Re: Filter problem

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

[...]VNA. 

 
Perhaps a quarter-wave line could be used as part of  the impedance
transformation?  Audio screened cable has a characteristic impedance of
about 120 ohms, so a termination of 50 ohms at the outpute end of a
quarter wavelength would appear as 288 ohms at the input end.
 

You don’t want much conductance at the open end. Just the featureless cut
end.

I wasn't thinking of using that line as part of the filter.  The
equipment is modular, so there have to be connecting leads between the
various parts.  My idea was that by using 120-ohm cable and cutting it
to the right length, the transformation could be done in two steps; line
and transformer.   This would alow a large impedance ratio to be
obtained whilst keeping the ferrite transformer ratio to a sensible
value.

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk