I wonder if the neon on the snake oil voltage optimisers I have installed [1] go out when the voltage drops[2]?
[1] customers choice and I tried to talk them out of it. But so far I have only had two daft sods have them fitted. [2] sorry that was a rhetorical question:-) The neon that is labelled up as "optimising" is connected to the incoming supply.
In the case I was referring to it was 405, so 10,125 Hz.
What I found is that the brain seems to develop a notch filter at 10,125Hz.
Whilst a mains locked SPG would typically vary ±1% over time, the rate of change would be very slow indeed and not really noticeable.
When the genlock was enabled it only had a few seconds to sync to the incoming signal and as this had to be at frame, rather than field rate, it could be up to ±20mS out, so it could be quite a race. The master oscillator and the whole sync divider chain would change frequency which would, of course, also affect the line sync, causing the whistle to move rapidly out of the notch, at which point it became very audible until it resumed its normal pitch.
At Programme junctions, add breaks, etc., the sources were changed at the flick of a switch so the line sync could only be a maximum of ±49µS out so, at worst, you might detect a faint click if you were close enough. The field error was no more than ±10mS and dependent on the direction of the error, might either cause to the end of the frame scan to terminate early or to roll quickly up the screen but as these switching points were always done during a period of black level, the eye never saw anything but a quick flicker, if that.
NY submitted this idea :
It was a white square on the top right, with a rolling series of lines, wasn't it? It was put in so the local studios could sync with it.
I thought the idea of a genlock was that you synchronised the frequency and phase of the local device (eg the regional studio) to the incoming signal (eg the national centre that was about to hand over to regional) *before* the changeover, so it has plenty of time to get established before you make a seamless cut or even fade.
I forgot to add that you need to account for 2 x the signal transit time between the central studio and the region, so the region must synchronise slightly early of the incoming signal to allow for that. I presume setting the correct delay for each source is a skilled job.
We had a 90 minute power fail on Monday night at 5:30PM in West Sussex. Unusually, there was no flickering before hand, it just went off. Phut.
Today, in the Metro I read that 50,000 people lost power in Portsmouth on Monday evening too, which is a coincidence. The article said SSE was investigating. In West Sussex, previously a Seeboard area, we now have 'EDF'.
I wonder if outlying villages were sacrificed to restore power to Portsmorth ?. maybe the Queen Elizabeth is in port ?, it needs an awful lot of power by all accounts (sometimes).
The last time (2008) my plugin Tchibo meter showed the voltage as
187v I phoned EDF, and their response was 'is that a problem' ?. 2 months later the thermostat on my Liebherr fridge failed.??I used to have 247v, but for many years it seems to hover around
225v.I notice that my 35-yo ebac homedry dehumidifier says 240 volts,
350 watts. I wonder if running at 225v will accelerate its demise ?.
Do cruise ships at moorings take power from the shore, or do they keep their engines ticking over to provide "hotel power".
I was once on a cruise liner that experienced a power failure while it was docked, and we were told that the engine which powered the generator had failed, which suggests that power is not taken from a shore supply.
the whole of England, Walesd & Scotland had a comon frequency, courtesy of the National Gid - NI had its own
>
There was also "Slavelock" where the remote source was steered into synchronism with the destination. This initially required an audio circuit back to the source, but later the syschronising signals were sent in the VI period, so all that was needed was an off-air signal. Interrnally between TC and LG there was slavelock so that sources in Lime Grove were synchronous at TC.
On my BBC Tech Ops course at Evesham in the early 60's, the course band was called "The Rolling Humbars"
Somewhat ironically, Tomorrow's World on BBC4 now suffered a transmission dropout with a sudden cut to another programme's studio or still.
There are still skilled jobs in broadcasting, but fewer skilled people doing them.
Judith Hann has done a whole interview without once starting a sentence with "so".
Owain
I preserved this pair of cue dots for posterity
I wanted to call our mobile disco "Blue Lateral" but my partner overruled me.
And before anyone asks, the cross channel UK <> France submarine cable uses DC, and no attempt is made to synchronise our respective grids.
I have a 1950s TV. I can understand why mains lock was still needed. Yes it was nice looking consumer goods, but in some ways it's primitive. 1930s techology screen, not even an ion trap.
That was normal in B&W TVs.
NT
PSU regulation became popular in the 80s. A minority used it before then, but most just designed the circuitry to cope with varying HT.
NT
easy way to get to the tea/biscuits/loo first
bad psu regulation, maybe near flat batteries
There's probably software somewhere to fix it, albeit at loss of effective bit rate.
NT
no
NT
You ought to try getting your head around why some things are working and some not when you've been woken up by something unknown at
0300... I didn't believe my voltmeter either and dug out a filament lamp. Turned all the main switches off apart from one and only left one ring main powered on that with stuff unplugged apart from the filament lamp as a tell tale.Can't remember if I reported it then or just went back to bed. The lamp was off when I got up and stayed off for the next 36 hours. The cause was an ice storm that brought the lines down in multiple places, the wires were enacsed in an inch or more of ice. The resultant physical shocks when the lines broke were enough to snap a number of poles.
That's when I found that the generator uses about 1l of red per hour keeping the heating hot and the fridges/frezers cold.
Distribution is the 3 phases only. Weird things happen if you get a break in one or more of the phases as the load across the phases becomes some what unbalanced.
The center point of the three phases, aka the neutral is bonded to real earth at the primary substation. The output side center point (or one of the output terminals of a single phase transformer) is also bonded to real earth. This means the neutral is the reference point at both ends. With the three phases equally loaded the three phases are 415 V apart and each one 240 V to neutral (or what ever the equivalents are at 11 kV...). Break one or two of the phases and the resultant load imbalance "drags" the neutral away from it's center point towards the still loaded phase(s). But the neutral is the reference so the effect is to reduce the phase <> neutral voltage on the still connected phases. This also means that the phase <>
neutral voltage of the section of line with the break but still connected to the primary substation rises by the same amount.
One would assume that there is over voltage detection and protection but with the the supply being nominally 230 V and the tolerance max
253 V you have 23 V reduction from nominal on one phase before the upper tolerance is reached on others and there's bound to be several tens of volts head room in the protection. Meaning that a brown out to 180/170 V is quite possible before any overvoltage detection gets upset and trips the lot.I think... The line downstream of the break thus not connected to the priamry substation is floating so I guess that sits midway between the two still connected phases which is probably pretty close to where the neutral reference has been dragged mean that it is effectively "off".
Two phases open circuit, hum, not sure 415 V phase <> neutral? Giving an over volatge trip?
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