Armstrong, Hartley, Colpitts, Clapp, Wallin...

Posted: 12/31/2020 6:12:23 PM
Buggins

From: Theremin Motherland

Joined: 3/16/2017

RC PLL doesn't look good enough.

Trying to design custom one.

VCO will have the same schematics as main oscillator. LC should give stable noise free performance.
Stuck trying to turn current sense oscillator into voltage controlled one.
BBY65-02 varistor parameters look fine, but I cannot figure out how to change frequency using it.
Probably, high LC swing may be a problem.

Posted: 12/31/2020 7:08:35 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"It's suitable only for drive signal range 0.7..VCC-0.7V. W/o load it's output looks like rail-to-rail, but under load it's getting limited by 0.7V offset."  - Buggins

High voltage is fun, but honestly, once you've got ~100Vpp at the antenna, any more is probably diminishing returns.  Way off resonance, the buffer provides the proper duty cycle to return to the lock state over a very wide range and through multiple sub harmonics, which is not usually the case for an XOR PLL, and is way more valuable than super high antenna voltage IMO.  You do want to use the XOR phase detector because it is relatively immune to edge noise.

"Phase is locked near 0, using phase comparator 2."

Don't you want a 90 degree lock for the XOR phase detector?  C divider will give you that.

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