29 Mar
2017
29 Mar
'17
5:33 p.m.
270K is not a transmission line load.
As I recall ribbon cable is around 100-150 ohms
impedance some place.
The signal does look nice and square.
I doubt is is inductive coupling, with that high a
load, I'd say it was capacitive.
inductive coupling requires current flowing.
Dwight
________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Al Kossow via cctalk
<cctalk at classiccmp.org>
Sent: Wednesday, March 29, 2017 2:35:54 PM
To: cctalk at classiccmp.org
Subject: Re: Cross-talk square-wave?
On 3/29/17 2:14 PM, David Bridgham via cctalk wrote:
And I think this picture is the smoking gun.
http://pdp10.froghouse.org/qsic/pic_24_2.gif
Again, the bottom trace is the CS signal in question and the upper trace
is now one of the QBUS DAL lines (after the bus transceiver and level
converter) that's running across the ribbon cable near the CS signal.
It does appear that induction can make a fairly clean square wave.
simple thing to try is split the ribbon cable between the two signals
