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#1
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Odd resistors identification
Some of the schematic diagrams of war times radios - though not all of them -
adopt an odd way of identifying resistance values. For instance a 200.000 ohm resistor is marked "200 Mohm". The "M" means kilo, not mega! Conversely a 2.000.000 ohm resistor is marked "2 Megaohm". Does any one know the origin of this way of marking resistors and when it was abandoned? 73 Tony I0JX Rome. Italy |
#2
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Odd resistors identification
In "Antonio Vernucci"
wrote: Does any one know the origin of this way of marking resistors and when it was abandoned? It was based on the Roman numeral "M" representing 1,000, but I don't know when it stopped being used. I still see "M" being used to represent thousands of dollars, and MCF is still a pretty standard representation of "thousand cubic feet" of natural gas. -- Bert Hyman W0RSB St. Paul, MN |
#3
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Odd resistors identification
It was based on the Roman numeral "M" representing 1,000, but I don't
know when it stopped being used. Living in Rome, I should have known... hi. I have a diagram dated 1953 in which M still represents 1000. In that diagram they use MF for microfarad (on the other hand a thousand farad would not make sense). I still see "M" being used to represent thousands of dollars, and MCF is still a pretty standard representation of "thousand cubic feet" of natural gas. Good to know, I would not have suspected that M$ could mean just a thousand dollars and not a million dollars. We here commonly use MEuro for million Euro. Thanks & 73 Tony I0JX |
#4
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Odd resistors identification
Edmund H. Ramm wrote:
In "Antonio Vernucci" writes: [...] I have a diagram dated 1953 in which M still represents 1000. In that diagram they use MF for microfarad [...] There are also diagrams where m (milli, 10^-3) is used to represent mikro (10^-6). Even worse and confusing are those, where mmF gets used when pF (pico, 10^-12) is meant. Huh? What's confusing about micro-micro farads? :-):-) -- Robert (Bob) Smits, VE7HS & Linux Fan |
#5
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Odd resistors identification
"Bob Smits" ha scritto nel messaggio
news:HbmdncivItyZOM7RnZ2dnUVZ_uqdnZ2d@islandhostin g.com... Edmund H. Ramm wrote: In "Antonio Vernucci" writes: [...] I have a diagram dated 1953 in which M still represents 1000. In that diagram they use MF for microfarad [...] There are also diagrams where m (milli, 10^-3) is used to represent mikro (10^-6). Even worse and confusing are those, where mmF gets used when pF (pico, 10^-12) is meant. Huh? What's confusing about micro-micro farads? :-):-) -- Robert (Bob) Smits, VE7HS & Linux Fan Among the odd markings: - in the 60ies it was fairly common to use kpF (kilopicofarad) to mean nF (nanofarad) - in the 30ies, German power mica capacitors were marked in centimeters (cm). 1 cm is equal to about 1.1 pF 73 Tony I0JX |
#6
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Odd resistors identification
"Antonio Vernucci" wrote in message ... "Bob Smits" ha scritto nel messaggio news:HbmdncivItyZOM7RnZ2dnUVZ_uqdnZ2d@islandhostin g.com... Edmund H. Ramm wrote: In "Antonio Vernucci" writes: [...] I have a diagram dated 1953 in which M still represents 1000. In that diagram they use MF for microfarad [...] There are also diagrams where m (milli, 10^-3) is used to represent mikro (10^-6). Even worse and confusing are those, where mmF gets used when pF (pico, 10^-12) is meant. Huh? What's confusing about micro-micro farads? :-):-) -- Robert (Bob) Smits, VE7HS & Linux Fan Among the odd markings: - in the 60ies it was fairly common to use kpF (kilopicofarad) to mean nF (nanofarad) - in the 30ies, German power mica capacitors were marked in centimeters (cm). 1 cm is equal to about 1.1 pF 73 Tony I0JX and cps instead of Hertz Ah...those were the good ol' days |
#7
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Odd resistors identification
- in the 60ies it was fairly common to use kpF (kilopicofarad) to mean nF
(nanofarad) Never saw that before. it was not just on the doagrams. I have some capacitors marked that way... 73 Tony I0JX |
#8
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Odd resistors identification
Well, "m" is reserved for "milli". Using a QWERTY typewriter (remember
them?) or ASCII computer keyboard IMO "u" is the better substitute for "micron". But "p" and "n" are on all those keyboards. So there was/is no need for the above "mmF" construct, or awkward notations like .005uF when 5nF would say it much nicer. 73, Eddi ._._. -- Yes, but for some reason 5nF was not of common use before about 25 years ago. ..005uF or 5kpF was the standard, who knows why.. Tony I0JX |
#9
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Odd resistors identification
In message , olfart
writes "Antonio Vernucci" wrote in message t... "Bob Smits" ha scritto nel messaggio news:HbmdncivItyZOM7RnZ2dnUVZ_uqdnZ2d@islandhostin g.com... Edmund H. Ramm wrote: In "Antonio Vernucci" writes: [...] I have a diagram dated 1953 in which M still represents 1000. In that diagram they use MF for microfarad [...] There are also diagrams where m (milli, 10^-3) is used to represent mikro (10^-6). Even worse and confusing are those, where mmF gets used when pF (pico, 10^-12) is meant. Huh? What's confusing about micro-micro farads? :-):-) -- Robert (Bob) Smits, VE7HS & Linux Fan Among the odd markings: - in the 60ies it was fairly common to use kpF (kilopicofarad) to mean nF (nanofarad) - in the 30ies, German power mica capacitors were marked in centimeters (cm). 1 cm is equal to about 1.1 pF 73 Tony I0JX and cps instead of Hertz Ah...those were the good ol' days But cps and c/s are still valid and understandable units of frequency. If I recall correctly, when it was first proposed that we use the 'continental' Hertz, the Hz was supposed to be only for electrical units. Therefore, the electrical drive to a loudspeaker would be in Hz, but the movement of the cone would be in c/s. -- Ian |
#10
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Odd resistors identification
In message , Antonio
Vernucci writes Well, "m" is reserved for "milli". Using a QWERTY typewriter (remember them?) or ASCII computer keyboard IMO "u" is the better substitute for "micron". But "p" and "n" are on all those keyboards. So there was/is no need for the above "mmF" construct, or awkward notations like .005uF when 5nF would say it much nicer. 73, Eddi ._._. -- Yes, but for some reason 5nF was not of common use before about 25 years ago. .005uF or 5kpF was the standard, who knows why.. For some reason, Americans find the British use of 'puff' and 'puffs' (the colloquial 'pronunciation' of 'pF') highly amusing! -- Ian |
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