50 -0600, (Richard
Harrison) wrote:

For a dipole 0.5 lambda long, Kraus gives (h) as 0.64X the length of the
antenna.

Hi Richard,

This is exactly (within one percent) of what the NIST uses for their
standard field measurements (described elsewhere in these threads).

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
You make a loop.
======================================

I normally reply, if I reply at all to your idiotic statements, with
"Phooey".

But on this occasion, to protect innocent, bystanding, novices from
your deliberate, inexcusible, misleading statement, it should be said
that the voltage induced in a circular loop is altogether different
and very much smaller from that induced in a straight wire of the same
length.

You disgust me! A disgrace to amateur radio!

Have a miserable Christmas!
----
Reg, G4FGQ.

Reg, G4FGQ wrote:
"Have a miserable Christmas!"

In the cinema, "The Grinch Who Stole Christmas", the Grinch turned into
a kind, green, Santa Claus. Let`s hope Reg has a change of heart too!

Merry Christmas, Richard Harrison, KB5WZI