'ω' and 'Ω' versus 'Ω' and 'MΩ'

[Dave Moll]

I hope I haven't simply imagined this, but I feel sure it has been mentioned on this forum in the dim and distant past that there were once instances where 'ω' was used for ohms and 'Ω' used for megohms, but can anyone point to examples of this usage?

[Nuvistor]

I have not heard of that always thought lower case Omega was short hand for 2πf.
Apologies don’t have the Greek keyboard.

[AC/HL]

My 1927 Melody Maker has grid leaks marked 3Ω and 4Ω meaning Megohms. They're both O/C.

[Nymrod121]

I've not seen it either. I agree with Frank on use of lower-case ω as short form of 2πf.
Cheers
Guy

[Nuvistor]

Originally Posted by AC/HL

My 1927 Melody Maker has grid leaks marked 3Ω and 4Ω meaning Megohms. They're both O/C.

There you are, always something to learn.

[G6Tanuki]

Not come across that nomenclature before, but there have historically been some 'odd' conventions: for example the official 16-February-1943 schematic for my RCA AR-88D receiver uses "M" to indicate Kilohms, and "Meg" for Megohms.

Which leads to things like the grid-resistor for a 6V6 being marked "330M" which I at first read as meaning 330Megohms, and causing more than a few seconds of cognitive dissonance.

[M0FYA Andy]

I recollect seeing 'ω' used for ohms, but I'm not sure where...……….

[Herald1360]

You haven't imagined it- I have certainly mentioned it somewhere or other. I've seen it in 1920s publications though it may well date back well before then as a convention.

When first encountered without any context it can be rather confusing!,

ω is lower case omega, Ω is upper case.

[Refugee]

I have a feeling that 'ω' comes from measuring resistivity of metals in physics and was 1 over ohms.

[Herald1360]

1 over ohm was called a mho but now it's a Siemens. I don't recall it being symbolized by ω.

An upside down Ω was used, though, which is superficially similar.

[julie_m]

The use of lower-case ω to represent 2 * π * frequency (and thereafter working in radians as opposed to cycles) is fairly common in circuit analysis. When working with sine and cosine functions, you can use the more general form of Euler's identity

e ** j * x == cos(x) + j * sin(x)

Substituting x = j * ω * t in the exponential function gives us a function with the cosine in the real part and the sine in the imaginary part (so nicely a quarter of a cycle apart).

[Refugee]

I remember now it was in AC theory.

[Skywave]

I've seen 'ω' used for ohms in early American literature.

Al.

[steve102]

Some of the resistors in my Ultra 22 radio are labelled with the ω symbol which you can see in the attached pictures. Unfortunately, many of them were open circuit due to breakage of their brass end connectors.

Steve

[peter_scott]

I thought ω was always used to represent frequency.
ω = 2πf

Peter

[Silicon]

I think I have seen that symbol on an old multimeter that was made in europe.

[Gridiron]

This was common usage in the 1920's, I'm surprised more members don't know about it, maybe there's not much interest here in 20's radios. Examples are in resistors in early Marconi sets such as the V2, V3 ,etc, all marked in this way.
Mike.

[John10b]

My 1954 “Foundations of Wireless “ 5th edition, 1954, by Mr Scroggie shows lower case Omega as 2nf. Sorry can’t insert mathematical symbols, but you know what I mean.
Cheers
John

[terrykc]

Originally Posted by Nuvistor

Apologies don’t have the Greek keyboard.

Originally Posted by John10b

Sorry can’t insert mathematical symbols, but you know what I mean.

If you are using Windows, the free Character Map utility that come with it allows you to copy and paste any character you like into your posts.

Every time I need a new one, I copy it into a notepad file which contains every non-standard character that I've ever used - symbols, fractions, accented characters, etc.

If I'm using more than one non standard character, I just keep the Notepad file open on the desktop so I can quickly go back to it as required.

I've never come across a resistor or reference using ω for ohms but I do recall, as a schoolboy, when I first started dabbling with old radios being totally confused by all the capacitors marked in Mega Farads ...

[ColinTheAmpMan1]

When at university, I used to refer to the "ω" in ω=2πf with a shorter word - "bum", for what I thought was an obvious reason....
Colin.