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10-12-2014, 05:24 PM
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#1
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Carl, nn5i
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
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One-question quiz #1
For many years, the Royal Navy bought all capacitors (for use in its radios) in jars. Why?
24 hour rule.
__________________
-- Carl
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10-12-2014, 06:01 PM
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#2
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Junior Member
Join Date: Jan 2014
Posts: 1
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One question quiz - capacitors
Because capacitors were made with cardboard. Moisture would cause the capacitance to change. The jar helped keep the moisture out.
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10-12-2014, 06:28 PM
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#3
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Administrator
Join Date: Nov 2007
Location: Fayetteville, GA, USA
Posts: 3,017
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Because the Minister of the Royal Navy, Admiral Winston Churchhill, had a cousin, the Earl of Worstershire, whose industrial empire manufactured glass jars. It was political. And delayed the development of the zip lock bag by 75 years.
The sailors then would make homemade rum and store the booze in the discarded jars. The radioman on a destroyer was nearly as popular as the cook.
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10-12-2014, 07:52 PM
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#4
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Carl, nn5i
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
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Ummm -- try again, guys.
__________________
-- Carl
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10-12-2014, 08:18 PM
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#5
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Administrator
Join Date: Nov 2007
Location: Fayetteville, GA, USA
Posts: 3,017
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And don't forget the 24 hour rule.
For those unfamiliar, serious responses are held back for 24 hours in order to allow all members to participate.
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10-12-2014, 10:07 PM
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#6
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Senior Member
Join Date: Jul 2013
Location: Douglasville, GA
Posts: 417
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Since I know the answer I will wait until 6:25pm Monday. Very clever Carl! They quit that purchasing method in the early 1950's.
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10-13-2014, 02:45 PM
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#7
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Carl, nn5i
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
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Quote:
Originally Posted by electricflyer
Since I know the answer I will wait until 6:25pm Monday. Very clever Carl! They quit that purchasing method in the early 1950's.
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And I'll hold off until you have posted.
__________________
-- Carl
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10-13-2014, 03:20 PM
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#8
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Administrator
Join Date: Nov 2007
Location: Fayetteville, GA, USA
Posts: 3,017
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Oh, the suspense!!
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10-14-2014, 06:37 AM
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#9
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Carl, nn5i
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
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Nowadays we buy capacitors in farads, μF, and pF. But in the early years of radio, capacitances were often stated in jars.
From the (British) Admiralty Handbook of Wireless Telegraphy, 1931:
The jar is the Service unit, and is very useful when dealing with the small capacities met with in ordinary wireless practice.
1 farad = nine hundred million jars
1 μF = 900 jars
Variable capacitors were difficult to make in the early 20th century, and transmitters were tuned by adding or removing fixed capacitors in parallel. Almost always, each of these capacitors was a Leyden jar and actually consisted of a thin-walled glass jar with metal (foil or plating) on the inside and outside surfaces. Operators would add or remove capacitance by hooking and unhooking connections to the jars, and often prepared tables listing how many Leyden jars to use for each operating frequency.
Soon the Leyden jars became more or less standardized, and a typical one had a capacitance of about 1111 pF. This value of capacitance came to be called a jar, and the Royal Navy used this as a standard unit until 1937, when it was made obsolescent in order to align Royal Navy practice with commercial practice. Some of the fleet may have used the jar as a unit of measurement as late as the early 1950s.
I believe, without being certain, that the US. Navy also specified capacitance in jars in the early 20th century.
__________________
-- Carl
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10-14-2014, 01:36 PM
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#10
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Senior Member
Join Date: Jul 2013
Location: Douglasville, GA
Posts: 417
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I completely forgot about the answer. I got busy fixing supper and didn't remember until I was in bed. Yep, the measurement of capacitors was in Jars instead of farads.
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10-14-2014, 02:02 PM
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#11
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Carl, nn5i
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
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Was supper something that came in jars?
__________________
-- Carl
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10-14-2014, 06:29 PM
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#12
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Administrator
Join Date: Nov 2007
Location: Fayetteville, GA, USA
Posts: 3,017
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I was going to guess (surmise, postulate) that the caps were placed in jars to avoid them creating a spark on board a vessel which carried a large supply of black power and other high explosives.
But then they ran them with coal or oil fired boilers, so what real difference would that have made?
Good question though, Carl.
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10-14-2014, 10:18 PM
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#13
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Senior Member
Join Date: Jul 2013
Location: Douglasville, GA
Posts: 417
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I'll have to confess, Google comes through in the tough ones.
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10-15-2014, 02:24 AM
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#14
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RV in 2016
Join Date: Apr 2014
Location: Patterson, CA (CA central Valley east of SF)
Posts: 92
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Well I ran this through my gray matter for 48 hours and barely resisted the temptation of Google.
Never would have guessed Leyden jars. Never. Like others above I was thing jars as packing containers for safety, sparks, humidity, shelf life, and on and on. None of it seemed right though and without EVER seeing any NOS on eBay for capacitors packed in jars in "Naval minty" condition , I knew I was running in the wrong circle.
Unit of measure. Approximately a nanofarad. Whoda thunk it ? Great quiz question, Carl.
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73,
Bill - W7JZE
"Dar" - XYL
(And our little Bichon Frisé "Sparkle")
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10-15-2014, 07:15 AM
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#15
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Senior Blame Catcher
Join Date: May 2010
Location: Oakland City Ind.
Posts: 265
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Lends a whole new meaning to the term "JAR HEAD", no slam intended .
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DE: John W9WLS
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