Our tour first visited the coil room on the upper floor of the transmitter
hall. The vast arrays of copper 'plumbing' were similar to those of Criggion
but in the larger building looked more impressive. All of this was supported on
wooden framing held together with plastic bolts (no ironwork allowed that might
detune the radio performance). The apparatus was built to carry 1000 amps of
radio-frequency current, although it normally operated at 750 amps. The
frequency transmitted was 16kHz normally, although tests had also been made at
22kHz. The transmitter valves operated with an anode voltage of 12 kilovolts,
supplied by some pretty powerful power transformers or else by standby
generators that we saw later in the power hall. Transmissions were normally MSK
(Minimum Shift Keying, a form of FSK-Frequency Shift Keying-used to carry
digital information on a radio carrier) and occasionally A1 (on-off keying or
'OOK').
Some great radio history at these web sites:
http://www.subbrit.org.uk/sb-sites/sites/r/rugby_radio/index2.shtml
http://www.subbrit.org.uk/sb-sites/sites/r/rugby_radio/index70.shtml
I was there several years ago visiting a friend who worked at BT. It was a
beautiful site to see on a clear day...100s of sheep feeding on the grassy
fields under the towers; a massive installation...British TEL actually built
their own towers in those days, had their own repair and maint. shop, crew, et
al.
This installation was significantly larger than our Annapoplis, MD VLF
station. ;-)
73,
dave
wa3gin
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