[Milsurplus] BC-221

Tue, 16 Dec 2003 11:33:54 -0500 (EST)

> I DO  NOT celebrate diversity

> transistor-ish stuff on one side of room, 'traditionals' on other -
  how gets 'traditionals' on freq.?

Easy say I, & interpolation freq. meter not on recipe.  Just set 
transistor-ish set to desired freq. & w/o antenna connected to 
same, tune up 'traditional' & dial in freq. 'til big whoop heard in 
transistor-ish set.  Crude, direct, effective.

How else do you get a FBX & a p-p Hartley to play together in AWA 'test?

Now, a delayed echo on how BC-221s calibrated.  SUPER neat.

=====>

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Date: Thu, 09 Mar 2000 16:41:45 -0500
From: Jerry Proc <[email protected]>
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Hi Folks,

The original question asked by PA3FVQ about the BC221 was how the
factory calibrated the BC221 and not how to re-produce a missing
calibration book for an existing BC221. Thanks to everyone who
responded. Here is the definitive answer to the question as supplied
by Geoff Fors WB6NVH.

*************
Jerry-

I am just a digest-reader of Boatanchors so cannot directly post a reply 
to the group concerning the inquiry you forwarded from PA3FVQ about the
BC-221.I sent him the reply below; perhaps you or the list will find
it of interest:

-----Original Message-----
From: Geoff Fors <[email protected]>
To: [email protected] <[email protected]>
Date: Thursday, March 09, 2000 12:16 PM
Subject: SCR-211/BC-221 Calibration at factory

Hello Jan-

I noticed your inquiry on the Boatanchors reflector regarding how the
BC-221 frequency meters  were calibrated in production.

Would it surprise you to learn it was done by computer ?  An automatic
calibration computer using 126 tubes was developed by engineers at the
Philco Corporation, Research Division, Engineering Department to handle
this task.  It consisted of an automatic calibrator combined with an
adding machine (semi-automatic) which recorded the calibration data at 327
points, interpolated between those points, and automatically printed
the 3252 different frequency value numbers in each individual 
calibration book.

The time to do all this was 6.5 hours, the actual printing of the values
in the book taking just 16 minutes.  The time for an experienced human
to do the work manually, in contrast, was averaged at 16 hours per frequency
meter.

A mechanical hand automatically turned the dial of the BC-221 to various
pre-determined settings while measurements were underway.  The
calculations were carried out by automated complex adding machines of
the type then used by banks and finance companies, and the results 
printed in the calibration book and also saved on paper tape.  The adding 
machines were fitted with solenoids to depress the keys; the tubes 
the "computer" used were mainly 0A4G's.

Presumably Philco shared this technology with Zenith and the other makes
of the frequency meter.  I suspect that the original production runs
of the BC-221 were calibrated manually, and that the computer system was a
mid-wartime development, in operation by at least mid-1942.  The
production of LM naval frequency meters presumably also incorporated
this computer system.

An in-depth article about this system including photos, partial
schematics, integration formulae and much more can be found in the magazine
'Electronics'  for May, 1944 at page 98.  I was surprised that such
information would have been made public during the War, but evidently
it was decided that either the enemy already knew about this process by
1944 or else it was too late for them to make beneficial use of it.  
To the best of my knowledge, no other nation at the time produced a 
micrometer frequency meter with the accuracy or quality of the BC-221, 
a wonderful piece of equipment which seldom receives much attention 
from collectors compared to its radio companions.

Regards,
Geoff Fors WB6NVH
Monterey California

--

Regards,
Jerry Proc VE3FAB   [email protected]
Web:      www3.sympatico.ca/hrc/haida
HMCS HAIDA Historic Naval Ship, Toronto Ontario