Understanding the Michigan Mighty Mite
Redraw the Michigan Mighty Mite so that it conforms to the Pierce oscillator circuit. The similarity should be obvious. R2 has been ommited in the MMM circuit...Q2 is operating at much higher current than the small-signal Pierce.

The antenna-coupled link winding on MMM's L2 has been omitted, and the key switch in series with R4 (27 ohm) is replaced with a short circuit:







simulate this circuit &ndash; Schematic created using CircuitLab
In both circuits, the crystal feeds back radio frequency signal from transistor output (collector), to transistor input (base). The high-impedance collector load of the RFC choke in the Pierce oscillator has been replaced with a parallel resonant LC circuit in the MMM (L2 in parallel with 365 pf).

The MMM is a power oscillator that puts out more power when L2 is connected to the collector through a tap, rather than going to L2's high-impedance end (where it meets the crystal).

Thinking black-and-white about a series-resonant crystal versus parallel-resonant crystal gets you into a bit of trouble. Most crystal oscillators will give you an output frequency that lies somewhere between the lower-frequency series resonance, and slightly higher-frequency parallel resonance.

A 2N3904 is perfectly fine for Q1 in the low-power Pierce oscillator, but would likely overheat in the MMM circuit (Q2). A bigger transistor should be used, likely with a top-hat heat sink.