Load shedding by Smart Meters

[JohnW2]

A year or two ago France radio decided they no longer wanted to broadcast on LW. But the Allouis transmitter on 162kHz also provided sync signals for railway station clocks throughout France. It was found the power could be substantially lowered without affecting the clocks. So that was done, the radio modulation turned off, and France radio no longer paid for it. It is still possible to tune in the silent carrier to this day.

Interesting.

My understanding is that a lot (most?) of the 'radio controlled clocks' in use in the UK use the time signals from Droitwich - so maybe something similar will happen here. If it did, I would imagine that if the much lower-powered transmission was enough to synch cheopo 'radio-controlled clocks', the same low-powered transmission would probably be able to successfully continue to provide the teleswitch service.

At least in the past, the Droitwich 198 kHz signal (the frequency of which is controlled by an atomic clock) was also used as a 'frequency standard'. If that's still the case, that's something else that might need to continue with a much lower-powered transmitter.

Kind Regards, John

 

[winston1]

My understanding is that a lot (most?) of the 'radio controlled clocks' in use in the UK use the time signals from Droitwich -

No some radio controlled clocks use the 60kHz MSF signal from Anthorn (previously located at Rugby). Others use the 77.5kHz signal from a station near Frankfurt.

 

[JohnW2]

No some radio controlled clocks use the 60kHz MSF signal from Anthorn (previously located at Rugby). Others use the 77.5kHz signal from a station near Frankfurt.

Fair enough, but, as far as I am aware, Droitwich still transmits time signals - so who/what uses them, I wonder?

Kind Regards, John

 

[Harry Bloomfield]

My understanding is that a lot (most?) of the 'radio controlled clocks' in use in the UK use the time signals from Droitwich -

No, the radio clocks receive MSF from Anthorn, which used to be MSF from Rugby 60Khz, which I wrote decode software for several decades ago. Some clocks use the German equivalent from Mainflngen on 77Khz.

NPL is at Droitwich and that 198Khz signal is a frequency standard and a 25bit time source standard. I have used the frequency standard, many times for calibration purposes, but never tried decoding the time standard.

 

[JohnW2]

No, the radio clocks receive MSF from Anthorn, which used to be MSF from Rugby 60Khz, which I wrote decode software for several decades ago. Some clocks use the German equivalent from Mainflngen on 77Khz.

Fair enough - with two of you saying exactly the same thing, it must be true

NPL is at Droitwich and that 198Khz signal is a frequency standard and a 25bit time source standard. I have used the frequency standard, many times for calibration purposes, but never tried decoding the time standard.

Same here. In the days before Droitwich changed from 200 kHz to 198 kHz (which I think was about 30 years ago), that 200 kHz frequency standard was very useful for 'fine tuning' the 100 kHz oscillator in a 'crystal calibrator' (which was the best means of 'frequency measurement' that most of us had back in the 60s/70s).

I don't think I ever knew what resulted in the frequency change - is there a simple explanation?

Kind Regards, John

 

[DetlefSchmitz]

I seem to remember there was an international agreement to align all frequencies on some standard channel spacing. Probably 6kHz.

 

[Harry Bloomfield]

I don't think I ever knew what resulted in the frequency change - is there a simple explanation?

Kind Regards, John

I a bit vague on it, but I half remember is was to avoid interference with some other service..

When it changed, I built a gadget to use the old 625 line timebase, with a PLL to give a precise 1Mhz reference. The TV was a very accurate sub-standard.

 

[Harry Bloomfield]

I seem to remember there was an international agreement to align all frequencies on some standard channel spacing. Probably 6kHz.

Yes, that was it !

 

[bernardgreen]

The frequencies were changed as part of a pan European "re-alignment" of broadcasting services.

In 1983 the transmission of data was added to the long wave service by the use of phase modulation of the 198kHz carrier . This type of modulation was un-detectable by domestic radio receivers but opened up the way for remote control of the electricity network and various other "systems"

There is a good history of Droitwich transmitting station HERE

 

[Harry Bloomfield]

There is a good history of Droitwich transmitting station HERE

I have read a few historical write ups about the Tx, but never came across that one. Thanks, a good read!

 

[JohnW2]

In 1983 the transmission of data was added to the long wave service by the use of phase modulation of the 198kHz carrier . This type of modulation was un-detectable by domestic radio receivers but opened up the way for remote control of the electricity network and various other "systems"

Yes, I was aware of that.

I have to say that I have always felt that the differences between phase modulation and frequency modulation are pretty subtle, the former essentially being a type of the latter (mathematically, it certainly is).

There is a good history of Droitwich transmitting station HERE

Thanks.

Kind Regards, John

 

[JohnW2]

When it changed, I built a gadget to use the old 625 line timebase, with a PLL to give a precise 1Mhz reference. The TV was a very accurate sub-standard.

By the time the change occurred, I really had no need for a 'crystal calibrator', so I did not need to address the issue.

However, if I had had that need, I suppose that it would have been straightforward enough, since the 100 kHz oscillator was divided down to 1 kHz (with lots of harmonics), so that I would still have had an 'output' at 198 kHz to compare with the transmitted 198 kHz standard (and hence be able to tweak the crystal oscillator appropriately to 'calibrate').

Kind Regards, John

 

[Harry Bloomfield]

I liked to be able to check my test gear was accurate, I have three commercial grade frequency counters, so I needed to check they were accurate.

 

[bernardgreen]

differences between phase modulation and frequency modulation are pretty subtle,

With Phase Modulation there is no overall affect on the carrier frequency there will be 198,000 cycles in any given second. The last zero crossing point of the carrier waveform may be slightly displaced timewise. The carrier can be used as a reference frequency

With Frequency Modulation the number of cycles per second will be more or less 198,000 per second. With a NRZ data format the frequency can be 199,000 kHz or 197,000 kHz for long periods of time. The actual deviation from 198,000 depends on the depth of modulation and permitted band width. The carrier cannot be used as frequency reference.

NRZ = Non Return to Zero

 

[winston1]

NPL is at Droitwich and that 198Khz signal is a frequency standard

NPL is at Teddington, though the transmitter is at Droitwich.