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Bredhurst Receiving and Transmitting Society

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Part 2

Practical 10.

Simple frequency calibration

Calibrate a variable frequency oscillator (VFO) employing an adjustable tuned circuit. Calibration to show the relevant amateur band edges. The VFO may form part of the project to satisfy 10e.1, or be part of a previously constructed project or provided by the assessor.

Those students taking a course with the BRATS will have the oscillator provided together with all the other equipment needed to perform this task.

The circuit diagram used for the prototype test piece is a development of the circuit shown in the Technical Basic as follows  :-

The power is supplied from a 9v battery and to ensure stability the 6.8V zener is used with a limit resistor R1, C5 is to further ensure the stability of the circuit and not currently used in the prototype.


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