Radio Frequency Location Beacons Losing rockets is a major occupational hazard if you are interested in high altitude flight. It can also be exceedingly expensive if you have onboard avionics payloads such as altimeter/accelerometers and timers. This is where having an onboard radio frequency location beacon can save the day. The design used here was inspired by Peter Kerckhoff's excellent PbP web pages, and borrows heavily from the details on his web site. A 433 MHz transmitter module with an output power of 10mW is used as the radio transmitter, with a pulsed tone output being transmitted via a timer circuit consisting of 2 x 555 timer ICs. The 433 MHz frequency has the advantage of requiring a small antenna for the receiver, and is also a legally acceptable frequency for use in the U.K. A frequency of 418 MHz could also have been used, but since that frequency is being encroached upon by a new commercial radio system over the next few years, it made more sense to go for the 433 MHz frequency.