VFO/BUFFER circuit


Posted on Feb 6, 2014

It`s basically a standard Hartley oscillator, output is +7 dBm into 50 Ohms. Don`t be tempted to add a gate diode, this circuit doesn`t need it, and it will degrade the phase noise performance, according to Ulrich Rohde. It should be suitable for any frequency up to 10 MHz or more (depending on how good you are at making drift-free oscillators) and may be tuned with a suitable capacitor or varicap tuning diode.


VFO/BUFFER circuit
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It`s essential that this circuit be built into a suitable screened enclosure if using it with a DC receiver, and steps be taken to ensure that as little as possible of the oscillator signal can get into the receiver input, to minimise hum and microphonics. This won`t be required if the oscillator is run at half the input frequency, and put through a balanced doubler, as is done with the Kanga US version of Campbell`s binaural receiver.




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