I picked up a few feet of Belden 8719 instead, is there any point in me connecting the guard lead on to the shield most of the units I would be testing don't have a guard for eg 34401As
Belden 8219 has Tinned Copper Conductor and it is stranded. I have three of the Fluke Low Thermal cables 5440A-7002 from different sources. One was made with Belden 8240, and the other two were made with Intercomp P/N 2482A. All three say RG-58/U (solid bare copper conductor) on them. So to try to reproduce the Fluke original I purchased JSC Wire & Cable RG-58/U instead of the Belden, but it is equivalent to the Belden 8240. I then found some so called "Gold Plated" Banana plugs that have a screw to connect the center conductor and allow the RG-58/U center conductor to enter from the end rather than from the side as in the Pomona 5406 which is made from gold plated beryllium copper which is hopefully "low thermal". While Pomona doesn't state that the 5406 is low thermal some simple experiments seem to indicate they are. Yes, the Fluke leads are two parallel RG-58/U coax cables with the blue third lead hooked to the shield of both cables. So I made up a reasonable copy of what Fluke had done with the unknown manufacturer's banana plugs. They appeared to be gold plated so I bought them. I have no idea what the body is made from or what the spring is made from. It could be beryllium copper as they have worked well for a few years without loosing their "springiness" so to speak.
See the attached pictures of what I have done. 1819 is the original Fluke cable, 1817 is my imitation of what Fluke has done (with my unknown banana plugs on the ends). 1962 has the Pomona 5406 on the left with two of my unknown manufacturer on the right, one assembled and one disassembled (1963 is a closer view). The unknown also has a hole where a banana plug can be inserted from the side for an additional cable if necessary. The screw then clamps the center conductor of the RG-58/U securely to the plug without soldering. I allow three minutes after insertion before making a measurement to allow any thermals to dissipate. I still need to find a good way to measure the thermal effects of this. One crude way is to just plug the cables in and then put my fingers on the plug/jack combination and see what effect this has at the input to my HP 3458A. I do know that the Fluke does NOT react much to this "test", at least at the sub microvolt level. Right now this seems to work ok for me.
Bill