[ARC5] Unusual BC-221

[Bill Cromwell]

Hi Bill,

I can't speak to the new-in-sealed-box part of your question. The 'book' 
for each was produced by actually operating the individual units so I 
suspect they had to be "on-frequency" at the time they were boxed/shipped.

I have two LMs and have had my hands on a few others that passed through 
here on the way to other hams. My calibration has evolved to using one 
of two computer sound card DSP  programs and WWV. I set up my sound card 
program and radio so I can hear and display the WWV carrier - not at 
zero cps on the sprectrum but usually near 1 kc. The exact tone matters 
not. The xtal marker from an LM (or other source) is brought into play. 
Tweaking the xtal onto WWV will show the pip for the xtal creeping onto 
WWV's carrier and then a moire pattern will be seen advancing up the 
slope to WWV's peak. When it reaches that peak - "on frequency" the 
moire pattern will stop crawling and stop "wriggling". Never mind about 
calibration of the receiver, the sound card, or anything else. If any of 
that moves WWV will move with it and will will still be the "target".

The LMs I have had were all of unknown provenance. There is no way to 
know how much handling, shipping, bumping around may have happened. No 
way to know how many times calibrated, by whom, nor when. One of the two 
I have was DEAD on the first time I checked it with my spectrum display 
against WWV. The other one was in the moire on the low side slope - not 
detectable by ear. Only one of the LMs that came here for 'checkout' was 
ever any further than being in that moire pattern on one slope or the 
other. i suspect the one that was off was visited by somebody's "golden 
screwdriver" and it adjusted right back on the nose.

After all these years a good LM (or 221) is hard to beat.  They do 
tricks a digital frequency counter can't. But I suspect everybody on the 
list already knows that.

73,

Bill  KU8H



On 03/04/2015 02:35 AM, Fuqua, Bill L wrote:
>    Now, I have a question. There is an experiment I always wanted to try if I ever found a still boxed Bc221 or LM.
> Is it still accurate? Can you check it WWV perhaps or a well calibrated crystal calibrator to see if it still agrees with the book?
> First, how close is the crystal calibrator before making any adjustments to it, and then after setting the crystal calibrator
> how closely does the book match. I had always been amazed by the precision of many instruments made during WWII.
> 73
> Bill wa4lav
>
>