BBC Droitwich Transmitter

[KeithsTV]

While clearing up the loft at the weekend I came across these two BBC information sheets on the LW & MW transmitters at Droitwich. I think I got them when I visited the station back in 1968 on a trip organised by my physics teacher from school. We got to see most of the station and I remember listening to the output of a simple crystal set right next to the LW transmitter. As the LW transmitter comprised two 200kW transmitters in parallel we were also told that when they wanted to do maintainance on one they just turned it off. I commented "Don't you lose some listeners?" The reply was "Only a few fringe area listeners and we're not too bothered about them" Each of the LW transmitter output stages was a single valve with an anode current of about 14A at 14kV according to the meters on the cabinet.

Living in south Birmingham, about 8 miles from the transmitter, with a 100ft aerial and a good earth I measured about 1v dc from the output of a crystal set when tuned to the LW transmitter. Due to the high signal levels I used to comment to friends at school that on a crystal set I could get Radio 1, Radio 2 and Radio 4....all at the same time

Keith

[Skywave]

Hi Keith -
Yes - that photo brought back a few memories!
Whilst undergoing basic training at a Government R&D establishment in Cheltenham, my student colleagues & I visited the Droitwich Tx Site in 1969.
An experience never forgotten. They don't make them like that anymore . . . or do they . . .

Al. / Skywave.

[kalee20]

Keith,

Thank you so much for sharing these handouts with us. I'll be printing them and reading them with interest!

When you listened with your crystal set beside the station, did it have enough power to operate a loudspeaker by any chance?

[KeithsTV]

Hi Kalee20

Not exactly a loudspeaker but I think it was a telephone earpiece. There was no aerial but as you would expect there was plenty of signal. From memory there was a TV in one of the staff rooms which had permanent patterning due to the high levels of RF.

Keith

[russell_w_b]

Originally Posted by KeithsTV

While clearing up the loft at the weekend I came across these two BBC information sheets on the LW & MW transmitters at Droitwich.

Keith

In case you haven't already seen them, there's some pics of Droitwich I took when I was attached there in 1984. They're on my 'Flickr' site at: http://www.***********/photos/russell...7603792453070/

Thanks for publishing the sheets!

[M0AFJ, Tim]

Originally Posted by Skywave

Hi Keith -
Yes - that photo brought back a few memories!
Whilst undergoing basic training at a Government R&D establishment in Cheltenham, my student colleagues & I visited the Droitwich Tx Site in 1969.
An experience never forgotten. They don't make them like that anymore . . . or do they . . .

Al. / Skywave.

Hi Al

Yes they do!, do a search for `Continental Electronics', they are based in Texas (where else) and build big broadcast transmitters still using valves (tubes), I'm just bidding a job using a 4 - 32MHz 100kW CW Amplifier, but this is solid state as we needed full instantanious bandwidth

Tim

[Ray Cooper]

Thanks for those files, they brought back a few memories.

One interesting item that wasn't mentioned in the write-up was that the entire station spent the first few years of its existence running off diesel power... the National grid hadn't got as far as Wychbold in those days. Also, there wasn't a decent water supply or sewage disposal system, so the station had its own - water pumped from a deep bore-hole. Maintenance of the sewage system was not one of the most popular maintenance items ("just pop down and measure the thickness of the crust, old boy...")

And in those days also, the transmitters were water-cooled using an outside cooling-pond system, which at various times sported good displays of goldfish. Precautions were taken to ensure that they didn't get sucked up the intake pipes.

The photo is interesting, too. In later years, the control desk was moved from its indicated position into a separate room - it was hard to quality-monitor the output (note the large monitor speaker) with all that noise competition from the TXs.

In even later years (post-1990) everything shown in that photo had disappeared. A further re-engineering scheme meant that much less room was needed, and the TX hall shown was simply demolished - the present front of the TX block is more or less the same as the back wall of the hall shown. The original station facia (listed) was dismantled piece-by-piece and later grafted back on to the new front wall of the block (see here:
http://tx.mb21.co.uk/gallery/droitwi...twich-hall.php )

[KeithsTV]

When we went round the site back in 68 we were shown the generator hall and the inputs from the national grid. I recall there may have been two feeds from the grid with two key operated switches and only one key to avoid shorting out the grid.

I'm sure the monitor desk was in a different room back then as it was quite noisy in the Tx hall.

Back in the 80s I used to go up to the Lickey hills, south of Birmingham, and from the car park the masts were quite prominent. I'm sure I've got a photo taken from the car park showing the masts. I'll dig it out when I get home. May bring back more memories.

Keith

[John Robson]

There is a interesting film discussing the construction of Droitwich on this
website.

http://www.bbceng.info/videos.htm

Looks to be using different transmitter equipment when it first opened.

[geofy]

Originally Posted by kalee20

Keith,

Thank you so much for sharing these handouts with us. I'll be printing them and reading them with interest!

When you listened with your crystal set beside the station, did it have enough power to operate a loudspeaker by any chance?

A loudspeaker could never be driven just by a crystal set, but I did build a crystal set and put a single germanium transistor on the output of the detector along with a 4.5 torch battery with the collector connected to the primary of a speaker output transformer on the back of an eight inch speaker and that worked very well when connected to a long wire aerial, picked up the London transmitter loud and clear.

Geof

[Skywave]

Originally Posted by Skywave . . .

They don't make them like that anymore . . . or do they? . . .

Al / Skywave.

------------

Yes they do! Do a search for `Continental Electronics'. They are based in Texas (where else) and build big broadcast transmitters still using valves (tubes).

Tim

---------------

Ah-Ha! Someone took the bait . . . & did the searching for me!

I'm obliged to you Tim. Thank you.

Al / Skywave.

[Skywave]

Originally Posted by John Robson

There is a interesting film discussing the construction of Droitwich on this website:
http://www.bbceng.info/videos.htm

I can't thank you enough for bringing that to the Forum! I found it absolutely riveting! I was particularly taken by the crisp military-style of 'getting things done'. Classic Vintage Wireless stuff.
And my! How things have changed.

Al / Skywave.

[russell_w_b]

Originally Posted by KeithsTV

I'm sure the monitor desk was in a different room back then as it was quite noisy in the Tx hall.

The monitor desk was in the room behind the doors at the other end of the transmitter hall to where it is shown in the pamphlet photograph. The monitor desk in the pamphlet photo was used for running the transmitter HT down after closedown and back up again in the morning.

The time in-between was spent polishing valves (and other maintenance, of course!).

[peter_scott]

Originally Posted by geofy

A loudspeaker could never be driven just by a crystal set,
Geof

Hi Geof,

I'm 20 miles from our Medium/Long wave transmitter but have in the past been able to hear and make out the speech whilst standing 15 feet away from a BTH horn loudspeaker connected to a BTH crystal set. It definitely is possible.

Peter

[geofy]

Originally Posted by peter_scott

Hi Geof,

I'm 20 miles from our Medium/Long wave transmitter but have in the past been able to hear and make out the speech whilst standing 15 feet away from a BTH horn loudspeaker connected to a BTH crystal set. It definitely is possible.

Peter

Hi Peter

The BTH () horn loudspeaker must be a high impedence type, which is working like an amplified headphone. But for ordinary speakers a valve or transistor is required.

Thanks

Geof

[Nickthedentist]

Originally Posted by geofy

BTH ()

= British Thomson-Houston Co. Ltd

See http://www.sparkmuseum.com/HORNS.HTM

[geofy]

Thanks Nick, new one on me, quite a collection, but the first cone speakers must have been a revelation after listening to these horns. Better get back ot

Geof

[SWB 18]

The control desk shown in the original photo at the start of the thread was preserved in the 'Droitwich Calling' room at the Droitwich Spa Heritage Centre. It can be seen in this link
http://www.compulink.co.uk/~rowe/dro...wichindex.html
I havn't been for several years now, but assume it is still there....

More info on the history of Droitwich, or DEI as it was sometimes known, take a look at
http://www.bbceng.info/Operations/tr...h_calling2.pdf

Attached are three photos of the inside front of the building shortly before the front section was demolished some years ago. The original building facade was carefully removed stone by stone and replaced on the revised, smaller building.

The first photo shows a view of where the control desk stood - you can just about make out the severed wires sticking out of the floor.

The second shows the remains of the control desk which lived in a room towards the front of the building. Home to many a Technical Assistant (TA) over the years...... This can be seen in a happier state in Russell's photos in his link earlier in the thread.

The third is a view from approximately underneath where the control desk stood looking towards the front of the building. I think that the square window upstairs on the left of the central double doors was the control room window. Well placed for the TA to spot problems in the transmitter hall such as smoke, fire & flashovers from the tx's he was monitoring......

Phil.