Its hard to beat the cost and versatility of the ubiquitous RTL-SDR dongles, but the temperature stability of their reference oscillators isn’t sufficient for some applications. While the internal 28.8MHz quartz crystal in these units can be replaced by a high qualitytemperature compensatedoscillator, these tend to be relatively expensive and/or difficult to source.
Here’s a scratch-built 28.8MHz TCXO capable of +-1ppm stability from 0C-55C; best of all, it’s not only easy to build, but is designed entirely from readily available and inexpensive components. For improved temperature stability, the main oscillator can even be replaced with one of many commercially available TCXOs!
Today we explore the use of oscillator synthesis software (Genesys) for practical crystal oscillator design, and the impact of the Randall-Hock correction formula on linear open loop analysis accuracy.
Today we look at how to generate a pair of quadrature signals from the output of a crystal oscillator using a pair of d-type flip-flops, as well as discussing the advantages and disadvantages of this technique.
Ever wonder what goes in to the design of a crystal oscillator? We’ll examine the operational theory of crystal oscillators, and design a discrete Pierce crystal oscillator suitable for use as a local oscillator in an HF receiver.
My discrete Pierce oscillator design tool can be found here; references and additional reading are listed below!
Oscillator circuit design and crystal loaded Q analysis