# Two-Antenna Method for Gain Calculation

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1. Oct 21, 2014

### kahn

Can someone please help me understand how two-antenna method is used to measure gain of an antenna ?
I could't even find literature on it, please if anyone could even suggest any document that would also be great.

Thanks.

2. Oct 21, 2014

### sandy.bridge

Pozar derives it in his Antenna chapter.
$$\frac{P_r}{P_t}=(\frac{\lambda}{4r\pi})^2G_rG_t$$

3. Oct 22, 2014

### sophiecentaur

This is a highly problematical business and you can seldom be really sure of your answers until you actually start to use the antenna in a working system.
That looks OK as a bit of theory and assumes the antennae are in free space and the test antenna has a known gain. For a practical way, you really need some indication of the radiation pattern of the antenna under test or at least to ascertain that local conditions are not affecting use of that formula.
If you are dealing with two very directive antennae (e.g.dishes) and well elevated about the ground) and if they are well matched to your test equipment then that formula would be more reliable.