I'm having trouble making sense out of this requirement, in terms of how to test for it.

I have a specification stating that for an RF power level measured in dBmi (let's call that power level S dBmi), a specific result should be obtained in a test.

As part of that test, I have a receive antenna that I must use and it is not isotropic. Not only that, it includes gain and loss internally, so its performance is just not a matter of the beam shape. A measurement at its output would include its pattern gain and its internal gains and losses.

There is a passive transmit antenna of known gain at a known distance away and a controllable signal source suitable for producing the required signal. (Let's assume it's a CW signal, to keep it simple.)

How would I set up for that test? How and where would I verify that the RF signal level is correct?

I assume the requirement means that if I had an ideal isotropic antenna, with no internal gain or loss, then the RF power measured at its output should be the specified level S in dBm (where the "i" for isotropic is now implicit in the setup). If that's the case, I could just measure the RF signal at the antenna output and radiate from a source at the power level that meets that requirement.

But where do I go from there? I can calibrate using passive antennas, like horns, but ultimately, I need to know how to set this up with the required antenna.

  • 1
    \$\begingroup\$ It would help if you make for us a drawing, where the device under test is clearly pointed and what is the wire from where SdBmi output is required or into which wire you should be able to feed SdBmi. What is possible to adjust and what should be fixed? Which antenna is that one whose gain should be taken into the account when converting dBm values to dBmi values? \$\endgroup\$
    – user136077
    Aug 13, 2018 at 22:06

1 Answer 1


Without knowing what is the DUT and where the power level should be SdBmi, I guess:

You have a precision signal generator as your transmitter, it's connected to an antenna A which should be at certain distance from your receiving antenna B. Antenna A has gain XdB. You direct A and B against each other, input to A power (S-X)dBm and check if the machine which is connected to B, works as wanted. I assume B is part of the device under test.


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