VCO:  Franklin 80Mhz-180Mhz

Dec 22, 2011

Parallel  Tank Franklin Oscillator use zero phase shift by 2 stage invert amplifier. the amplifier gain is high, so it possible highly isolate the tank. C4,C1 is very small and high high reactances at the resonant frequency.

* this a revised circuit original write  by Iulian Rosu, YO3DAC – VA3IUL,

* Franklin Oscillator had very power amp to enable lightly couple to tank, so tank's Q  is preserved when connect to active device.

* easy to oscillate in a widely frequency range, but tune range is limited by total capacitance and the tune range of the D2

* T1, T2 work in A class, make it stable of frequency: to achive this goal, reduce C4, C1 to just start oscillate.

* A buffer stage is recommanded, because signal  directly get from tank itself.

* use this circuit, oscillated from 80Mhz to 180Mhz( change Air Coil)

* for higher frequncy, need reduce L1, otherwise it might oscillating at a strange frequency(should cause by distribute parameter)

here is the quick assemble layout and the final under test Franklin oscillator.

finised@ Jan 30, 2012.

VCO linearity @2013/10/18

use one BB910, from 11V, frequency grow is lowing down.