The second gate (G2) of a MOSFET can be used to incorporate a crystal oscillator into the same stage as a frequency mixer. Although old hat with tubes, this scheme is seldom seen in dual-gate MOSFET circuitry. L3, 03, and XI form the crystal oscillator, and T2 is an IF output transformer. T1 and 01 are tuned to the converter input frequency.
This circuit should be useable up to 25 MHz or so, or higher with third- overtone crystals.