[Gllug] Norman Lamb MP

[Chris Bell]

On Sun 12 Oct, Adrian McMenamin wrote:
> 
> On Sunday 12 October 2003 15:00, Chris Bell wrote:
>  Areas around power
> > transmitters such as Daventry have such high levels of radiation that the
> > transmissions can be heard on a damp day as the induced voltages cause
> > arcing in the surrounding trees, 
> 
> Really? Bloody hell. 
> 
   I first visited Daventry in about 1963. It is a World Service transmitter
station, with several transmitters running 24 hours a day, each for perhaps
30 minutes at a time on a variety of frequencies, aiming at different areas
in the world. Retuning the all-valve transmitters involved changing tuning
coils, each one sitting on small railway tracks. At the same time someone
had to be standing somewhere in the local countryside ready to unhook the
aerial feeders and move them to the next aerial arrays, aimed at the new
target.
   The standard technique for deciding when it was safe was to hold an
earthed pole near to the feeder. When the arc went out that transmitter was
unpowered, and there would be a minute or so to unhook the cable and carry
it across to the next connection point. The first sign of a problem was
often a phone call from some far-off land to say that they were not
receiving the transmission. That was often followed by a call from a local
phone box asking for directions to get back, or they would have to send out
a search party because their colleague had probably cycled into one of the
local streams in the dark.
   They now have the luxury of power relays to re-route the feeders.

   Standard terrestrial broadcast transmitters are normally powered 24
hours, 7 days a week, so aerial and mast maintenance must be carried out
with the transmitters running, and under all weather conditions. The
effective radiated power is up to about 500KW per channel.


-- 
Chris Bell


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