FW: [Malvern] Electrical Intreference

[Ian Pascoe]

Hi Steve

OK, that all makes sense.

Rather intrigued about the in line filtering before the distribution panel
in your home.

If one of these were in place, would it be safe to presume that the amount
of RF captured by induction within the house is neglible or should things
like PCs audio systems etc still have their own RF filtering?

Ian

-----Original Message-----
From: malvern-bounces at mailman.lug.org.uk
[mailto:malvern-bounces at mailman.lug.org.uk]On Behalf Of Steve Cashmore
Sent: 28 January 2007 14:23
To: Malvern at mailman.lug.org.uk
Subject: Re: [Malvern] Electrical Intreference


Hi Ian,

Ian Pascoe wrote:
> For any sensitive electrical equipment it is generally recommended to have
> an RF filter somewhere on the mains feed to remove spikes that come in
over
> the mains power.
>
> If you are converting from AC to DC power will these spikes still be there
> after the conversion?
>
> If you transform the power down from 240v AC to say 12v AC does the spikes
> decrease in line with the reduction or do they stay the same?

Unfortunately fast rise-time spikes tend to capacitively couple their
energy directly to the output through components of the conversion
circuitry such as a transformer.  For that reason it's hard to predict
exactly what reduction there may be for a given circuit. It has much to
do with the physical construction of transformers and assembly of the
final product.

> And lastly, I have read that if a neighbour uses the mains ring to provide
> data transfer for either audio or computer networks, that extra
information
> leaks back out into the mains distribution.  Would an RF filter remove it
or
> do you need something else?

Yes, an RF filter will remove the data modulation from external
radiation through the mains network.  Without such a filter, a reduced
signal may be present up to the transformer sub-station.  There are such
commercial domestic filters available although I can't point to a
specific example.  Some clip-on across the incoming house wiring making
no electrical connection, but have limited filtering, and others are
physically wired at the distribution board and provide a high degree of
isolation.

Schaffner are a well known manufacturer of filtering devices in Europe.
  In the USA these RF filters are often available from whole house
remote control equipment suppliers.  Many of these systems use a low
frequency RF modulation on the house wiring for control purposes.

best regards,


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