How to measure the air impedance?

[mr_byte31]

1-how can i measure the air impedance
2- i have a circuit (RF circuit ) i want to make matching with the air impedance
can any body help me to make the output impedance of the circuit = to that of the air ?

 

[kishore2k4]

Re: impedance of air

Characteristic impedance of free space is approximately 120pi ohms, for air it is almost the same or slightly less in humid environments.

I am no expert but you match the circuit's impedance to that of the radiating antenna instead of air?

 

[mr_byte31]

impedance of air

i know that
if the enviroment conditions changes
the impedance changes
the question was
i want to measure the impedance at this conditions

 

[flatulent]

Re: impedance of air

The magnetic permeability does not change with conditions. It is the capacitive permittivity that changes. You can measure the capacitance of parallel plates and back out the permittivity to do the impedance calculations.

 

[Mansour_M]

Re: impedance of air

Hi Dear mr_byte31!

the impedance of Free Space is about 377 Ohms. and when the conditions change this amount will be less than 377 Ohms.
You can't measure this impedance by an Ohm meter or something like that. This impedance is used to express the relation between Electric and Magnetic Field Traveling as a Wave.
Why do you want to match your circit to air? Do need to transmit the signal to some where? If the answer is yes you should use an antenna.

Thanks!

 

[nhomuathu_hanoi]

Re: impedance of air

We are well known that Characteristic Impedance of the air is calculated by:
Z0 = sqrt(u0/e0) =~ 120pi.
I think, if you want to measure this characterisctic impedance, you should measure pemitivity and permeability of the air, that provides you air characteristic impedance.
You can not measure it directly, I think because, simple, it's characteristic quantity.

regards!

 

[mr_byte31]

impedance of air

thank u every body
now i understand