The nature of Free Space (Once called, "The Lumeniferous Aether")
 

"Wayne" wrote in message
...

Well, I don't know what you are calling "retarded potential".

It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.

It is termed, "retarded" because the radiation originated at some time in
the past.

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

"gareth" wrote in message ...

"Wayne" wrote in message
...

Well, I don't know what you are calling "retarded potential".

It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.

It is termed, "retarded" because the radiation originated at some time in
the past.

OK now I know. I hadn't heard the term before.

But, how about my question?

" if the radiated power is equal for two different antennas, why
would the field strength be different, except as related to pattern
differences?"

The radiated power just is spread out differently.

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time in
the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would the
field strength be different, except as related to pattern differences?"
The radiated power just is spread out differently.

Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..

The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.

Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.

HTH

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

"gareth" wrote in message ...

"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time in
the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would
the field strength be different, except as related to pattern
differences?"
The radiated power just is spread out differently.

Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic
Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..

The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.

Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.

But wasn't it implicit in your original statement that the power was equal
in both the 1/4 wave and the shorter antenna?

So for your assertion, we don't need to know the current.

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

"Wayne" wrote in message
...
"gareth" wrote in message ...
"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time
in the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would
the field strength be different, except as related to pattern
differences?"
The radiated power just is spread out differently.
Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic
Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..
The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.
Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.
But wasn't it implicit in your original statement that the power was equal
in both the 1/4 wave and the shorter antenna?

No, for I was referring to the power arriving at some point in the far field

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

On 9/11/2015 1:10 PM, gareth wrote:
"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time in
the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would the
field strength be different, except as related to pattern differences?"
The radiated power just is spread out differently.

Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..

The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.

Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.

There is no contradiction there. Current is not power. Power is
voltage times current. Since the impedance of a short antenna is not
the same as the impedance of a larger antenna, it makes perfect sense
that the current for a given power level will not be the same.

--

Rick

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

gareth wrote:
"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time in
the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would the
field strength be different, except as related to pattern differences?"
The radiated power just is spread out differently.

Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..

The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.

Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.

HTH

Congratulations, you have just confirmed Ohm's law.


--
Jim Pennino

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

wrote:
gareth wrote:
"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time in
the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would the
field strength be different, except as related to pattern differences?"
The radiated power just is spread out differently.

Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..

The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.

Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.

HTH

Congratulations, you have just confirmed Ohm's law.


Does he get a certificate or something to honour this milestone in radio
science?

--
STC // M0TEY // twitter.com/ukradioamateur

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

"rickman" wrote in message
...

There is no contradiction there. Current is not power. Power is voltage
times current. Since the impedance of a short antenna is not the same as
the impedance of a larger antenna, it makes perfect sense that the current
for a given power level will not be the same.

Feed 1kW into your 472kHz antenna and get only 1W erp, most of
the high current driving the ohmic resistance and not the radiation
resistance

The nature of Free Space (Once called, "The Lumeniferous Aether")
 

On 9/11/2015 1:48 PM, gareth wrote:
"rickman" wrote in message
...

There is no contradiction there. Current is not power. Power is voltage
times current. Since the impedance of a short antenna is not the same as
the impedance of a larger antenna, it makes perfect sense that the current
for a given power level will not be the same.

Feed 1kW into your 472kHz antenna and get only 1W erp, most of
the high current driving the ohmic resistance and not the radiation
resistance

You have had this discussion with many others here before. What is your
point? Every antenna design has different losses depending on all the
details of construction. So what?

--

Rick