"Szczepan Białek" wrote in message
...
"Peter" wrote
. au...
In the electric power industry there is increasing public concern
regarding fields around power lines. The general public often refers to
these fields as electromagnetic radiation, which it is not.
Yes. Radiation is proportional to f^4. So at 50Hz practically no
radiation.
We generally are concerned with magnetic fields and less often with the
electric charge fields. The two are treated as separate issues.
The two were seperate in ancient ages and now in the textbooks. It is the
necessary simplification.
But the adults have the two ways:
1. The way (EM theory) by Biot-Savart and Maxwell where the current create
the magnetic whirl,
2. The way by Ampere and many others where the moving charge create also
electric field. Here the magnetism is an illusion.
I believe the same is true of antennas, that is the electric and magnetic
fields are separate when you are close in to the antenna in terms of
wave-length.
Question:
If this assumption is correct at what point or distance do the two
relatively independent fields become the one all important
electromagnetic wave?
You have the answers for the way 1.
For the way 2 we have only the one electric wave. But would be easy to you
to check which way is right.
In the way 1 EM waves are radiated by the AC (current create magnetic
whirl and this create electric whirl and so on). Radiate this part of
antenna where the current is max.
In the way 2 the electric waves are radiated by the two ends of Hertz
dipole. So the dipole radiate the two coupled electric waves. The
receiving antena should detect the doubled frequency (on monopoles no such
effect). You must distinguish it from the harmonics.
S*
Peter VK6YSF
http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm
Thanks to all for the response and relatively detailed explanations that has
given me something to ponder.
Regards Peter YSF
--
Peter VK6YSF
http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm