The crystals are 10.7 MHz similar to Regency type but with a different load capacity. Regency crystals should work but may be a bit off frequency. The difference probably is not significant in practice.
Thank you. Subsequent to my post, I went on an internet search re: crystals. Here's what I found:
"Although they used a 10.7 MHz first IF, Sonar radios require
parallel resonant crystals different from the common series
resonant crystals used in Regency and Radio Shack scanners.
Some Radio Shack crystals will work in Sonar units, but more
often they oscillate a few kHz off frequency and are
unsuitable unless changes are made to the oscillator
circuitry.
Therefore, beginners should avoid these radios."
Harrumph!
Time to dig into my repository of Regency/Radio Hack/Bearcat Crystals. Stay tuned for further details as they become available.
