Re: Filters - Quality


"Eeyore" <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote in message
news:4652DC01.AF56A63D@xxxxxxxxxxxxxx


JohnW wrote:

Now comes the problems...

Any filter is designed to work best in a known environment.
In telecomms, we practically have a 600ohm balanced
transmission line environment, so this (balanced, 600ohm) is
used in the design to ensure the filters work as required.

Here's the next problem. The characteristic impedance of the
telephone cables
to the home is actually about 100 ohms !

Did you mean 1000 ohms? When I worked in a Telephone Repeater Station,
a '1200 Line 600 Office' transformer matched a customer line to
transmission equipment quite well - a through to term dip close to the
nominal 3.5 on a dB meter on the Office side confirmed this.

Martin


.

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