Thanks for the reply and the advice. I will look into FSK. The reason I can't use IR or directional antennas is that the device will not always remain in place and most likely will not have line of sight.

Side note:
I worked as a flight test instrumentation engineer for the Skunk Works for 30 years and had a lot of unique telemetry problems/fixes on aircraft. The difference with my experience and what I'm trying to do now is that I don't have $80K+ to spend on telemetry equipment like I did in those days