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PF1F > ANTENA 04.01.05 23:33l 32 Lines 907 Bytes #999 (0) @ WW
BID : 8F0058PF1F
Read: GUEST DG8DG DL5DKW OK1VKZ
Subj: Re: Antennas and why?
Path: DB0FHN<DB0MRW<DB0FOR<DB0SIF<DB0FHK<DB0FBB<DB0GOS<ON0AR<ON0AR<PI8WFL
Sent: 050104/2115Z @:PI8WFL.#NH1.NLD.EU #:10272 [Enkhuizen] $:8F0058PF1F
From: PF1F@PI8WFL.#NH1.NLD.EU
To : ANTENA@WW
(Dick, VK3ABK)
>> This is the impedance of free space which can be
>> computed knowing the dielectric and magnetic properties, and this comes
>> out
>> to be about 277 Ohm
(Andy, GM7HUD)
> Isn't it 377 Ohms ?
Yes it is, and it is the very reason that mains sockets have holes that
close when it is not in use (except outside England).
This prevents the 0.64 Amperes flowing into free space otherwise.
We can't have all those amps sloshing about the floor!
(... hmm ...)
There is no more reason for the terminal impedance of an antenna to equal
the impedance of free space
than there is for the terminal impedance of a loudspeaker to equal the
acoustic impedance of free air - or even to have some relation to it.
That efficiency is difficult to attain with low radiation resistance, is
quite another matter.
Rudolf, PF1F (PA2RHB)
Heemskerk, JO22im
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