Knight Transistor Code Practice Oscillator 83 Y 239

from the 1960 Allied catalog

manual: http://www.n4mw.com/cp026.pdf

schematic source (page 21): https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Technology-General/Allied-Radio-Circuit-Handbook-6th-Edition-1961.pdf

This was Allied - Knightkit's first transistorized Code Practice Oscillator (CPO).  Interestingly to me, it uses an audio tickler coil type of oscillator.  The Allied people had access to relatively inexpensive audio transformers so one is employed here to provide the main coil (for the LC oscillator) as well as the tickler feedback coil.  The CPO manual above had a tiny version of the schematic but the Allied kit builders booklet did have a more visible one:

The transistor is the famous CK-722 - a PNP Germanium transistor.  High or low impedance headphones could be used with this CPO.  Apparently the result was very low power consumption, the manual says 30 weeks of continuous operation with a fresh AA cell !

The later LC-1 CPO (which I have) used a 2 transistor oscillator which could drive a dynamic speaker - it also had a light but used a C cell so probably not claiming 30 weeks of continuous operation !

Semi-obligatory inflated price:

I will have to puzzle out how to implement this with 21st century components (I never bought any CK-722 transistors, they had become harder to find in the 1960s).

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm