The future: DC mains

[wrights...]

They are very inefficient.

Bill

[wrights...]

Some tellys had the biscuits arranged so the most likely combinations of the two channels in use were adjacent. So the sequence would be something like 1, 9, 4, 8, 3, 11, 2, 10 and so on.

Bill

[Paul]

You can see that a *lot* of science went into this :-/

Competing business interests designed the electric chair, as a means to influence how electrification of the countryside would be performed. Using AC for electrocution was intended to make Westinghouse look bad. That's why some of the parties went about acquiring Westinghouse branded generators as a means of making Westinghouse look bad.

"George Westinghouse later commented that, "They would have done better using an axe",[33] and a witnessing reporter claimed that it was "an awful spectacle, far worse than hanging". "

It makes the antiaircraft gun look like a humane solution.

Paul

[Rod Speed]

They stole that from the british.

[Paul]

GPS modules have a very accurate 1PPS pulse output, and if you want to measure like that, you can. You can measure the period of a day, to 100 nanosecond accuracy, sufficient for slicing off a 50Hz cycle as you see fit. Connect the 1PPS output to a 86400 counter, use that to snapshot your mains counter.

You can also connect a mains based transformer, to your PC sound card and record a "whole day of humming" :-) The only problem with that, is drift of the sampling clock used on the PC. And not knowing exactly which clock in the PC controlled the sampling.

Since the sound card is stereo, the other channel could be used to record the 1PPS signal from the GPS. You will not get a faithful reproduction of the square wave, but the waveform should still be suited to time measurements. Don't forget to attenuate the input signals to stay within the 1VRMS input levels on LineIn.

Paul

[Joe]

Whereas the switch needs to be designed to quench arcing, while AC arcs tend to extinguish a hundred times a second and then need to re-strike if they are to continue.

Swings and roundabouts.

But changing the system over will cost a bob or two... do you think electricity prices are high now? The people who pay will never get any say in a decision.

[Joe]

Even today the mains frequency gets pulled down a bit during the day, and things are speeded up a little at night to restore an average 50Hz.

A few of us learned at school (not from the teachers) how to restart some mains electric clocks so they ran backwards. In some places there was a master clock and individual clocks were driven by pulses from the master, and could only go forwards.

[The Natural Philosopher]

It is still true today. Average is always exactly 50Hz over a long period.

[Harry Bloomfield Esq]

Yes, I know, but this was in the pre-GPS days.

[Harry Bloomfield Esq]

True, but slightly more efficient than the alternative and also the only way they can work on 12v DC/ gas or mains.

[Harry Bloomfield Esq]

I wonder why they had so many positions, when there was only a choice of one or other - BBC or ITV?

[wrights...]

Compressor fridges are available that will work on 12 or 24V. You can't run a gas fridge on a yacht because of the instability of the vessel.

Bill

[wrights...]

Bill

[Fredxx]

That's not so clear-cut. Single phase I would agree, but 3-phase, or multiphase gets close in terms of copper losses and required insulation. Or so I was taught but struggling to find links to the same theory.

Corrosion is an issue with DC cables, where the polarity is swapped on a regular basis.

[Peter Able]

Only one tuner assembly (and bezel) required throughout the UK. Also that in the 50s and 60s, there was more use of the term Channel 9 than ITV - etc...

In the later 50s, you'd come across external convertor boxes, frequency-changing Band III (i.e. ITV) down to Band I. Sounds a bit bizarre, but TVs were expensive. I remember my father paying, in 1955,

67 guineas for a 14" Ekco TV. That is, according to RPI, the equivalent of £2,200 in 2022. So people used all sorts of add-ons to not have to abandon a TV (booster transformers, regunned CRTs, dropper sections etc. etc.)

PA

[Peter Able]

Err, what?

[Colin Bignell]

They work fine on canal boats.

[Bob Eager]

My school had such a system, with pulses every 30 seconds. The master clock was a beautiful thing, in a long wooden case with a brass pendulum and all the working parks visible.

That system is long gone, but I visited recently and they have kept that clock in the same place (the main entrance hall for visitors). It looks very nice.

[Bob Eager]

We could get ITV from at least two different places, and where I am now there has been a choice of three for many years.

And it allowed for future expansion. It was easy enough to add BBC2.

[SH]

and where I am, I can get 4 different BBC1 regions and 4 different ITV 1 regions..... plus all the other regions on Freesat.