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Author Topic: Yo................ Vincenzo.......................  (Read 177009 times)
AC5UP
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« Reply #240 on: February 23, 2013, 08:31:47 AM »

Years ago one of the Ham magazines did a write up on some of the more unusual items that Unca' Sam had on his big olive drab test bench. The BC-221 was one of them...  Not because of the design sophistication or exceptional parts quality, but because each meter had an extensive calibration procedure.

IIRC, each unit coming off the line was tuned to a long list of calibration frequencies.  The knob settings for each frequency was recorded on a typed reference card specific for that meter, possibly in duplicate.  The field operator would tune an unknown signal then compare the knob settings against the calibration card.  This was a very time consuming manufacturing process and given the large number of BC-221's on the surplus market the question became how-in-the-hell were they able to calibrate that many meters before the war ended?

It's one thing to crank out combat boots in quantity, but a boot doesn't need to be documented in detail........

I posted the URL as this particular example appears to have aged gracefully and thanks to the fungus proofing has historic provenance.  For all I know the cal card is also dated, but one glance tells you it's the real deal from 1944.  Which is why Vinnie wants it.   Tongue
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K8AXW
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« Reply #241 on: February 23, 2013, 09:25:35 AM »

5UP:  The BC-221 was indeed a sophisticated and well built piece of gear.  "We" had about 25 of time online at any one time and I always wondered about how these things were calibrated.  The interpolating guide book that each meter had was pretty thick and each one was different!

After using one for a few years and now 60 years later owning digital readout frequency counters with unbelievable accuracy, I have a new level of respect for how they did things back in the 'olden times.'

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G3RZP
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« Reply #242 on: February 23, 2013, 12:41:38 PM »

Apparently one manufacturer (GE?) produced an automated setup to calibrate BC221s. Not sure how it worked though.

Of course, all the modern 'but freaks'  (i.e. digital guys) will pooh pooh it, but for those who know how to use it, it's still an awesomely useful piece of gear - and will give answers modern kit cannot.
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N4NYY
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« Reply #243 on: February 23, 2013, 01:09:09 PM »

Got one of these at a local hamfest for $5 !

http://www.ebay.com/itm/General-Electric-GE-Sportmate-Radio-Repair-Parts-/380427080803?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D14%26meid%3D5804619934973419532%26pid%3D100015%26prg%3D1006%26rk%3D1%26sd%3D380427080803%26

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AC5UP
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« Reply #244 on: February 23, 2013, 05:36:28 PM »

Yeah, but has it been rust and fungus proofed?

If you open up the battery compartment to find mushrooms growing there, I'd say that's your answer................

In other news, I'm one of the lucky bastards who can say they own a BC-221. I also regret not having used it in many moon.  My Bad.  No doubt on long winter nights the metal tubes inside long for the warmth of a filament glow only they can see... But, just for grins & giggles, I surfed over to BAMA to download this bad boy:  http://bama.edebris.com/download/military/bc221/bc221.djvu

OMG !!!  The BC-221 really is a fine quality analogue signal generator with potential accuracy far in excess of lesser designs like the IGGY-42 you spent so much time.... Uhhhhh... How should I say... " Polishing A Turd " ...?  Live & Learn.  All I know is that someone with exquisite taste in electro-militaria collectables is going to find a home for that BC-221 and never regret it........ Or need to clean out 69 years worth of fungus inside.

 Wink
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G3RZP
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« Reply #245 on: February 24, 2013, 03:25:53 AM »

I've only got 3 BC221s.....
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AC5UP
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« Reply #246 on: February 24, 2013, 04:51:25 AM »


...that settles it!  I'm going to take up a collection at my local Hamfest next month to get a few more for you.

Apparently they're more appreciated in the UK than New Jersey.  And to think that Bendix built them in Baltimore....   Roll Eyes
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N4NYY
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« Reply #247 on: February 24, 2013, 06:31:51 AM »

I've only got 3 BC221s.....

That is just wrong! LOL
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G3RZP
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« Reply #248 on: February 24, 2013, 06:43:17 AM »

Only one has the calibration book and the case: it is fungus and moisture proofed. According to the frequency counter, it's still within its original specification on accuracy, once you set the 1 MHz crystal to frequency.

The others are naked chassis.


The main failure mode I have found is the crystal refusing to oscillate if there has been any of the paint come off where the clamp holds the crystal. A bit of scotch tape as an insulator fixes that, though.
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N4NYY
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« Reply #249 on: February 24, 2013, 06:54:31 AM »

Only one has the calibration book and the case: it is fungus and moisture proofed. According to the frequency counter, it's still within its original specification on accuracy, once you set the 1 MHz crystal to frequency.

The others are naked chassis.


The main failure mode I have found is the crystal refusing to oscillate if there has been any of the paint come off where the clamp holds the crystal. A bit of scotch tape as an insulator fixes that, though.

Have you ever tried that liquid electrical tape? Wondering if that would work.
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G3RZP
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« Reply #250 on: February 24, 2013, 10:28:01 AM »

>Have you ever tried that liquid electrical tape? Wondering if that would work.<

I'd have to BUY that! Do you think I'm MADE of money?
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N4NYY
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« Reply #251 on: February 24, 2013, 04:42:28 PM »

>Have you ever tried that liquid electrical tape? Wondering if that would work.<

I'd have to BUY that! Do you think I'm MADE of money?

You can do what I do and find everything for $5 !
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G3RZP
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« Reply #252 on: February 25, 2013, 01:24:35 AM »

$5! I said I'm not made of money!!
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AC5UP
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« Reply #253 on: February 25, 2013, 03:22:30 PM »

You have to remember that in New Jersey it's possible to buy certain goods at a significant discount........

They're usually described as having fallen off the back of a truck.

 Grin
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N4NYY
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« Reply #254 on: February 25, 2013, 03:42:07 PM »

It could be worse. If he was in Italy, $5 = 1,000,000 Lire. LOL
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