Using the GPS Satellite system offers the advantage of very accurate timing and by extension, frequency control. The long term error is to all intents and purposes zero, with time and frequency accuracy being comparable to the international standard. The traditional route is to use a relatively low cost GPS receiver module which outputs a 1 Pulse per second signal (1 PPS) aligned to UTC. Basic GPS modules such as the Garmin GPS25 and Motorola Oncore have been around for some years and are available at low cost. It is possible to phase lock a divided down crystal oscillator to this 1 PPS signal and transfer its long term stability to , say, a 10MHz reference which is subsequently used for deriving any LO and beacon frequencies. The subsequent PLL system is usually described as a GPS Disciplined Oscillator rather than locked, since it is not, strictly speaking, actually ‘locked’ to the GPS system at all; just controlled by it via the 1 PPS generated by software in the receiver module.
Build Accurate LC Meter and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging and reset function to make sure the readings are as accurate as possible ... [more]