Small transparent serial telemetry radios are a core part of many projects, and play a key role in amateur UAV systems. Unfortunately popular telemetry radios, such as the widely Xbee line of radios, provide poor range and the lack of source code for the radio firmware makes protocol improvements difficult.

This first half of this talk will describe a project to build a telemetry radio system with an open firmware, and hardware that supports much longer ranges than comparibly priced existing systems. The open firmware includes features like frequency hopping, time division multiplexing and support for a wide range of regulatory additions such as listen before talk.

Once you have a good long range telemetry system you need some higher level protocols to run over it. The second half of this talk will focus on the problems of reliable transmission over the telemetry link, looking at why TCP performs poorly in the face of large amounts of packet loss. An anternative block oriented transport, implemented in Python on Linux, is discussed which provides much better performance for reliable transmission of image and command data over the telemetry link.