[time-nuts] Vintage Frequency Measurement

Bob Camp kb8tq at n1k.org
Mon Feb 13 18:46:43 EST 2017


With a VFO running, you have a heterodyne frequency meter. That is (at least to me)
a very different device than an absorption wave meter. I know way to put power into
a BC-221 and use it as an absorption device. 

I’m not in any way saying that the LM or the 221 are less useful. They are still to this day
great little boxes. The just aren’t (by my understanding) wave meters. That term describes
a different device that works a different way. 


> On Feb 13, 2017, at 5:52 PM, John Miles <john at miles.io> wrote:
> 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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