[Gb-ccb] forwarded message from Martin Shepherd

[Martin Shepherd]

>  > On Wed, 20 Aug 2003, John Ford wrote:
>  > > Martin, don't forget about the RFI filters that will be in the line.
>  > > they will change your numbers somewhat.

Indeed. The 32MHz Pi-filtered DB25 socket that Spectrum Control sells,
has a 100pF shunt capacitance. That unfortunately makes it impossible
to arrange for a frequency-independent match over the frequencies of
interest. I'll try to figure out how significant the resulting
frequency dependent reflections would be on a 100ns rise-time
step-function, and if need be, change the matching resistors to move
the frequency of the perfect impedance-match away from DC.

> No, they are still necessary to filter the lines out of the box.
> *every* line in and out of the box must be filtered.

Sorry, I guess that you have said this before. I wasn't thinking.

Martin