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Old May 26th 07, 08:59 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: Jul 2006
Posts: 285
Default A different way to reduce common mode noise,

On May 26, 7:27 pm, Telamon
wrote:
In article . com,

wrote:

The incoming AC mains power is bypassed with
parallel 0.01uF and 0.001uF(1000pF) 2KV low
inductance capacitor. We also have a "whole house"
over voltage clamp at the breaker panel.


Every light switch has a 0.001uF cap across the
contacts.


Snip

You should only use specially rated capacitors for this type of
application. You understand that a capacitor on the mains supply draws
current to heat the dielectric as a consequence right?

You should also have a fuse of circuit breaker between it and the mains
supply in case it shorts. The lamp cord is not rated to what the house
circuit breaker rated at of course.

Here is the skinny on the subject.
http://my.execpc.com/~endlr/line-filter.html

He also describes a snubber network, a series resistor and capacitor
that is a good way of suppressing switch noise from rectifying diodes in
power supplies. The diode switch noise on power supply DC outputs causes
the hum on portable radios.

--
Telamon
Ventura, California


The caps in the breaker box have 1A fuses in series for protection.

The caps in the light switches have 10 ohm, 1/10W, metal film
resistors.

And yea I used the correct caps, I would hate to burn our home down.
My wife would be mildly miffed.

I am writing up a piece discribing my experiences at home and at
another house
detailing the positive effects the Topaz ultra-isolation. It is too
bad there is no
simple way to build broad band RF isolation transformers with less
then .5pF
capacitance between the primary and secondary.

Isolation of at least 10K is needed to knock common mode RFI down low
enough
to not be a problem. The trouble wil going with series inductance on
the shield, or
even harder, balanced feedline is the interwinding capactance allows
the noise to
sneak past.

Terry

Terry

 
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