The following is purely fyi for those that understand...
...TDR measurement equipment.
Just out of curiosity, I measured some RG142 / 50 ohm coax, and some RG59 C/U 50 ohm coax. Both showed 50 ohm z.
Then I "measured" some of our mil spec shielded wire. Here is what I measured:
Single conductor shielded (as used for P leads)...15 ohm, very flat, very consistant.
Two conductor shielded...one conductor to shield = 22 ohm. Differential, conductor-to-conductor,
single ended = 35 ohm. Very flat, very consistant.
Three conductor shielded (as in audio phone jacks, mic jacks)...just measured one conductor to shield = 28 ohm and extremely flat trace.
My conclusions for this shielded mil spec wire is that it is very high quality and exhibits a very uniform impedance. If we ever needed a "coax" cable with a low impedance (15, 22, 35, 28 ohm), then this shielded cable would work quite well.
Now, back to the subject of this thread...if the manufacturer is calling out that both ends of the braid of this shielded cable (don't call it coax) should be attached to gnd, then by all means follow the suggestions. The design point and implementation called out may have nothing to do with single ended driver / receiver circuits and the techniques used to minimize the potential for noise reduction. It may just be a requirement of the specific equipment that is being attached...