I put the n920 slave in a box and left it with a co-worker on the fifth floor of my office building. I took my laptop and the master radio over to our other building, 5 km away, and set up on the sixth floor. My co-worker was on the balcony outside the building, and I was in a conference room inside.
After we powered up the radios, and after I dealt with my radio coming loose from its dev board, we established a link and I was able to send a few characters to the slave. It was set up with a loopback connector, so those bytes came right back.
A query of the master's receive signal strength returned -91 dBm.
Hopefully this weekend we can do a 20 km test.