super-accurate coax cable cutting

[Bob Minchin]

I'm guessing that this might be a cable set for a network analyser? If so you can usually normalise the leads before inserting the unknown network.

[John Rumm]

You may find that you can use the plugs to adjust the effective length anyway. Even aspects such as how far the coax inner penetrates the cup on the pin are going to make a difference. You would have to be making live measurements as you add the final termination.

I suppose you possibly could even use "stretch" as a final calibration - i.e. mechanically alter the length once the cable is made up.

[Ian Jackson]

This is exactly what I have been thinking for some time. It's a while since I used any modern sophisticated electronic test equipment in earnest, but where necessary, there's often an immediate pre-test normalisation facility.

If the OP is trying to carry out a 'normal' test procedure, and what he thinks he needs to do is impossible, then probably either it is not a 'normal' test procedure, or he isn't doing what he should be doing. Would an RTFM help?

[Bruno]

Which isn't really practicable AFAICS.

Not feasible. There's a certain amount of elasticity in these cables so even if it were do-able to the required tolerance, it wouldn't hold.

I think I'm now beginning to see why the manufacturers charge a small fortune for these sets. There's no alternative to proprietary lead sets

- unless one is dealing with low radio frequencies of course where lead length variations are far less significant.

[jrwalliker]

As I mentioned in an earlier post, the VNA may use fairly ordinary coax inside. My HP 8753A 300kHz to 3GHz VNA certainly does.

I made up my own cables from the VNA to the T/R test set using rg402 coax and soldered on N connectors with very good results.

This is less of a problem than you think.

John

[Tim+]

I'll freely admit to knowing nothing about stuff like this but I see that some N connectors "screw" onto the cable like F-plugs. Could the screw be used to "fine tune" the cables?

Tim

[The Natural Philosopher]

ADFAICR that was essentially how we tuned phased delays on radar sets 'back in the day'.

[Bruno]

I wish! I do possess a suitable stereoscope, but your technique also requires a steady hand and a good eye and unfortunately I've got neither. :(