[sdiy] 100 MHz EMI, what can it be?

[Czech Martin]

Yes, compared to a three phase current power line the single phase
overhead contact line has more radiation, I think.
The three phase system will average to 0 very soon, if some distance
is between the line and the measuring point. This is not the case
in the single line railway case.
The rails and the line are ca. 5m away, and near to ground.
This makes a pretty loop. It is 15kV and about 600 A. 
Most engines today use SCR techniques, i.e. higher frequency noise.

I can see that the electrons in CRTs start to wobble if a train comes
near, even if I can still not hear or see the train. About 1 min
in advance.

I also found that the older polar heart rate measurements systems
stopped working if you ride allong railway tracks, at least to a distance of 
50m or so.

m.c.

-----Original Message-----
From: jhaible [mailto:jhaible at debitel.net]
Sent: Montag, 14. April 2003 20:12
To: Czech Martin; Magnus Danielson
Cc: uzs159 at uni-bonn.de; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] 100 MHz EMI, what can it be?


> > Anyway, I'm a good candidate for a "banana, XLR, telephone plug,
shielded or
> > not shielded, balanced or not balanced measurement comparison".
> > The air is full of RF, the railway will add 16 2/3 Hz power line noise
and
> > magnetic fields to that. Could you ask for more for such a test? ;->

AFAIK railways are an exception to the usual EMI regulations. Whether they
are legal exceptions I don't know. But no one can possibly just close down
the Deutsche Bahn because it violates EMI rules so blatantly.
Imagine the magnetic fields just from getting the current from the
conductors
above the wagons down to the motors. 16 Hz if there wouldn't be any
intermittent
contact. In practice, wide band noise. It's possible that there are fixed
frequencies
for communications, too, but I don't know the details.

JH.