Current Flowing Indicator.

[pwdrive]

Maybe back then 2 x pi x f was used to represent angular velocity rather than the small omega sign.
Anyone else got any thoughts?

Lawrence.

[Joe]

There's never an Alan around you need one.

- Joe

[Skywave]

. . . at one time wasn't ω used for ohms and Ω for megohms?
- Joe

"Ω for megohms" Ω was and is only ever used to symbolise 'ohms' - hence, kΩ and MΩ.
Incidentally, if you're ever looking at schematic diagrams that were drawn in the U.S.A., circa 1940, beware of their use of "MEG" where it is assigned to a resistor: they mean 1,000 by that term, NOT 1,000,000. The cct. diag. of the AR88D receiver is an illustrative example.

Al

[Skywave]

I first met the small omega sign many years ago when studying applied mathematics: used to symbolise angular rotation and also in relation to simple harmonic motion (SHM). Both forms of motion are of a regular periodicity: hence, 2*pi*f in electrics: the sine-wave is a graphical representation of SHM.

Al.

[Joe]

           

[Skywave]

Hi Joe - as I have mentioned before, I've been engaged in electronics and radio work since I was a youngster and over that time period, I have looked at all manner of cct. diags., but I have never seen the Greek symbol [lower case omega] ever used as a symbol for resistance - until now! Now if that symbol was in use in the 1920's - 1930's, that would explain it: my experience with kit from that era is very thin.

Ah! The value of membership of a radio / electronics forum - there's always something new to learn!

Further thought; ref. your cct. diags.: I see that on the first one, both the lower and upper case omega symbol is used; on the next two, only the lower case version is used. Idea: since very early wireless sets used wire-wound resistors, was the symbol [lower case omega] used to denote a wire-wound 'resistance' - as they were then called - as opposed to a carbon type - or perhaps vice-versa ?

Al.

[Joe]

"Out of the mouths of babes and sucklings" - I've only been doing it for eighteen months.

A good thing to look at would be original diagrams of Great War military radios. When I was looking last night I found a few but they'd been re-drawn.

- Joe

[pwdrive]

"Idea: since very early wireless sets used wire-wound resistors, was the symbol [lower case omega] used to denote a wire-wound 'resistance' - as they were then called - as opposed to a carbon type - or perhaps vice-versa ?"

Hi Al, that might make sense as the humdinger resistors shown in the 3rd diagram would definately be w.w. jobs.

Lawrence.

[Joe]

On the first diagram are two labelled "1Ω" and ".25Ω." Would they REALLY be that low?

- Joe

[pwdrive]

I doubt it Joe, I would guess 1 meg and 250k maybe, if that was the case then the large omega sign would equal 1 meg. Bit of a mystery.

Lawrence.