SNAP Layout & Construction

Chuck Adams, K7QO designed the SNAP circuit to be a simple-yet-effective 2N2222A based crystal-controlled oscillator with a low pass filter on its output. With the components shown in the schematic, the circuit delivers a very clean 10-to-30 milliwatt RF signal into the 51-ohm load resistor.

The 2N2222A transistor oscillates at the fundamental frequency of the crystal and delivers its signal through the 4:1 step-down impedance-matching transformer T1 to the low pass pi filter designed for this frequency. The 51-ohm load resistor properly terminates the filter and the RF power is measured at this resistor.

For an excellent description of typical amplifier and oscillator circuits used in similar configurations as the SNAP, refer to Solid State Circuit Design, published in 1996 by the ARRL, written by Wes Hayward and Doug DeMaw. The first two chapters are an outstanding reference for transistor biasing and interfacing design.

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