Re: [RFI] NOISE GADGETS

[David Jordan <wa3gin@erols.com>]

I agree with Tom...his experience is that power line filters he has 
tested make poor RFI fitlers.  That is a fact of his experience.

My experience is different and I've been working in telco long before 
the Internet and PCs when there was just one phone company...

But I have to tell ya Tom, my ISDN circuit ran error free with numerous 
"power line" filters installed.

My conncection in the country is over 8 miles from the CO, all analog to 
the switch.  I consistantly get 28.8kbps connections, better than any of 
 my neighbors and yup, you guessed it, I've got a power line filter in 
the line.

I'm just sharing my experience with the reflector Tom.

73,
dave
wa3gin

Tom Rauch wrote:

> > > The impedance of the wires has almost nothing to do with
>
> the
>
> > > design impedance of the system, because the wires are not
> > > large fractions of a wavelength long. The critical
>
> parameter
>
> > > is the source and load impedance. In a short line,
>
> standing
>
> > > waves have no place to stand.
> >
> > In a central office or studio, that's absolutely true. But
>
> if I'm miles of wire
>
> > from the central office it isn't.
>
>
> Central offices have little to do with it Jim.
>
> The signal is often in digital form over copper pairs, and
> is converted to analog at an equipment cluster near a
> distribution point. You can be 20 miles from the central
> office and have a 50-foot long analog pair, and your view of
> life will be that of someone 50 ft from the central office
> (unless you do a ping and echo test).
>
> My specific points in this are:
>
> 1.) Telephone systems are designed to be 600 ohms.
>
> 2.) It is impossible to predict characteristics of random
> power line filters, and how those filters will affect random
> systems
>
> 3.) Ability to survive poor balance and improper loading
> depends on what you run through the line and how far you are
> from the D/A conversion, which is almost NEVER at the
> central office.
>
> 4.) My experience, and I work on this stuff every week, is
> that power line filters make very poor telco RFI filters
>
> I can't add anything else to this topic.
>
> 73 Tom
>
>
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