Message-ID: <C6ABA8DEC115D311A29D00105ABD3264A96BEF@nmex01nt.hsd.utc.com>
From: "Soegiono, Gamal" <soegiono@nm.hsd.utc.com>
To: rsgb_lf_group@blacksheep.org
Subject: LF: Mains Borne Noise
Date: Tue, 23 Jan 2001 11:44:33 +0100
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>> Has anybody on the list got a "whole house" mains filter 
>> installed at their QTH?

Not a "whole house" mains filter, but a radio room
mains "filter".

All main supply to my radio equipment is run via a
single phase isolation transformer, having two shields.
Thereby my radio equipment does not have any electrical
continuity with the phase conductor, the return conductor
and the protective conductor. In order to guarantee
safety, I drove a separate grounding rod (9m deep) into
garden ground close to the house and use this as my
"private" safety conductor.

The isolation transformer has its primary windings
shielded and its secondary shielded individually.

I do connect the primary shield with the "normal" house
safety conductor, the secondary shield with my "private" 
safety conductor.

As the secondary winding is split (to allow for 120/240
adaptation) I connect the center tap to the "private" 
safety conductor as well. Thereby my "private" mains
becomes symmetrically in respect to my private ground.


In your case, designing and constructing a whole house
wiring, I would recommend to consider the following
points:

(1) you want to prevent conducted noise, coming along
the house mains entrance, creep into your house mains
distribution system (wiring) and distribute therein at
will.

(2) you operate several equipment being potential
sources of mains noise (any equipment utilizing SMPS,
uP control, SCR dimmers and the like). You maybe will
be interested to prevent home made mains noise from
distributing in your house mains distribution 
system (wiring).


To prevent (1), you may use 3 single phase isolation
transformers, or 1 triple-phase isolation transformer
right after the electric meter.

To prevent (2) you need to run your mains wiring in
separated cables to the destinations. One cable for
living room, one cable for kitchen, one cable for ...
This is a minimum measure.

Additionally you may put electical filters in each
of those cables. Thereby you prevent distribution
of mains noise from one room into the other.

If you just want to have a clean mains supply for 
your radio room, you may perhaps adopt my solution
described above.

To speak about "mains noise" is somewhat unspecific,
as there are several ways how noise may distribute
and what frequency range is concerned.

One way, how conducted noise can propagate in mains
cables is, running in the phase conductor and returning
in the neutral return conductor. Academically, the
safety conductor is not involved. This is called
differential mode of propagation.

The other way of propagation is, conducted noise flows
in both the phase conductor as well as the neutral return
conductor in the same direction. Now the return path is
the safety conductor. This is called the common mode
of propagation.

My a.m. isolation transformer is excelent in supressing
the common mode propagation over a large range of
frequencies. It is still effective for higher frequencies
to suppress differential mode of propagation (approx.
starting at 500 kHz). To increase suppression of 
differential mode noise, I intend to add differential
mode chokes (inductors) plus capacitors from phase
conductor to neutral return conductor at the primary
side of my isolation transformer.

Just some ideas which hopefuly are of some benefit.

73 de Gamal