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Old July 17th 03, 08:17 AM
Ian White, G3SEK
 
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Dr. Slick wrote:

But an antenna must be performing some sort of transformer action.


Not quite - but there is a word for what it does: it's a transducer.

A transducer is any gadget that converts energy from one form into a
*different* form. Examples include a loudspeaker (electrical energy to
sound/mechanical energy), a microphone (the reverse), a light bulb and a
photocell.

From that point of view, a resistor is a transducer that converts
electrical energy into heat energy... but it also has some useful
electrical properties :-)

An antenna is a transducer that converts electrical energy into E and H
fields, and the reverse.

You'll also notice that all practical transducers convert some of their
input energy into heat energy.

It's a useful word for a useful idea.

(Cecil - can your IEEE Dictionary help us with a formal definition?)


On the other hand, if you insist on using the word "transformer", you'll
keep on believing you can work out new facts about antennas from what
you already know about transformers:
If an antenna is not a transformer of some type, then why is it
affected by it's surroundings so much? They obviously are, just like
the primary's impedance is affected by what the secondary sees in a
transformer.


That's a perfect example of the trap, because in reality it's not "just
like". An antenna also has E-field interactions with its environment
that a transformer doesn't have, so any resemblance will literally be
only half-true.


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