Warning meters in 300,000 homes could stop working

My understanding, is that BBC long wave radio transmissions including the radio teleswitch signals are due to be ceased in the near future.

The long wave transmitters use very large glass valves and supplies of replacements are claimed to be limited. Such large and specialised valves were never a stock item. It cant be that hard to make them to order, as used to be done.

Coded messages inserted into BBC long wave radio signals are also reputedly used to pass instructions to our nuclear submarines, a matter of some importance.

Back when I worked at the BBC, over 40 years ago, we had a visit to the Droitwich transmitter. Even then, one look at it and it was astounding that they were able to keep it going. As you say, VERY large valves. It was already on borrowed time then. Wonderful place to visit though! It would make a wonderful museum (in a very similar vein to how Kew Bridge pumping station is) but sadly probably mainly appealing to engineering nerds like me...

Keeping things like that going are more a question of need/demand and perhaps political will power. The sort of folk that make elements for particle accelerators and electron microscopes (and we have both in Britain) would be perfectly capable of making (or re-cathoding ) transmitter valves- the diagrams are available, - if anything it's not even that fiddly compared to making, say, a laser tube. The real problem is that nostalgia does not pay, and longwave, and medium wave to an extent, are quite expensive to run, and worse, at least in the UK, are not protected from the rise of interference from switching power supplies, ADSL and so on, and are almost unusable in some built up areas.

Mike.

Hello Andy:

According to my book "The Saga of Marconi Osram Valve on Page 197 it highlights Droitwich running at a Frequency of 200 kHz (1500 Wavelength ) Power 150 Kw  with an opening date of October 1934.

Peter Brooks

Palm Bay 

Hello Mike:

I really doubt that anybody in the UK has the ability to reneck (you called it re-cathoding) the water cooled transmitter tubes(valves). Many had tungsten filaments not coated/nickle cathodes.

By the way one of the jobs I had in my youth was renecking CRT,s.

Peter Brooks

Palm Bay FL 

Well, I beg to differ, having worked along side both some folk who were able to successfully re-cathode a couple of argon ion laser tubes that the US manufactures assured us could not be done, opening up and re-sealing and annealing  a glass water jacket like a big Liebig condenser,  and also having seen the dedicated vacuum devices built for Alice - the UK one at Daresbury - That is not to be confused with  the one with the same moniker at CERN, which had a really substantial RF-line with provision to alter the phase for energy recovery - allowing removal of energy from the particles on each lap, or acceleration, at the flick of a switch, to reduce the induced radiation one would get from letting unused bunches of particles  crash land.
Then in the 'company' leagues rather than just teams of academics or  specialists, we have EEV == E2V , the only place I have seen so many operational glass lathes in one place. ..

We have the skills to do all sorts in the UK. We may lack the organization or the will-power.
Mike

Mike.

Hello Mike:

I must admit that I never worked on the big Transmitter tubes (made for Marconi usually designated with a CAT number- CAT6 ) however we used similar tubes for providing RF heading when making regular receiving and audio tubes. At one time one of my jobs was a to start up these caged RF systems..

Peter Brooks

Palm Bay FL .

Hello Mike:

It should also be noted that some transmitter tubes were also "hand made" by a glass blower, using Silica glass (pure SiO2) not lower temperature glass.

I had the opportunity a couple of times, to see the glass blower make these tubes envelopes..  

Peter Brooks

Palm Bay FL

Hello Mike:

It should also be noted that some transmitter tubes were also "hand made" by a glass blower, using Silica glass (pure SiO2) not lower temperature glass.

I had the opportunity a couple of times, to see the glass blower make these tubes envelopes..  

Peter Brooks

Palm Bay FL