[Milsurplus] BC-221 - Another Question

[Tom Brent]

What was the contract date for the first military BC-221? I ask because
there is a Bendix aviation radio catalog (copyright 1940) online that shows
a commercially available frequency meter which appears to be a clone of the
BC-221. It is identified as the "*Model IF-12 Portable Frequency Indicator
Equipment*" and a 19 inch rack mount version (Model IF-9) is also shown.
Did Bendix copy the military BC-221 and market it to commercial aviation or
is the BC-221 a copy of the IF-12?

Interestingly, the catalog also shows a model MN-13 loop amplifier that
looks very similar to the USN model DU and DW loop antenna/amplifier except
for the fact it uses an external MN-20 loop and MN-52 azimuth indicator.

Regards,
Tom
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