Interesting Signal Generator Circuit

I saw this issue of Radio-Electronics magazine from November 1972 on the always interesting Worldradiohistory site:

https://www.worldradiohistory.com/Archive-Radio-Electronics/70s/1972/Radio-Electronics-1972-11.pdf

The article that caught my eye was on signal generators on pdf file page 49.  Here is the schematic of author Huffman's design:

The circuit uses three Colpitts oscillator transistors which are powered via one section of a three position band switch.  The other section of the band switch connected each oscillator output to a buffer amplifier AND the 365 pF tuning cap.  This multiple oscillator approach is easy with transistors but a huge problem with tubes cost wise.  One other item: B&W Miniductor coils are used instead of either toroids or slug tuned coils.  It is much easier to wind a solenoid air-core coil than try to create a slug tuned inductor from scratch !  Also, Miniductors are still available !

https://www.bwantennas.com/Mini.html

I had blogged this band switched VFO before:

https://wb9kzy.blogspot.com/2024/08/it-was-best-of-times.html

One of the reasons why I never built the VFO was that 5 section custom rotary switch.  In the VFO there are actually two different variable 365 pF caps (a ganged unit) but a single Colpitts oscillator transistor.

Band switching isn't easy, especially with an HF transceiver with 8 bands - complicated multi-section switches aren't used but from what I can hear it's done mostly with relays.  It's ironic that a "modern" solid state rig might have a gazillion relays but an old tube rig might have just one relay.

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