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Preparing the conductor, part 1

We will use the braided shielding of the 1mm mini-coax.
Therefore we need to peel of the outer sleeve without damaging the copper wires. I advise to use a device similar to the one shown left.
Drill a small hole, the size of the outside diameter of the cable, in a 5 to 10mm thick block.
Attach a scalpel-blade so the point is just slightly over the edge of the hole.
Pull the cable slowly through the hole, thus cutting the sleeve.
Perform some trail runs prior to the real work.

Preparing the conductor part 2

If all is well, the sleeve can be easily removed.
Peel off gently otherwise the cable-part gets all twisted!
Best method is to clamp the wire at both ends while peeling the sleeve off.
After this, get to the inner cable-parts.
With pliers, gently pull it out to get a good grip.
Hold the inner part firmly with one hand.
Separate the two parts by gently rubbing the shielding downwards between your (clean) fingers. The use of cleanroom gloves is strongly recommended.
Each move will separate the parts only a couple of mm's, so be patient.
Be careful not to deform the conductor. The shape must stay hollow, see picture right!
We now have a silver plated copper braid exposed to air. If nothing is done, this will corrode in time. Even if silver oxide is a good conductor, we want to avoid this.

Air-tight assembly of the conductor in the sleeve (1)

The hollow conductor has to be closed at the ends.
Because the sleeve is bigger than the signal-cable, the gap has to be filled.
Both of the above issues are solved using a spiral- wound thin copper wire. Let's call it a "spring".
Use a wire with a diameter equal to the gap between the braid and the sleeve. (D_in - d_out)/2.
Use a small drill, with a diameter equal to the diameter of the conductor, to wind the spring on.
The spring must slide easily over the conductor, but must tight-fit in the sleeve.

Air-tight assembly of the conductor in the sleeve (2)

Slide the "spring" ~ 20mm over one end of the signal cable.
Solder the "spring" with silver solder.
Make sure the solder flows all the way through to the center to make the cable air-tight.
Also make sure that the solder leaves a smooth surface.
Insert the one-side prepared cable into the sleeve.
With pliers, insert also the soldered spring into the sleeve. This must be a tight-fit to make it air-tight. If not, make a spring from ticker wire.
Mount a spring at the other end of the cable. Solder it very close to the sleeve. Insert this also in to the sleeve.
The signal-cable will touch the sleeve only at some incidental points which is part of the concept.