In a message dated 25/07/00 03:40:20 GMT Daylight Time, 
John.Tacinelli@........ writes:

> My problem is that at 8:45 PM every night I get a sudden increase (or 
> decrease) in voltage through my amplifier that causes the trace to move off 
> to the right hand side of the screen.  It stays there until 5:45 every 
> morning.  Then it goes right back.  The seismograph itself doesn't seem to 
> move.  I have run it on an uninterruptible power supply and it still does 
it. 
> I watched it happen tonight and I could detect no environmental change in 
> the area of the seismograph. 
    
    With the alternative PSU not changing things, it sounds more like a RFI 
problem. Does your utility company control the times at which it supplies low 
cost electricity and how does it do it? Does it use low level RF on the line 
/ is there any other service which corresponds to these times? Do any 
companies read meters using pulses / RF on the supply? Does a loop aerial and 
a diode pick up anything? Does a radio tuned off station pick up anything? 
Have a look with a 'scope and see if there is interference coming through the 
supply during the night? Is there any heavy industry locally which uses night 
time power and feeds spikes onto the line? Is there any power used for 
heating or similar purposes in the building? Can you run on batteries for an 
hour and turn off the building / floor supply entirely?  Last thought - I 
notice the .edu - could some young genius be playing a practical joke? With a 
time clock? 

    Regards,

    Chris Chapman
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