Re: More 'PIDS'

[matthew@mail.usyd.edu.au (Matthew Geier)]

In article <3755EB04.3924CEF3@ozemail.com.au>,
David Johnson  <trainman@ozemail.com.au> wrote:
>Alex Borodin wrote:
>
>> Indeed, I would suggest that the systems in Melbourne and Sydney are prone
>> to EMF not because of the CRT's receiving too much EMF (plasma screens would
>> have a similar problem in that a great enough EMF would cause the phosphor
>> dots to light up and flicker)  but because of the video transmission
>> method.. No, the EMF (even in Sydney or Melbourne) is not great enough to
>> affect a CRT at that distance.
>
>At Como, every time a train goes through, the Television loses reception, and
>the picture turns 5 degrees and changes colour.  It looks like the deflection
>magnets are being turned on the back of the picture tube.

 I suspect maybe the EMF is large enough. Sydney and Melbourne are 'low'
volage DC systems that draw large currents as a matter of course. QR is
high voltage AC. QR fault currents could be less than Sydney running currents.
(I dont know the numbers....)

 The fact that Sydney/Melbourne is DC and not AC probably make the problems
worse, as the repeated fields with same direction of flux probably magnetise
things that should not be magnetised....

 Of course stupid design can make all this worse.... :-)