RE: advice needed for weak signals and noise

["Keith Doxey" <ukha@xxxxxxx>]

Hi Joe,

Electrical noise is unlikely to be a problem. Nut the equipment you list is
likely to be!

Since the introduction of the EMC regulations several years ago
manufacturers have had to make equipment that does not chuck noise out onto
the mains. The quick and easy fix for this is for them to fit chokes inline
with the mains lead.

This stops most interference from entering or leaving the equipment.
Because
a small amount of noise will still get through, they then fit a capacitor
across the Live and Neutral on the mains side of the chokes to short
circuit
any residual interference.

The filter is very good at stopping the interference from leaving the
equipment, but unfortunately a side effect of this is that any other noise
on the mains is also killed. In most cases this would be a bonus, but as
X10
(or any other powerline carrier) is essentially interference that is
deliberately introduced onto the powerline, it also gets killed or
attenuated.

The weak signals you describe are exactly that, something further down the
powerline is sucking up loads of signal reducing its strength.

The devices you suspect of causing interference are actually the things
that
are sucking up the signal. Removing them allows X10 signals to propogate
successfully so the outward appearance is that you have "removed the
interference".

What you need are filters designed to stop interference getting INTO
equipment. These consist of chokes at the mains side and a capacitor at the
equipment side. Fitting these to a distribution board allows to you to stop
several devices from killing the signals with a single filter.

Because chokes are quite large and heavy. the filters also tend to be quite
large, similar to large plugtop power supplies. Some of the
"Filtered"
plugboards will actually make matters worse. These do not have the physical
space to accomodate the chokes required for proper filtering and tend to
only contain Capacitors to short out interference (including the desired
X10) and Transient suppressors to remove spikes.

I keep meaning to delve into the depths of my garage where I have some old
choke type filters so that I can test them out. They are available in 3A,
7A
and 13A versions so could easily filter a whole rack of equipment.

I have just looked at the Farnell website and was shocked to find out how
much they actually cost. ( I used to fit hundreds of these!!!!)  The specs
and prices are listed below...

Filter 	Attenuation
Rating  	100kHz  1MHz  10MHz

3A		40dB  70dB  60dB
7A  		50dB  50dB  65dB
13A  		20dB  50dB  60dB

They are available in two styles, a wireable plug, or a plug in adapter

Adapter Style		Wireable Plug Style
3A	150219	32.44		151317	28.36
7A  	150220	39.62		151318	32.95
13A  	151030	47.61		151319	44.00

As I said, I havent actually tried one to see if it does stop devices
killing X10 so please dont rush out and order a load until after I have
been
rescued from the pile of crap^H^H^H^H stuff that will one day be useful
that
fills my garage.

Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: jmj050856 [mailto:jmj050856@xxxxxxx]
>
> I have recently entered the world of X10 and despite many frustrated
> days and nights (I've even resorted to reading the instruction
> manual) I still can't get things working. I have identified 2 main
> problems though, so really what I need is some advice on how to
> correct them.
>
> 1) weak signals -
>
> 2) electrical noise -