# how to measure the gain of two identical antenna

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#### abc123

##### Member level 4 How do I measure the antenna gain of a new antenna without using the reference dipole antenna. some one told me that it is possible to use two identical antenna one for transmission and the other for receiving then divide the signal loss by two to do it (without using reference antenna).

Is it possible?

#### kspalla Make the test setup for transmitting a signal annd receive the same at a known distance.
Use the equations from link given below.
https://www.bbc.co.uk/dna/h2g2/A743861
solve for gain.

Let me know if you need asistance.

#### abc123

##### Member level 4 kspalla said:
Make the test setup for transmitting a signal annd receive the same at a known distance.
Use the equations from link given below.
https://www.bbc.co.uk/dna/h2g2/A743861
solve for gain.

Let me know if you need asistance.

"kspalla" some confusing on the equation. if I put two antenna at some fix distance, one connected to the signal generator, the other to power meter, I record the transmitting power, and receiving power, what is the lambda, sigma, and MDS should I use? is the distance related to Tx frequency?

say tx power = 0dBm, distance = 50cm, rx power=-20dBm.

#### AndyECE

##### Member level 5 Point the antennas directly at eachother.
Assume you know the following:
Transmit power (Pt)
Distance (r)
Wavelength(l)

and assuming the gain on each is the same, you get

G = ((Pr/Pt)^0.5)*4*pi*r/l

easy enough. I have performed this exact measurement to do the same thing. I had two identical antennas, and this worked just fine.

The distance and Tx frequency are not really related. Over long distance, they would technically attenuate differently, but inside a lab this is not appreciable.

Of course antenna gain is itself very dependent on wavelength. In general, higher frequency means higher gain for a given antenna (but only to a point; the antenna only has a certain range of lambas it can actually propogate)

Points: 2