The future: DC mains

[Graham.]

I love the Tesla irony, but this is a non-starter isn't it?

https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc

--
Graham.
%Profound_observation%

[zall]

On Tue, 20 Sep 2022 07:45:51 +1000, Graham. <graham...@mail.com> wrote:

>
> I love the Tesla irony, but this is a non-starter isn't it?
>
> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc

No, it is feasible, tho not necessarily the best approach.

[Fredxx]

On 19/09/2022 22:45, Graham. wrote:
>
> I love the Tesla irony, but this is a non-starter isn't it?
>
> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc

It's been written by someone who doesn't seem to understand why we have
AC into homes and thinks DC is all you need to charge a Tesla car
battery. They don't seem capable of understanding Volts and Amps and
that these need to be tailored to charge a battery.

With the advent of power electronics, 50/60Hz transformers could perhaps
become redundant. The dielectric loss with burying AC cables is
significant such that DC may also become the choice of underground power
transmission within the UK.

[Cursitor Doom]

You're probably correct, but I hope I don't see it in my lifetime. As
someone who's a bit careless and tends to get electrified more
frequently than I would like, I find DC pretty scary. Nasty, zappy,
unforgiving stuff it is.

[Fredxx]

I'm surprised at your fear. The war of the currents was specifically
because AC was more dangerous but more practical for transmission:
https://en.wikipedia.org/wiki/War_of_the_currents

[John Bryan]

In message <op.1srjb...@pvr2.lan>

Typical small world thinking, they have never been near any sort of
manufacturing plant that use large motors.

--
John Bryan

[Colin Bignell]

On 19/09/2022 22:45, Graham. wrote:
>

> I love the Tesla irony, but this is a non-starter isn't it?
>
> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc
>

It is an argument that raged at the start of the last century. However,
when we developed a national grid, AC was chosen because of its
advantages for long distance transmission. The exception being undersea
cables, where dialectic loss is significant. However, the National Grid
uses overhead lines for most HV transmission.


--
Colin Bignell

[Fredxx]

Very large motors used in rolling mills were often DC. Converting 3
phase into DC is pretty easy. It's been done for railways for a very
long time.

The advantage of AC is the ability to change voltage for transmission,
and then back down again for local use.

[Cursitor Doom]

You would not be so surprised if you had an unusually high skin
resistance as I have. That makes AC the 'shock of choice' so to speak,
for me. The downside however - there's *always* a downside - is I get
zapped to hell and back in the Winter by static. Plus I blow senstive
electronics to kingdom come at that time of year, too. You can't win
either way.

[NY]

Why does having a high skin resistance make an AC shock better or worse
than a DC one, if you equate RMS for AC with DC value?

I've never had a DC shock, because the largest battery I've ever
encountered is a 12 V car battery, and the centre pin on a 20 V laptop
charger is usually shrouded. though I've had a few AC ones due to my own
stupidity.

On one occasion, many years ago, I'd turned an appliance off at its
internal double-pole switch, which made most of it perfectly safe -
until I happened to touch the live and neutral terminals on the switch
where the mains cable connects to the switch. I still have a pair of
"snake-fang" scars on the knuckle of one finger.

The other shock was something that only happens with modern Philips Hue
bulbs which can be turned off internally (eg using a smartphone app)
while mains power continues to be applied. I'd been changing all the
GU10 light fittings in the bedroom ceiling. I'd been very good, turning
off both the wall switch and the lighting-circuit MCB in the fuse box.
Then my wife asked me to change a couple more. The bulbs were off, so
the supply to the fittings was off. I didn't need to turn the switch off
at the wall. Not true! I found out as I went to unscrew the fitting from
the terminal block that connected it to the lighting circuit. That shock
was the mildest of all, probably because the RCD tripped within its
stated 30 msec.

I had a surprisingly strong shock off the TV aerial cable which was
plugged into my old telly. I'd had the cable plugged into a USB tuner
which was connected to my earthed PC, so the metal aerial plug was
earthed - until I unplugged the cable with one hand while holding the
metal PC case with the other. That was a nasty tingle. I spent a while
trying to identify the source, because the aerial cable was plugged into
the TV which in turn was connected by audio cables to the VCR and my
hi-fi system. Which was the culprit? It turned out to be the TV which
was applying about 150 V between aerial earth and mains earth, as
measured by a high-impedance multimeter, although via a high resistance.
With a resistor to simulate my arm-to-arm body resistance of about 100 k
ohms, the voltage dropped to about 80 V - much less dangerous, but still
enough to be felt, and enough to make me not want to repeat the
experience to measure the on-load voltage for real, hence the resistor
to simulate my body.

I knew a woman at university who could feel voltages as low as 1.5 V by
touching the two terminals with finger and thumb. She said she could
pick up batteries one by one from a pile, and sort the charged ones from
the flat ones by touch. Most of us have to test with out tongues to feel
voltages that low.

[John Rumm]

For high power transmission (>= 1GW) ISTR the cost crossover point is
something like 430 miles. The DC system has less parasitic losses on the
wire (and needs fewer of them since it's not 3 phase), but the
conversion gear is massively more expensive than a transformer.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

[zall]

I didn't read the original and stupidly assumed that they were
talking about the main long distance grid, not what is used at
the consumer level.

[Brian Gaff]

Well, back in the day of course we had both in different parts of the
country. The drawbacks with DC were corrosion, variable voltages and no way
to send over long distances as you could not use a transformer on DC.
Obviously a lot of these things can be designed around nowadays, but why not
simply go to 400hz AC as they use on some military equipment. The
transformers are more efficient, after all look at the tiny ones inswitch
mode power supplies.
In the end though, there simply is too much investment in AC. Assuming we
want to move power over very long distances and can design the kit to
convert it, I believe DC does have some advantages, but are they really
enough to make it worthwhile doing?
Brian

--

--:
This newsgroup posting comes to you directly from...
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Blind user, so no pictures please
Note this Signature is meaningless.!
"Graham." <graham...@mail.com> wrote in message
news:3iohih5k2tln49qg8...@4ax.com...

[The Natural Philosopher]

On 20/09/2022 00:05, Colin Bignell wrote:
> when we developed a national grid, AC was chosen because of its
> advantages for long distance transmission. The exception being undersea
> cables, where dialectic loss is significant. However, the National Grid
> uses overhead lines for most HV transmission.

Mostly wrong. AC allows easy voltage conversion so that long overhead
cables can be high voltage, and so use less aluminium and steel. It
could have as easily been high voltage DC if they had had semiconductor
technology capable of transforming it.

Undersea cable are usually DC not because of dielectric losses, but
because of *resistive* losses incurred by the cable capacitance
necessitating large out of phase currents that deliver no useful power,
just heat up the cable cores.

In short what you want for transmission is high voltage. The AC- or DC-
ness is purely a pragmatic way to get costs down, depending on the
technology available and its cost.

A further issue with AC is that in a network of multiple parallel paths
- like a continental grid - power via pone route may arrive out of phase
with anther route, due to path length differences. This again looks like
'out of phase' current and just heats up the wires.

--
When plunder becomes a way of life for a group of men in a society, over
the course of time they create for themselves a legal system that
authorizes it and a moral code that glorifies it.

Frédéric Bastiat

[jon]

On Mon, 19 Sep 2022 22:45:51 +0100, Graham. wrote:

> I love the Tesla irony, but this is a non-starter isn't it?
>
> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-
the-uk-s-power-distribution-from-ac-over-to-dc

I grew up with DC Mains and with all my early electrical experiments I
used rotary transformers. I obtained a variety of ex-gov/military bits and
pieces and was able to convert mains voltage 250v to 28vDC, 12vDC and
400vDC.

[Peeler]

"Who or What is Rod Speed?

Rod Speed is an entirely modern phenomenon. Essentially, Rod Speed
is an insecure and worthless individual who has discovered he can
enhance his own self-esteem in his own eyes by playing "the big, hard
man" on the InterNet."

https://www.pcreview.co.uk/threads/rod-speed-faq.2973853/

--
David Plowman about senile Rodent Speed's trolling:
"Wodney is doing a lot of morphing these days. Must be even more desperate
than usual for attention."
MID: <59a60da...@davenoise.co.uk>

[Peeler]

On Tue, 20 Sep 2022 12:27:45 +1000, zall, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>

--
Kerr-Mudd,John addressing the auto-contradicting senile cretin:
"Auto-contradictor Rod is back! (in the KF)"
MID: <XnsA97071CF43...@85.214.115.223>

[Fredxx]

On 20/09/2022 07:58, Tim Streater wrote:

> On 20 Sep 2022 at 01:09:35 BST, NY <m...@privacy.net> wrote:
>
>> On 20/09/2022 00:37, Cursitor Doom wrote:
>>> On Mon, 19 Sep 2022 23:44:23 +0100, Fredxx <fre...@spam.uk> wrote:
>>>> I'm surprised at your fear. The war of the currents was specifically
>>>> because AC was more dangerous but more practical for transmission:
>>>> https://en.wikipedia.org/wiki/War_of_the_currents
>>>
>>> You would not be so surprised if you had an unusually high skin
>>> resistance as I have. That makes AC the 'shock of choice' so to speak,
>>> for me. The downside however - there's *always* a downside - is I get
>>> zapped to hell and back in the Winter by static. Plus I blow senstive
>>> electronics to kingdom come at that time of year, too. You can't win
>>> either way.
>>
>> Why does having a high skin resistance make an AC shock better or worse
>> than a DC one, if you equate RMS for AC with DC value?
>>
>> I've never had a DC shock, because the largest battery I've ever
>> encountered is a 12 V car battery, and the centre pin on a 20 V laptop
>> charger is usually shrouded. though I've had a few AC ones due to my own
>> stupidity.
>

> The point about DC is that you can't let go, if you inadvertently grasp a live
> wire. With AC you can.

It is said the opposite is true, With DC you get a single shock, and
single muscle contraction. With AC your muscles contract 100 times a
second.

It is also said that AC is 5x more likely to lead to death but I don't
know how that is determined in terms of volts AC/DC/rms/peak etc.

[charles]

> know how that is determined in terms of volts AC/DC/rms/peak etc.Elec

Electric chairs ran/run off AC. It';s obviously more dangerous.

--
from KT24 in Surrey, England - sent from my RISC OS 4té
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

[Martin Brown]

On 19/09/2022 23:02, Fredxx wrote:

> On 19/09/2022 22:45, Graham. wrote:
>>
>> I love the Tesla irony, but this is a non-starter isn't it?
>>
>> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc
>>
>
> It's been written by someone who doesn't seem to understand why we have
> AC into homes and thinks DC is all you need to charge a Tesla car
> battery. They don't seem capable of understanding Volts and Amps and
> that these need to be tailored to charge a battery.

I agree it seems to have been written by someone clueless.

> With the advent of power electronics, 50/60Hz transformers could perhaps
> become redundant. The dielectric loss with burying AC cables is
> significant such that DC may also become the choice of underground power
> transmission within the UK.

Japan has an interesting and long standing DC grid interconnect.

This is because Tokyo adopted German AEG kit on 50Hz (and then later UK
kit) whilst Osaka installed USA GE kit on 60Hz. Accordingly all their
domestic appliances have to run on either frequency.

https://www.quora.com/Why-does-Japan-still-use-50Hz-and-60Hz-in-their-electrical-system

Unfortunately the DC interconnects were not able to move enough power to
the 50Hz grid after Fukoshima went down so it all got a bit messy.

International DC interconnects at high voltage may become more common
for undersea and underground cables for the reasons that you give. I
can't see them ever replacing the supergrid pylons any time soon though.


--
Regards,
Martin Brown

[Joe]

Another point is the use of AC between countries is difficult because
synchronisation of the countries' frequency and phase are required at
the point of interconnection. In Europe, this would require all
countries to be synchronised to France, because otherwise the French
would pick up their marbles and go home.

Given the distances, no loop could be formed, the continental grid
would need to be a tree. Over thousands of miles, even 50Hz phase
differences become significant.

And picking one make of car ("It is an irony and an anachronism that our
AC (alternating current) grid power distribution, first championed by
Nicola Tesla over 130 years ago is completely unsuited to the job of
charging Elon Musk's eponymous Tesla motor car!") to standardise DC
distribution to the home is beyond ludicrous.

"...100 times a second huffing and puffing of AC power into the strong
steady flow of DC, which is what batteries crave." Honestly.

--
Joe

[Clive Arthur]

On 20/09/2022 09:48, Fredxx wrote:
> On 20/09/2022 07:58, Tim Streater wrote:

<snip>

>> The point about DC is that you can't let go, if you inadvertently
>> grasp a live
>> wire. With AC you can.
>
> It is said the opposite is true, With DC you get a single shock, and
> single muscle contraction. With AC your muscles contract 100 times a
> second.

Increase the frequency and you won't get a shock.

--
Cheers
Clive

[Fredxx]

Yes. I can also remember the burn after getting too close to the top cap
of a line-output valve. That would have been 15.625kHz.

[Scott]

When was your place converted to AC (if you were still there, that
is)? I think our house was originally wired for DC as some of the old
switches were extremely heavy duty and fitted with springs. I was
told this was to prevent arcing.

As a matter of interest, were any appliances unavailable? I assume
lighting was interchangeable (as long as not fluorescent). Radiators
would be okay. Ditto cookers and electric kettles. I believe radios
were made AC/DC. Could a fridge be run on DC? Were DC televisions
made?

Were red and black colours used? Was one terminal positive and the
other neutral, or was the other terminal negative (eg +120V / - 120V)?
Was an earth used in DC systems?

Was it possible to have an electric clock in the absence of a mains
frequency?

I have tried to research on Google but there seems to be remarkably
little detail.

[Bob Eager]

On Tue, 20 Sep 2022 13:30:30 +0100, Scott wrote:

> On Tue, 20 Sep 2022 07:22:08 -0000 (UTC), jon <j...@nospam.cn> wrote:
>>I grew up with DC Mains and with all my early electrical experiments I
>>used rotary transformers. I obtained a variety of ex-gov/military bits
>>and pieces and was able to convert mains voltage 250v to 28vDC, 12vDC
>>and 400vDC.

I did too, for a little while. I lived in Brighton.

> When was your place converted to AC (if you were still there, that is)?

Aroundf 1958-59.

> I think our house was originally wired for DC as some of the old
> switches were extremely heavy duty and fitted with springs. I was told
> this was to prevent arcing.

Indeed. The 15 amp sockets had foot operated switches. I once pulled out
the plug for the electric fire, while it was on. My father had left a
newspaper next to it. I enjoyed seeing the fire engine. No serious damage.

> As a matter of interest, were any appliances unavailable? I assume
> lighting was interchangeable (as long as not fluorescent).

Lighting was OK; we did get fluorescent not long after (my father worked
for the electricity board).

> Radiators would be okay. Ditto cookers and electric kettles.

Yes, all of those.

> I believe radios were made AC/DC.

Yes, they had a rectifier and a dropper resistor.

> Could a fridge be run on DC?

Yes, fridges were fine. We had one long before the change.

> Were DC televisions made?

Yes, see radios above.

> Were red and black colours used?

Yes.

> Was one terminal positive and the other neutral

Yes

> Was an earth used in DC systems?

Yes. 3 pin plugs (well, and 2 pin ones for small stuff).

> Was it possible to have an electric clock in the absence of a mains
> frequency?

We never had one.


--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

[Joe]

On Tue, 20 Sep 2022 13:30:30 +0100
Scott <newsg...@gefion.myzen.co.uk> wrote:


> Were DC televisions
> made?
>

Yes, TVs of the Fifties were all AC/DC, with mains droppers (big
resistors) to get appropriate voltages. This was my parents' first TV,
bought around 1957:

https://www.radiomuseum.org/r/ferguson_306t.html
https://www.vintage-radio.net/forum/attachment.php?s=bb23081888735c55e30c8be5e7442b9a&attachmentid=201452&d=1584945915

It was definitely AC/DC. Six external controls plus the tuner, needing
vertical or horizontal hold adjustment every ten minutes or so.

> Was it possible to have an electric clock in the absence of a mains
> frequency?

Not an accurate one, at least not without being rack-mounted and hugely
expensive. It wasn't until transistors were widely available that
affordable accurate clocks could be made without AC mains.

--
Joe

[N_Cook]

On 19/09/2022 22:45, Graham. wrote:
>
> I love the Tesla irony, but this is a non-starter isn't it?
>
> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc
>

Southampton central power station was about the last UK plant to supply
DC to nearby homes as late as mid 1960 IIRC.
The deep-drilling and geothermal plant was built on the site, curiously.
Oddly the underwater interconnectors between European coutries tend to
be very high DC


--
Global sea level rise to 2100 from curve-fitted existing altimetry data
<http://diverse.4mg.com/slr.htm>

[Andy Burns]

Joe wrote:

> Another point is the use of AC between countries is difficult because
> synchronisation of the countries' frequency and phase are required at
> the point of interconnection. In Europe, this would require all
> countries to be synchronised to France, because otherwise the French
> would pick up their marbles and go home.

I think every connection (that doesn't go underwater) is all one big
pan-european system

<https://entsoe.eu/data/map>

A few years ago Kosovo/Serbia were dragging the whole frequency down by taking
more load than the generation they were providing?

There was reference to ukraine chopping itself off from the russian grid and
joining the european grid, but the map doesn't seem to reflect that.

[Jeff Layman]

On 19/09/2022 22:45, Graham. wrote:
>
> I love the Tesla irony, but this is a non-starter isn't it?
>
> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc

GreenLibDems, eh? Some of the greatest minds in the land of make believe...
<https://www.youtube.com/watch?v=mQpzwR7wLeo>

--

Jeff

[Fredxx]

On 20/09/2022 14:18, N_Cook wrote:
> On 19/09/2022 22:45, Graham. wrote:
>>
>> I love the Tesla irony, but this is a non-starter isn't it?
>>
>> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc
>>
>
> Southampton central power station was about the last UK plant to supply
> DC to nearby homes as late as mid 1960 IIRC.
> The deep-drilling and geothermal plant was built on the site, curiously.
> Oddly the underwater interconnectors between European coutries tend to
> be very high DC

Hardly 'oddly'. The UK and European mains networks are asynchronous, so
cannot be directly connected. Dielectric loss is significant in salt
water, so DC is preferred on two counts.

[Scott]

On Tue, 20 Sep 2022 09:48:34 +0100, Fredxx <fre...@spam.uk> wrote:
[snip]

>>
>> The point about DC is that you can't let go, if you inadvertently grasp a live
>> wire. With AC you can.
>
>It is said the opposite is true, With DC you get a single shock, and
>single muscle contraction. With AC your muscles contract 100 times a
>second.

This was my understanding too, that DC would throw you across the room
but AC would paralyse the muscles and stick you to the conductor.

>
>It is also said that AC is 5x more likely to lead to death but I don't
>know how that is determined in terms of volts AC/DC/rms/peak etc.
>

For the above reason, I assume?

[jon]

On Tue, 20 Sep 2022 13:30:30 +0100, Scott wrote:

> On Tue, 20 Sep 2022 07:22:08 -0000 (UTC), jon <j...@nospam.cn> wrote:
>
>>On Mon, 19 Sep 2022 22:45:51 +0100, Graham. wrote:
>>
>>> I love the Tesla irony, but this is a non-starter isn't it?
>>>
>>> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-
switch-
>>the-uk-s-power-distribution-from-ac-over-to-dc
>>
>>I grew up with DC Mains and with all my early electrical experiments I
>>used rotary transformers. I obtained a variety of ex-gov/military bits
>>and pieces and was able to convert mains voltage 250v to 28vDC, 12vDC
>>and 400vDC.
>
> When was your place converted to AC (if you were still there, that is)?
> I think our house was originally wired for DC as some of the old
> switches were extremely heavy duty and fitted with springs. I was told
> this was to prevent arcing.

DC switches were of the over centre toggle type fast break and make or
over centre spring rotary switches.

>
> As a matter of interest, were any appliances unavailable? I assume
> lighting was interchangeable (as long as not fluorescent). Radiators
> would be okay. Ditto cookers and electric kettles. I believe radios
> were made AC/DC. Could a fridge be run on DC? Were DC televisions
> made?

Never had a fridge only larder

> Were red and black colours used? Was one terminal positive and the
> other neutral, or was the other terminal negative (eg +120V / - 120V)?
> Was an earth used in DC systems?

The wiring was VIR with red and black designations.

> Was it possible to have an electric clock in the absence of a mains
> frequency?

not economically

[Mike Humphrey]

IIRC some electric clocks were more or less clockwork clocks with a motor
replacing the spring - they still had a pendulum or escapement for the
timing. Presumably these would work on DC, and be as accurate as a
clockwork equivalent. Nothing like as accurate as a quartz clock of
course, unless the mechanism was unusually high quality.

Mike

[Colin Bignell]

On 20/09/2022 14:18, N_Cook wrote:

> On 19/09/2022 22:45, Graham. wrote:
>>
>> I love the Tesla irony, but this is a non-starter isn't it?
>>
>> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc
>>
>
> Southampton central power station was about the last UK plant to supply
> DC to nearby homes as late as mid 1960 IIRC.

Dreamland in Margate still had a DC supply at least into the 1970s. They
needed it for all the electric motors on the rides. I assume the
supplier rectified it from the grid.

> The deep-drilling and geothermal plant was built on the site, curiously.
> Oddly the underwater interconnectors between European coutries tend to
> be very high DC
>
>

--

Colin Bignell

[Colin Bignell]

That approach was used for some master clocks in master/slave clock
systems used in large buildings. Others were clockwork, with electric
winding.

--
Colin Bignell

[Colin Bignell]

On 20/09/2022 13:30, Scott wrote:
> On Tue, 20 Sep 2022 07:22:08 -0000 (UTC), jon <j...@nospam.cn> wrote:
>
>> On Mon, 19 Sep 2022 22:45:51 +0100, Graham. wrote:
>>
>>> I love the Tesla irony, but this is a non-starter isn't it?
>>>
>>> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-
>> the-uk-s-power-distribution-from-ac-over-to-dc
>>
>> I grew up with DC Mains and with all my early electrical experiments I
>> used rotary transformers. I obtained a variety of ex-gov/military bits and
>> pieces and was able to convert mains voltage 250v to 28vDC, 12vDC and
>> 400vDC.
>
> When was your place converted to AC (if you were still there, that
> is)? I think our house was originally wired for DC as some of the old
> switches were extremely heavy duty and fitted with springs. I was
> told this was to prevent arcing.
>
> As a matter of interest, were any appliances unavailable? I assume
> lighting was interchangeable (as long as not fluorescent). Radiators
> would be okay. Ditto cookers and electric kettles. I believe radios
> were made AC/DC. Could a fridge be run on DC?

Caravan and boat fridges often are. Use the Electrolux (aka vapour
absorption) cycle and they can run off gas as well.

> Were DC televisions
> made?
>
> Were red and black colours used? Was one terminal positive and the
> other neutral, or was the other terminal negative (eg +120V / - 120V)?
> Was an earth used in DC systems?
>
> Was it possible to have an electric clock in the absence of a mains
> frequency?
>
> I have tried to research on Google but there seems to be remarkably
> little detail.

--
Colin Bignell

[Tim+]

50Hz seems to be a particular good frequency for throwing your heart into
ventricular fibrillation. 60Hz is considered safer.

Tim

--
Please don't feed the trolls

[Max Demian]

Car clocks used to be DC of course. Before quartz they would be
clockwork with a small spring which would be wound up every couple of
minutes by a solenoid.

In DC mains days I expect most domestic clocks would be wind up. There
may have been a few battery electric ones with a balance wheel or
pendulum; I only remember the ones from the 60s or 70s which used
transistors.

Mains electric clocks were popular as they should keep perfect time
unless there was a power cut as they were synchronised to the mains
frequency; not really clocks at all, more "dials". Apparently in WW2
sometimes electric clocks went slow, then caught up again; people didn't
know whether to reset them or not.

If there was a power cut some synchronous clocks would restart so may be
slow; others stayed off or restarted backwards. There would be a knob to
restart them and ensure they started forwards.

--
Max Demian

[Scott]

I thought they had the potential to lose time during peak periods and
regained the time later, due to fluctuations in frequency based on
demand.

[Scott]

On 20 Sep 2022 14:58:56 GMT, Tim Streater <timst...@greenbee.net>
wrote:

>On 20 Sep 2022 at 14:12:52 BST, Joe <j...@jretrading.com> wrote:
>
>> On Tue, 20 Sep 2022 13:30:30 +0100
>> Scott <newsg...@gefion.myzen.co.uk> wrote:
>>
>>
>>> Were DC televisions
>>> made?
>>>
>> Yes, TVs of the Fifties were all AC/DC, with mains droppers (big
>> resistors) to get appropriate voltages. This was my parents' first TV,
>> bought around 1957:
>>
>> https://www.radiomuseum.org/r/ferguson_306t.html
>> https://www.vintage-radio.net/forum/attachment.php?s=bb23081888735c55e30c8be5e7442b9a&attachmentid=201452&d=1584945915
>>
>> It was definitely AC/DC. Six external controls plus the tuner, needing
>> vertical or horizontal hold adjustment every ten minutes or so.
>

>Yours had a tuner? Luxury! Ours was BBC only. Agree about the Vert/Horiz hold
>business.

I assume at some point it was tuned to the correct frequency for your
transmitter, possibly on installation.

[Ian Jackson]

In message
<440649020.685381882.434...@news.individual.net>,
Tim+ <tim.d...@gmail.com> writes

And transformers don't need as much iron, so are smaller and lighter.
>

--
Ian

[Ian Jackson]

In message <44qjih538jclmocr5...@4ax.com>, Scott
<newsg...@gefion.myzen.co.uk> writes

I once understood that synchronous electric clocks could be fast or
slow, but at 8am the mains was supposed to have had the correct number
of cycles in the previous 24 hours. Is/was this ever true? At the
moment, the mains is running a bit fast (and I see that wind is only
0.89GW!).
http://www.gridwatch.templar.co.uk/
--
Ian

[Andy Burns]

Ian Jackson wrote:

> I once understood that synchronous electric clocks could be fast or slow, but at
> 8am the mains was supposed to have had the correct number of cycles in the
> previous 24 hours. Is/was this ever true? At the moment, the mains is running a
> bit fast

AFAIK, it was and still is true, that there should be 4320000 mains cycles per
day. Maybe this chap counts them?

<http://mainsfrequency.uk>

[zall]

On Tue, 20 Sep 2022 23:18:29 +1000, N_Cook <div...@tcp.co.uk> wrote:

> On 19/09/2022 22:45, Graham. wrote:
>>
>> I love the Tesla irony, but this is a non-starter isn't it?
>>
>> https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-switch-the-uk-s-power-distribution-from-ac-over-to-dc
>>
>
> Southampton central power station was about the last UK plant to supply
> DC to nearby homes as late as mid 1960 IIRC.
> The deep-drilling and geothermal plant was built on the site, curiously.

> Oddly the underwater interconnectors between European coutries tend to
> be very high DC

Nothing odd about it, that avoids having to synch the frequency
of the UK service with the european services.

[Scott]

On Tue, 20 Sep 2022 17:59:58 +0100, Andy Burns <use...@andyburns.uk>
wrote:

Why 8 am though? This would be a difficult time to recover a
shortfall, during the morning peak. I was told that the correction
took place during the off peak.

[Roger Mills]

FWIW, it appears that the Yanks use AC for electrocuting people in their
electric chairs.

--
Cheers,
Roger

[Peeler]

On Wed, 21 Sep 2022 03:04:03 +1000, zall, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>

--
Retirednoguilt addressing trolling senile Rodent Speed:
"Obviously you have nothing but contempt and disregard for
everyone else's comments and opinions. You shouldn't waste another
second of your precious time trying to educate us. Just ultra isolate,
avoid this group as if it might infect you, and find another Usenet group.
MID: <spff82$i0d$1...@dont-email.me>

[Paul]

Mains is supposed to be plesiochronous with the atomic clock network.
A grid counts cycles, for the purposes of maintaining legacy analog
and legacy digital clocks.

https://en.wikipedia.org/wiki/Plesiochronous_system

It's possible for a grid, to be perpetually slow, and not be
able to make up the cycle count. This isn't a wand-waving job,
it takes an effort to maintain the clocks this way.

https://www.wired.co.uk/article/clock-slow-europe-electricity-power-serbia-kosovo

Delivering power has priority over cycle accuracy. If the
right conditions are not present on a grid, to inject
cycles, then it simply won't happen. It's possible
the clock corrections are done later in the day, rather than
at 2PM.

*******

A GPS gives position information, but it also delivers accurate time.
If you need to discipline a time-keeping device, GPS is one way to do it.

The LF transmitters offer a second way to do it (this is for the clocks
that have the radio receiver with tiny ferrite antenna inside them -- the
ferrite material for this, is made in Russia).

You can beat your local oscillator clock, against a HF radio reference.
But that isn't all that good of a method. I had an oven-stabilized 1MHz
clock, tuned by listening for a beat note on a shortwave radio. You
can use that, for getting the quartz oscillator reference "in the ballpark".

Even Cesium or Rubidium references, are GPS disciplined, the commercial ones.
And references like that can be obtained for around $1000 or so, whereas
years ago, they were quite expensive. We had a reference at work, and
had to run a cable up the side of the building, for our GPS antenna.
The building filtered out radio signals otherwise. And that's a good
thing. There was a significant amount of RF inside the building :-)

When your hand-held GPS loses lock, the clock piece inside
will free-wheel for ten or fifteen minutes before declaring
a problem. I have a GPS that does this (a GPS that used to
maintain the time on my WinXP machine).

Paul

[Peter Able]

Even when a TV had a tuner - overwhelmingly likely to be a turret tuner
- there was still the issue of your local transmitter frequency. Turret
tuners had 13 positions - but rarely 13 "biscuits" fitted.

Talking of safety, Turret tuners loved to hack into TV engineers'
fingers. Far worse than the occasional zap!

PA

[Harry Bloomfield Esq]

On 20/09/2022 13:30, Scott wrote:
> Were red and black colours used? Was one terminal positive and the
> other neutral, or was the other terminal negative (eg +120V / - 120V)?
> Was an earth used in DC systems?

I don't remember the DC, but it was when I was young. We then went to
210v AC. AC or DC, the wiring was red and black or near enough, shades of.

Our early TV' and radio were AC/DC and had tapping on droppers, or
later, tapping on transformers where AC only.

[Harry Bloomfield Esq]

On 20/09/2022 15:58, Mike Humphrey wrote:

> IIRC some electric clocks were more or less clockwork clocks with a motor
> replacing the spring - they still had a pendulum or escapement for the
> timing. Presumably these would work on DC, and be as accurate as a
> clockwork equivalent. Nothing like as accurate as a quartz clock of
> course, unless the mechanism was unusually high quality.

The AC ones had a pawl and spring mechanism, to force them to start up
running the right way. If they started the wrong way, the pawl would
begin winding the spring up and eventually force it to go clockwise. A
favourite trick of mine, was releasing the spring, so it 50/50 went the
wrong way.

A similar motor to a microwave turntable, which can run either way on
startup.

[Harry Bloomfield Esq]

On 20/09/2022 17:07, Max Demian wrote:
> Mains electric clocks were popular as they should keep perfect time
> unless there was a power cut as they were synchronised to the mains
> frequency; not really clocks at all, more "dials". Apparently in WW2
> sometimes electric clocks went slow, then caught up again; people didn't
> know whether to reset them or not.

That still happens, but not so obviously as the generators come under
greater load. They catch up when there is a surplus of generation.

>
> If there was a power cut some synchronous clocks would restart so may be
> slow; others stayed off or restarted backwards. There would be a knob to
> restart them and ensure they started forwards.

Yep, I remember those with buttons.

[Harry Bloomfield Esq]

On 20/09/2022 17:59, Andy Burns wrote:
> AFAIK, it was and still is true, that there should be 4320000 mains
> cycles per day.

There were only 4319999 last night :-)

[Harry Bloomfield Esq]

On 20/09/2022 19:06, Paul wrote:
> You can beat your local oscillator clock, against a HF radio reference.
> But that isn't all that good of a method. I had an oven-stabilized 1MHz
> clock, tuned by listening for a beat note on a shortwave radio. You
> can use that, for getting the quartz oscillator reference "in the
> ballpark".

I enquired of the BBC, back in the analogue days, how accurate their
line timebase was. The reply was that it was extremely accurate, and I
designed a reference based upon that, tapped from a portable TV, for
calibrating my instruments.

[Harry Bloomfield Esq]

On 20/09/2022 15:58, Tim Streater wrote:
> Yours had a tuner? Luxury! Ours was BBC only. Agree about the Vert/Horiz hold
> business.

You forgot the very technical thump on the side of the case :-)

[Harry Bloomfield Esq]

On 20/09/2022 15:47, jon wrote:
> The wiring was VIR with red and black designations.

Or two, maybe three core rubber, but equally bad colouring.

[Harry Bloomfield Esq]

On 20/09/2022 16:22, Colin Bignell wrote:
> Caravan and boat fridges often are. Use the Electrolux (aka vapour
> absorption) cycle and they can run off gas as well.

+1

[Harry Bloomfield Esq]

On 19/09/2022 23:48, John Bryan wrote:
> Typical small world thinking, they have never been near any sort of
> manufacturing plant that use large motors.

I have a number of times.

[Ian Jackson]

In message <tgci99$1hbbo$3...@dont-email.me>, Fredxx <fre...@spam.uk>
writes

>On 20/09/2022 14:18, N_Cook wrote:
>> On 19/09/2022 22:45, Graham. wrote:
>>>
>>> I love the Tesla irony, but this is a non-starter isn't it?
>>>
>>>
>>>https://greenlibdems.org.uk/en/article/2020/1383503/ac-dc-time-to-swit
>>>ch-the-uk-s-power-distribution-from-ac-over-to-dc
>>>
>> Southampton central power station was about the last UK plant to
>>supply DC to nearby homes as late as mid 1960 IIRC.
>> The deep-drilling and geothermal plant was built on the site, curiously.
>> Oddly the underwater interconnectors between European coutries tend
>>to be very high DC
>

>Hardly 'oddly'. The UK and European mains networks are asynchronous, so
>cannot be directly connected. Dielectric loss is significant in salt
>water, so DC is preferred on two counts.
>
And for the same power delivery, the peak voltage of DC is 0.707 of that
of AC - which eases the required breakdown rating of the cable.
--
Ian

[Bob Eager]

On Tue, 20 Sep 2022 20:08:46 +0100, Harry Bloomfield Esq wrote:

> On 20/09/2022 17:07, Max Demian wrote:
>> Mains electric clocks were popular as they should keep perfect time
>> unless there was a power cut as they were synchronised to the mains
>> frequency; not really clocks at all, more "dials". Apparently in WW2
>> sometimes electric clocks went slow, then caught up again; people
>> didn't know whether to reset them or not.
>
> That still happens, but not so obviously as the generators come under
> greater load. They catch up when there is a surplus of generation.

Many years ago, I went on an IEE visit to the CEGB control centre. There
were two clocks on the big wall. One was synchronous, the other crystal
or something.

They were given an absolite difference limit (1.5% I think) over 24
hours. But heads rolled if it reached half that.



--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

[Bob Eager]

On Tue, 20 Sep 2022 18:45:26 +0100, Peter Able wrote:

>>> Yours had a tuner? Luxury! Ours was BBC only. Agree about the
>>> Vert/Horiz hold business.
>>
>> I assume at some point it was tuned to the correct frequency for your
>> transmitter, possibly on installation.
>
> Even when a TV had a tuner - overwhelmingly likely to be a turret tuner
> - there was still the issue of your local transmitter frequency. Turret
> tuners had 13 positions - but rarely 13 "biscuits" fitted.
>
> Talking of safety, Turret tuners loved to hack into TV engineers'
> fingers.
> Far worse than the occasional zap!

Our second turret tuner TV was vastly over engineered (so of course my
dad bought it).

It had a set of 'piano keys' above the screen. Press one and a motor
rotated the turret to the selected position...

[wrights...@f2s.com]

On Tuesday, 20 September 2022 at 16:22:27 UTC+1, Colin Bignell wrote:

> Caravan and boat fridges often are. Use the Electrolux (aka vapour
> absorption) cycle and they can run off gas as well.

They are very inefficient.

Bill

[wrights...@f2s.com]

On Tuesday, 20 September 2022 at 19:45:31 UTC+1, Peter Able wrote:

> Even when a TV had a tuner - overwhelmingly likely to be a turret tuner
> - there was still the issue of your local transmitter frequency. Turret
> tuners had 13 positions - but rarely 13 "biscuits" fitted.

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.

https://en.wikipedia.org/wiki/Electric_chair

"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.

https://www.vox.com/2015/5/13/8598655/north-korea-execution

Paul

[Rod Speed]

They stole that from the british.
https://en.wikipedia.org/wiki/Blowing_from_a_gun

[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

[Peeler]

On Wed, 21 Sep 2022 09:33:15 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>

--

Tim+ about trolling Rodent Speed:
He is by far the most persistent troll who seems to be able to get under the
skin of folk who really should know better. Since when did arguing with a
troll ever achieve anything (beyond giving the troll pleasure)?
MID: <1421057667.659518815.743...@news.individual.net>

[Joe]

On Tue, 20 Sep 2022 17:07:20 +0100
Max Demian <max_d...@bigfoot.com> wrote:

>
>
> Mains electric clocks were popular as they should keep perfect time
> unless there was a power cut as they were synchronised to the mains
> frequency; not really clocks at all, more "dials". Apparently in WW2
> sometimes electric clocks went slow, then caught up again; people
> didn't know whether to reset them or not.

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.

>
> If there was a power cut some synchronous clocks would restart so may
> be slow; others stayed off or restarted backwards. There would be a
> knob to restart them and ensure they started forwards.
>

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.

--
Joe

[The Natural Philosopher]

On 20/09/2022 17:44, Ian Jackson wrote:
> I once understood that synchronous electric clocks could be fast or
> slow, but at 8am the mains was supposed to have had the correct number
> of cycles in the previous 24 hours. Is/was this ever true? At the
> moment, the mains is running a bit fast (and I see that wind is only
> 0.89GW!).
> http://www.gridwatch.templar.co.uk/

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

--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

[Harry Bloomfield Esq]

On 21/09/2022 00:56, Paul wrote:
> 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.

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

[Harry Bloomfield Esq]

On 20/09/2022 23:31, wrights...@f2s.com wrote:
> They are very inefficient.

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]

On 20/09/2022 23:36, wrights...@f2s.com wrote:
> 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.

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

[wrights...@f2s.com]

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.
https://www.justkampers.com/dometic-coolmatic-crx50-premium-compressor-cabinet-fridge-freezer-48-litre-stainless-steel-finish.html?msclkid=36c239fabdde15a5a24a5ad047357ad8&utm_source=bing&utm_medium=cpc&utm_campaign=JK%20UK%20%7C%20Shopping%20%7C%20PLAs%20%7C%20Top%20performing%20products&utm_term=4587506115097761&utm_content=Top%2010

Bill

[wrights...@f2s.com]

http://tx.mb21.co.uk/info/405/bbc/

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.

[Colin Bignell]

They work fine on canal boats.


--
Colin Bignell

[Bob Eager]

On Wed, 21 Sep 2022 10:31:13 +0100, Joe wrote:

> 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.

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]

On 21/09/2022 13:58, Bob Eager wrote:
> On Wed, 21 Sep 2022 11:18:24 +0100, Harry Bloomfield Esq wrote:
>
>> On 20/09/2022 23:36, wrights...@f2s.com wrote:
>>> 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.
>>
>> I wonder why they had so many positions, when there was only a choice of
>> one or other - BBC or ITV?
>
> 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.
>

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

[Bob Eager]

Same here. But the three are all my region!

[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]

On 21/09/2022 13:30, Fredxx wrote:

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

Err, what?

[SH]

I seem to recall that cars were originally positive earth, but this
changed over to negative earth due to corrosion issues?

[Harry Bloomfield Esq]

On 21/09/2022 13:58, Bob Eager wrote:

> 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.

The turrets were 405 line VHF, BBC2 came along it was on 625 line UHF
and via a separate tuner. After the 405 VHF turrets, the dual standard
sets came along able to tune both VHF and UHF. Eventually VHF was shut
down, and all were on UHF, then along came colour.

[Harry Bloomfield Esq]

On 21/09/2022 13:33, Peter Able wrote:
> 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.)

Thanks, I have only vague recollections of the era.

[Fredxx]

Not any more, they've been banned on new builds.

[Joe]

Back in the bad old baseband TV broadcast days, transmitted video was
locked to an atomic standard, at least the BBC channels were. Mostly I
used it to set camera master oscillators using a dual-channel scope,
but it could also be used to genlock a Tektronix TV sync generator,
which had a 10MHz output.

--
Joe

[Joe]

Possibly more to do with PNP transistors being superseded by NPN, for
which a positive supply rail was easier to deal with. Also electronic
ignition was beginning to appear, which used a large NPN transistor.

With dynamos and no onboard electronics, it was easy to reverse the
car's polarity, but alternators were definitely of fixed polarity.

--
Joe

[Max Demian]

I believe that was the case.

This link seems to think there's not much pro or con:
https://www.restore-an-old-car.com/positive-ground-cars.html

--
Max Demian

[Peter Able]

Just don't ask me about what happened 70 minutes ago !!

PA

[Peter Able]

On 21/09/2022 13:58, Bob Eager wrote:

> On Wed, 21 Sep 2022 11:18:24 +0100, Harry Bloomfield Esq wrote:
>
> And it allowed for future expansion. It was easy enough to add BBC2.
>

AFAIK no turret tuners could be adapted to receive UHF. Dual Standard
sets were awful bodges.

Good for the repair business, though. Those foot-long cheap slide
switches. Quick spray with switch cleaner and a few operations of the
switch. Take the call-out fee. "See you soon!"

PA

[Colin Bignell]

It is a while since I have been on the canals. My late partner wouldn't
steer and there came a point where she couldn't work the locks either.

--
Colin Bignell

[NY]

"Harry Bloomfield Esq" <a...@harrym1byt.plus.com> wrote in message
news:tgf8s5$1pacu$3...@dont-email.me...

Except that VHF was shut down *after* the advent of colour. I think it
finished some time in the 1980s, and colour began in the late 60s and became
available on all transmitters (AFAIK) by the early 1970s.

[Harry Bloomfield Esq]

On 21/09/2022 16:29, Joe wrote:
> Mostly I
> used it to set camera master oscillators using a dual-channel scope,
> but it could also be used to genlock a Tektronix TV sync generator,
> which had a 10MHz output.

It was my own design of that, which I built and used. One LED to
indicate power, another to indicate lock. Probably still on the shelf of
my workshop, but useless now.

[Harry Bloomfield Esq]

On 21/09/2022 18:39, NY wrote:
> Except that VHF was shut down *after* the advent of colour. I think it
> finished some time in the 1980s, and colour began in the late 60s and
> became available on all transmitters (AFAIK) by the early 1970s.

Well, the main ones at least.

[Ian Jackson]

In message <tgf5c7$1aek$1...@gioia.aioe.org>, SH <i.lov...@spam.com>
writes

I understood that it is positive earth that gives less corrosion, but in
vehicles they eventually found that, in practice, there was little
difference.
--
Ian

[wrights...@f2s.com]

I can get every ITV region and every BBC region.

Bill

[Max Demian]

On 21/09/2022 16:57, Peter Able wrote:
> On 21/09/2022 13:58, Bob Eager wrote:
>> On Wed, 21 Sep 2022 11:18:24 +0100, Harry Bloomfield Esq wrote:
>>
>> And it allowed for future expansion. It was easy enough to add BBC2.

> AFAIK no turret tuners could be adapted to receive UHF.  Dual Standard
> sets were awful bodges.

I assume UHF only TVs always used varicap tuning, usually with presets
(except some portables).

--
Max Demian

[SH]

So you managed to get ITV Meridian and BBC South along with BBC 1 Wales
and ITV Wales at your humble abode in Yorkshire using an amplified Yagi
Uda quad phased array on a 20 m long pole then? :-D