# output power of rf transmitter?

#### whale

Joined Dec 21, 2008
111
hello,

can any one teach me how to calculate output power of rf transmitter?

iam very much confused in measuring power in open air .

#### beenthere

Joined Apr 20, 2004
15,808

#### KL7AJ

Joined Nov 4, 2008
2,208
hello,

can any one teach me how to calculate output power of rf transmitter?

iam very much confused in measuring power in open air .

Greetings:

Without a load of some sort, a transmitter is nothing but a voltage source with some value of fixed equivalent resistance in series (commonly 50 ohms). Maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance.

A simple way of actually measuring power is by measuring the R.F. voltage across a load resistance. Power=e^2/R

Eric

#### whale

Joined Dec 21, 2008
111
can i consider my load as a capacitor?
so that impedance will be capacitive reactance , iam i right?
so that power will be e^2/capacitive reactance.

#### KL7AJ

Joined Nov 4, 2008
2,208
can i consider my load as a capacitor?
so that impedance will be capacitive reactance , iam i right?
so that power will be e^2/capacitive reactance.
That will be mainly true for your situation. At a high enough frequency, you may have some radiation resistance as well. What is the application of this transmitter?

eric