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VK3ABK > ANTENA 02.01.05 06:20l 43 Lines 1215 Bytes #999 (0) @ WW
BID : 34601_VK3KAY
Read: DL5DKW OK1VKZ GUEST
Subj: Re Antennas and Why? (cor)
Path: DB0FHN<DB0FOR<DB0MRW<DB0ERF<DB0HGW<ON0DXC<ON0RET<DB0RES<ON0AR<ZL2BAU<
VK3AYM<VK3APC<VK3KAY
Sent: 050102/0358Z @:VK3KAY.#WEV.VIC.AUS.OC #:34601 [Wendouree] $:34601_VK3KAY
From: VK3ABK@VK3KAY.#WEV.VIC.AUS.OC
To : ANTENA@WW
Hello all Serious Thinkers!
In a bulletin titled 'Antennas and why?' I hit the wrong key in stating the
'Impedance of Free Space'. I meant to say '377 Ohm'. Not 277 Ohm.
Thanks Andy, GM7HUD, for the observation. A 'serious' reader!
For the record, the computation of the impedance takes into consideration
the Permeability and the Permitivity of free space.
The permeability being.... 4ã X 10^-7 Henry per metre
The Permitivity is given by....8.86 X 10^-12 Farad per metre.
Calculating the square root of Permeability/Permitivity gives 377 Ohm
As a matter of interest, using these values of Permeability and Permitivity
in the equation...
1
v = ÄÄÄÄÄÄÄÄ
sq root (æ x î) (Permeability x Permitivity)
Gives very nearly the speed of light (v) in a vacuum (space).
See how Einstein's ghost keeps getting involved in our radio waves!
The important thing to understand is that we need to 'launch' our RF energy
into a 'conveyance' which propogates through space and which the early
thinkers dubbed an 'aether' (ether) as an convenient explanation.
73. Dick. VK3ABK.
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