Voltage surges, was Re: [Gllug] Swapping SW RAID 1 disks from PC to Sun
chrisbell at overview.demon.co.uk
Sat Aug 14 12:03:38 UTC 2004
On Sat 14 Aug, Christopher Hunter wrote:
> My setup has outdoor aerials, feeding tuners in a diecast case outside the
> house, which then provide optical fibre connection indoors, with another
> fibre being used for control from indoors.
Off the shelf tuners? How was the output connected to the fibre? It
sounds as though you were using either professional or home-made equipment,
not the usual kinds of retail hardware.
BBC standard OB policy was to always use an earth spike on every
individual vehicle, scaffolding, etc. Unfortunately in practise it is not
always possible to dig up the tarmac or concrete, and even the nearest drain
only conducts as far as the U-bend, so the earth spike was often placed
under a vehicle tyre. We did not always have a choice of parking positions,
and we did not normally carry very long earth cables for every vehicle. Any
additional cables should be ordered by the engineering manager for each
individual programme, if they remembered.
The mains supply to most vehicles was via either 100amp or later 63amp
cables, and the return earth loop was always tested to comply with minimum
regulations, but often came from a generator with the best earthing
arrangement that we could manage at the time.
Cable termination panels were connected to the vehicle chassis, most
cables had a chassis earth connection and connectors with a metal outer so
picked up random earths along their routes (although this could be more of a
problem because of random mains hum).
Despite all this we had very few real problems caused by lightning,
although a later rule was that staff should retreat from high places when it
was known that lightning was expected.
Some years ago a comms engineer received no more than a fright when he
was panning a receiving aerial on top of a 100 foot Simon Hoist at the start
of The Boat Race; the hoist was hit by a single unexpected lightning strike.
There was no damage, the hoist was brought down, the engineer dragged off
and left with the local St John's Ambulance team to recover, while he was
replaced by another to cover the race.
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