Jamming the Germans
BBC Heritage on behalf of Ken Lansdowne's memory of 01/01/1940 - 30/12/1940
In the latter years of World War 2 I joined the BBC as a 'Youth in Transmitters' at Brookmans Park. I was shown round the control room and, having a keen interest in electronics, I was soon familiar with the amplifiers and peak programme meters. One instrument in the control room mystified me. It was labelled 'Noise Generator', and its finish was not up to the usual BBC standard.
I asked various engineers what its function was, and was told the following: If the Germans captured a UK broadcasting station either by invasion or by a commando-type raid, they could cause chaos by transmitting false information or instructions to the population - as we did to the Germans by the Aspidistra transmitter. To prevent this, if a station was captured, other BBC stations would change frequency, sit on the captured station and jam it. The jamming noise was produced by the device labelled ‘Noise Generator’.
The device was switched on for my benefit, the 'on' switch being operated by a key which was kept in a secure place. The sound it produced was a rhythmic wailing noise which no doubt would have been most effective in jamming the subversive programme. All the medium wave transmitters were equipped with a noise generator, made no doubt in a hurry in 1940 when invasion was believed to be imminent.
I was warned that this was most secret, and that if I disclosed the fact that the BBC had a jamming network there would be dire consequences.
It was many years after the war before I mentioned it, and the people to whom I spoke flatly denied it had ever existed.
There the matter rested until just before I retired, when I was asked to look through a pile of hand-written documents prior to them being shredded, and to my astonishment I found the circuit of the Noise Generator. The circuit design was simple but clever, and the date of the plans, June 3 1940, is significant. The Low Countries had been invaded, and France was capitulating. The prospects for Britain were very bleak, and these devices were obviously designed and made in a great hurry.
The designer was C.G. Mayo, who was a very brilliant engineer who worked as I did in Research Department at Kingswood Warren. He never mentioned his wartime work, and by the time I found his design he had died. What a pity - it would have been fascinating to know the background to the installation of the network. Such a network would have to be authorised at a high level, and no doubt the minutes of such authorising will be gathering dust somewhere in the BBC archives.
I have an interest in old valve equipment, and working from the circuit using the same valves and components I have built a precise replica of the unit. When I switched it on it produced exactly the same sound I remembered from sixty years before. I have now passed this on to the BBC Heritage Collection.
This memory was submitted to the Memoryshare web service by the BBC Heritage Team on behalf of Ken Lansdowne.