"Andrew Holme" wrote in message
...
I'm playing with super-regenerative oscillators in LTSpice.

My question concerns the 230XP valve VHF super-regenerative oscillator in
this figure 8.9:

http://www.holmea.demon.co.uk/temp/duplex.jpg

Here's figure 8.11 from the same book:

http://www.holmea.demon.co.uk/temp/iff.jpg

The text reads: "the super-regenerative oscillator in figure 8.11 is a
triode valve connected in a commonly used high-frequency circuit of the
Hartley type which relies on the internal capacities of the valve for its
operation." Why is it a Hartley when the tap is fed through an RFC?

Does the 230XP oscillator in figure 8.9 also rely on internal valve
capacities? How do these oscillators work? What is special about tuning
capacitor C in figure 8.11? What is the role of the cathode chokes?

I've been playing with JFET oscillator circuits in LTSpice and I can't get
them to oscillate unless the LC network between drain and gate creates a
phase inversion. How do these valve circuits make 0 (or 360 degrees) of
phase shift around the loop?

What is the nearest semiconductor equivalent of the above valve circuits?
Below is a JFET oscillator with feedback from drain to gate; but no
reliance on parasitic capacities, although I'm sure they affect the
frequency. Is this an LC Pierce?

http://www.holmea.demon.co.uk/temp/osc.asc

TIA
Andrew.


I'm wondering if they're actually common-grid oscillators relying on
anode-to-cathode parasitic capacitance. This circuit oscillates:

http://www.holmea.demon.co.uk/temp/osc2.gif