[time-nuts] Advanced 5 to 10 MHz doubler
bruce.griffiths at xtra.co.nz
Tue Feb 15 11:31:05 UTC 2011
Paramithiotti, Luciano Paolo S wrote:
> Best regards, Luciano
> Luciano P. S. Paramithiotti
This design appears to have gone somewhat astray.
Adjusting the 200 ohm pot between the collectors should have very little
effect if the doubler is operating correctly as the collector nodes
should be high impedance unless of course the transistors enter
saturation in which case the phase noise performance will be severely
The best place for a balance adjustment circuit is actually in the
The description of the biasing is misleading in that the actual bias
level that sets the crossover current is determined by the signal
dependent voltage across the two 0.1uF capacitors in the emitter.
With a 1:1 input transformer the quoted figure of 35 ohms for the input
impedance seems excessive for large signal operation of the CB stages
unless of course they saturate.
It would also appear that the 20MHz tank 5.6uH + 12pF as drawn is
inappropriate in that it inevitably leads to saturated operation.
A series resonant 20MHz tank from the collector node to ground would be
a better choice.
A snapshot or even a sketch of the collector voltage waveforms would be
useful in showing that the transistors saturate or not.
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