CB Radio 11m data telemetry

June 2, 2024

Mid-range radio control (1 km to 10+ km) and other data telemetry has long been legal in the 27 MHz 11m band across the world. In the USA, FCC Rules Part 95 subpart C addresses 27 MHz data transmissions. 27 MHz is still actively used for data telemetry, with manufacturers claiming up to 15 miles range with a 10 Watt 27.255 MHz data FSK transceiver. Another long-time 27 MHz data telemetry application is 27 MHz paging.

Wireless mice and keyboards in the early 2000’s decade widely used the 27 MHz band. Unfortunately those devices operating on 27.195 MHz “19A” would significantly interfere with the popular CB channel 19 27.185 MHz, and could be heard even just driving by a house with a CB radio in the vehicle. Likewise for the other 27 MHz channels that bleed across several CB radio channels if in a neighboring house or passing within say 50 meters of a CB radio. This is due to the liberal emissions mask of FCC Part 95.779(a) allowing significant bleedover of unwanted modulation products into adjacent channels. Thankfully, these 27 MHz mice and keyboards have limited users these days. 27 MHz mice and keyboards are still sold as low-end inexpensive devices, so they might still be heard in some locales.

The data telemetry or mouse/keyboard transmissions typically use FSK modulation. On an AM receiver, FSK might sound like a quiet transmission with little modulation. Using an FM receiver, FSK typically sounds like a loud buzz or tone.