Chapter 3 question about the bfo design

[ugocapeto]

It seems to me the oscillator design is colpitts LC tank usin a common base transistor amplifier but then i am quite confused because the base is not ac grounded in the schematics. What am i missing? Thanks in advance for any answer, i appreciate your time.

[Carl-NC]

The base is DC-biased to about 3V so for practical purposes it is an AC ground, albeit with 32k of resistance. You can place a cap across one of the resistors if you want a lower impedance AC ground but I doubt it will make any difference.