[time-nuts] Vintage Frequency Measurement

John Miles john at miles.io
Mon Feb 13 17:52:17 EST 2017

You could use it as an absorption wavemeter, in its broadest sense of a passive tuned circuit with an indicating load.  The headphone jack was normally used to calibrate the VFO against a harmonic of the internal crystal oscillator, but it could zero beat an external source as well.  It stretches the nomenclature but the job still gets done.

Even as late as the 1980s a BC-221 (or LM-10 in my case) was a useful piece of gear.  As Bill suggests, all the qualities needed for indulgence in time/frequency nuttery were present.  They were incredibly expensive to build, being engineered to survive bombs that hadn't even been invented yet, and they could perform at levels beyond any reasonable requirement.  I used one for frequency spotting on my even-older Philco console.  

Just the other day, I visited the Spark Museum in Bellingham, WA, and was amused to see one over by the 'Titanic' exhibit.  Not a curation mistake on their part, just a consequence of having more cool stuff than exhibit space.  I had to restrain myself from reaching down and giving the dial a tweak.

-- john, KE5FX
Miles Design LLC

> Hi Bob:
> The BC-221 is usually referred to as either a Frequency Meter or a
> Heterodyne Frequency Meter.

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