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NOTE! It takes some time to stabilize. To get it going depress the switch for a couple of seconds and let rip!
Okay so what seems to be true with this simulation circuit is the possible increase by ten fold of output voltage swing. This is done by placing a third cap to ground below the buzzer (feedback cap) that's wrapped around the collector and emitter.
UPDATE! After experimentation with this circuit at VHF frequencies, it seems that the value of the emitter cap can be raised to 1nF. In so doing, this oscillator produces a peak swing of plus and minus the rail voltage.
Note: I have lowered the supply to 3 volts. This puts the transistor into a zone of operation that promotes more stability. I have tested this circuit carefully. It will run for weeks without drifting more than a few HZ! This is amazing considering there is NO crystal or resonator.
HOW TO BUILD IT
(Please also read my comments posted in response to @usernames)
WARNING!!!
Do not use veroboard or solderless breadboards! At VHF the capacitance and inductance, created by these rapid prototyping systems, will strongly affect the circuit. Instead use plane copper PCB material. You can get this from an electronics supplier or from EBAY.
Mount all the components using what's called Manhattan style construction. Check you tube, etc
Keep all the leads as short as possible. The complete circuit should be no bigger than 3 X 3 CM.
You do NOT need the switch (shown on the simulation). The oscillator will start perfectly well without this.
How to make the coil ( inductor )
Wind 6 turns of 0.5 mm copper single core wire over a 3 mm drill bit. Then space or pull out the coil so it is appropriately 5 mm in length. If you are not using enamelled or otherwise insulated wire this is OK, but make sure that the windings do not touch each other.
The capacitor and resistor values in the simulation will have to be brought to the nearest standard value available and this will work fine within a 10% approximation. You can use a 2n2222, 2n3904 or similar transistor.
NOT SURE ITS A COLLPITS!
My understanding is that a true collpits uses two capacitors as a kind of impedance division; the feedback is applied without loading the circuit too much.
This is the reason for saying that this might not be considered as a true collpits oscillator. you can remove the lowest capacitor and the oscillator will function. Above the lowest capacitor is the capacitor that creates feedback. However this might be thought of as a kind of uncontrolled buzzer. Without the tank circuit above the oscillator is un - tuned out of control and useless. I am sure that @hurz will say that if we move the components around we will see a phase delay or impedance divider circuit created from the 20pf across the emitter and collector. I have had to increase my normal value of cap here from 10pf to 20pf as the transistor has capacitance which seems to be in series with the cap and thus lowers the effective value rather than increasing it as would be intuitive from a glance at this circuit!
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