Re: [IRCA] Yes, SAH!

[Bruce Portzer <bportzer@xxxxxxxxxxx>]

The US military had several different types of frequency meters.  The 
Navy had an LM-xx series of similar units.  I had an LM-14 that I bought 
in the mid 70s for about $25.  It operated like the BC-221 but the 
packaging was different - the booklet was stored in a little slot at the 
bottom and it had shock mounts for ship/aircraft use.  I generally 
ignored the booklet and instead used my frequency counter to find out 
the frequency. 

Bruce
> Yes, it was indeed the BC-221  -unless my memory is totally
> out of sync. This was a low frequency linear-tuning oscillator
> in a case roughly the size of a soccer ball. It used a precision
> vernier tuning knob with a very accurate vernier scale readout.
>
> A legacy of the engineering effort carried forth during WW II.
>
> This device was meant to be linear but in practice they could
> never be made that precisely, so the BC221 came with a little
> booklet, built into the case lid cover, that showed the slight tuning
> variations and inperfections. It was used as a transfer oscillator,
> you could tune the 221 to zero-beat the unknown signal, then by
> reading the tuning knob scale and applying the correction
> factor from the chart book, get a good idea of the real frequency.
> Naturally each such booklet was custom-created for that
> particular device, using a reference whose type I don't know.
>
> I honestly don't remember how accurately they could be trusted,
> but 1 Hz seems reasonable. I remember seeing these being
> offered for sale w/o the chart books, no one wanted those.
>
>   
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