Just a quick follow up. Many of these radios are FM based and an RF service monitor will easily measure the 12 dB sinad sensitivity if you connect to the discriminator output (if you can get at it). Alternately badger your vendor until they give you a sensitivity spec that is at least measured in the right "dimensional" units. your class of reciver should be 0.5 to 5 uV or -100 to -115 dBm.

When you have the senesitivity spec, go to my website at http://www.aria-glb.com/wireless/som.php4 and run the range and signal loss calculator. Plug in you freq in MHz and use 0.5 dB for the line losses and 0 dB for your TX and RX antenna gains. Your 1W radio is +30 dBm. Plug in different miles miles until you run out of operating margin and you get your maximum theoretical gain.

Of course you never want to run at the limit and most systems want to see 15 to 20 dB of safe operating margin so that if the plane banks , you can withstand an antenna directivity induced loss. Happy to answer any questions....