
232 Analog Electronics
characteristics (Figure 9.14b). These advantages
do not come without an appropriate price tag, in
that the SC crystal is more difficult and expensive
to produce and has more spurious modes than
other crystal types. For example, the 10 MHz SC
crystal used in the Hewlett-Packard 10811A/B
ovened reference oscillator is designed to run in
the third-overtone C mode resonance. The third-
overtone Β mode resonance is at 10.9 MHz, the
fundamental A mode is at 7 MHz, and below that
are the strong fundamental Β and C modes. The
circuit of Figure 9.14c shows the SC cut crystal in
the 1081 lA/B oscillator connected in what is
basicall ...