I would like to understand how well different antenna turn electrical power from my battery into clean radiation to a far off receiver. Testing SWR only tells me something about impedance matching, but how much does it tell me about antenna efficiency or ability send RF out. For example, I compared two dual band antenna in UHF mode, using all the same equipment to drive the antenna, the same location, etc., the only variable is the antenna. Remotely, let's say 25 yards away, I had a field strength meter with it's dipole rabbit ear antenna tuned to roughly half wavelength. I verified with my handheld that the meter needle responds to a TX push from my handheld, and that response drops off with frequency adjustments up and down from the 'center frequency'. So I'd say the meter needle is not an absolute dBm measurement, but a decent relative comparison. I go back to the truck and swap out antenna, and I see that one antenna barely moves the needle, while the other moves the needle about 20x that amount. Again all else remains exactly the same. Question 1: Is this a fair test of these two antenna radiating efficiency/capability? Is there anything I should do differently? Question 2: The antenna that fared worse on transmit does seem to also not receive weak UHF stations as well as the antenna that fared better. This is anecdotal, and not measured carefully at all. In this case, the two antenna are mounted in different locations in the vehicle (though the poor performing antenna enjoys a higher mount, with excellent ground plane, while the better performing antenna is lower and poor ground plane, for this test). Is it true that if an antenna doesn't transmit as well as another, all things being equal, that it also won't receive as well either? Some rule of reciprocity? Thanks for any insight. Basically, after having drilled holes in my roof, sprung for good cables, mountes, radios, etc... I want to find an antenna that pumps out max RF power to the intended receivers. And SWR is fine, it's one data point, but don't we really want to see how much power is going into the air, at the end of the day?