Power Frequency

From: Geoff Roberts <geoffrob_at_stmarks.pp.catholic.edu.au>
Date: Sat Apr 17 14:56:38 1999

----- Original Message -----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Sent: Sunday, April 18, 1999 3:27 AM
Subject: Re: Power Frequency


> We had strange mains voltages and freqeuncies until the 1950's/1960's.
> IIRC the last 100Hz (!) generator in England was at Lynmouth, and it
> lasted until the serious floods there in 1952 (?). The mains voltage in
> England, even for a 50Hz AC supply, could vary between 200V and 250V
> depending on the area that you lived in, and multi-tapped transformer
> primaries were common. I think we even had DC mains until that sort of
> date as well (judging from the number of 1950's radios and TVs with
> settings for DC mains).

The only non-standard mains freq I can recall was in Broken Hill. NSW.
The huge mines there generated their own power, (it's a little isolated, 300
miles from ANYwhere) and they ran the employees homes in the south of the
town off that for many years, it was supplied free to mine employees.
When the town got it's own generating capacity most of the non mine houses
switched to that. The nonstandard bit was that the mine power was 40 hz,
not by choice, but because an engineer screwed up the calculations and
ordered the wrong hardware (not sure what, possibly transformers IIRC).
Result was town power, 240 50hz but you paid for it (Diesel Gensets, not
cheap) or mine power, 240v 40hz, but free of charge, but which drove TV's
record players and electric clocks slightly whacky. Some people went to the
expense of having specially modded motors put into their turntables!
The practice finally ceased in the 80's when commercial power from the state
grid finally reached the region and the Galena St and Mine power stations
were decommissioned.

> > US NTSC is 525 line 60hz PAL 625 line 50hz. We use PAL. (There are
all
> > kinds of wierd variations, including a version of PAL with a 60hz field
rate
> > in South America somewhere - Brazil I think)
>
> Indeed. It's PAL-M (525 line, 60Hz vertical, 3.5...MHz subcarrier).
> There's also PAL-N (South Africa?) with 625 lines, 50Hz vertical, and
> 3.5... MHz subcarrier.

S/C 3.58Mhz like the NTSC stuff I imagine.

All our broadcast transmission stuff is PAL-D, with PAL-S compatibility,
625/50 4.43Mhz s/carrier.
Our Channel spacing is different (5.5Mhz) and so are our freq allocations.
For instance we still have TV channels in what is entirely an FM broadcast
band elsewhere. Causes probs for people who buy VCR's in Singapore only to
discover they can't pick up our local commercial station. (Ch4 is 100.7
audio, 95.? Video)

I have a couple of Apple IIc colour monitors that are NTSC, only work with
the computers, might be handy if I ever have to play an NTSC tape. (If I
had a NTSC VCR to do it with that is)

Cheers
Geoff Roberts
Received on Sat Apr 17 1999 - 14:56:38 BST

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