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Folded up (folding up) the coax on (Tek) probes: not good, right?


Greg Muir
 

Put some similar coax that has been treated this way on a TDR or DTF network analyzer and observe the little reflection bumps at the sharp bends. May not be significant enough for the average probe user but as you progress towards microwave those little bumps become bigger ones.

I had an instance where some coax had been removed from a project and the tech zig-zagged and folded it up in a very tidy and small bundle securing it with a Ty-wrap (total no-no). Over a considerable time the inner dielectric cold flowed just enough to allow the center conductor to move towards the shield resulting in it being dumpster food..

When I receive any cables that have been treated that way I place them in a warm oven to slightly soften the dielectrics then lay them out straight on the floor to allow them to cool. Of course anything attached to the ends does not enter the oven. The most chronic are the IEC power cords that have been bound up so tight by someone that they never straighten out by themselves. Then after cooling they are coiled up the same way a cowboy coils his ropes.

Greg


John Brown
 

My eBay success with vintage Tek probes is around 2/3 overall. I'm inclined anymore to lean toward new Probemasters equivalents. Maybe I'm not discerning and/or knowledgeable enough to participate in eBay probes. Can't say any have been misrepresented by the sellers. They're just - umm - vintage.

--
W0MPM John


Jean-Paul
 

Roy: The coax of probes is specially designed for a certain Zo and bandwidth. The small diameter means special dielectric and wire design.

Wideband probes eg 500 MHz...over 1 GHZ are degraded by tight bends or even kinks and must be treated carefully.

Most ebay sellers this its just a wire and wrap tightly. Have seen damaged BNC, bent probe tips and wrong ground wires and prob hats.

I try to buy ebay probes only id the seller is aware of this, and can pack properly. BEWARE!

Good luck,

Jon


Ed Breya
 

Yes, too tight a radius bend, pinching, folding, etc are bad for probe leads. It's probably safe to assume that many leads, even if not pictured in such conditions, may have been abused at some point, so you never know for sure the condition they are in.

Ed


snapdiode
 

It's a very thin center conductor.


Tom Lee
 

It's probably not nearly as bad as you fear unless the cinching is so extreme that the dielectric gets pinched to the point of permanent deformation. Anything's possible, of course, but twist ties and standard-issue humans don't ordinarily do that.

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 11/2/2020 17:08, Roy Thistle wrote:
High All:
Ever seen Tek probes for sale on the bay?... where the probe's coax has been bundled up...like you used to bundle up a piece of very flexible rope, back in Boy Scouts... or the coax is folded round and round, in a coil... then all squished together, at the middle... and a twist tie, elastic band, or tie wrap...fitted around.
What's behind that?
That can't be good for the coax... do you think? ... especially, high-frequency probes.
Regards.
Roy




Roy Thistle
 

High All:
Ever seen Tek probes for sale on the bay?... where the probe's coax has been bundled up...like you used to bundle up a piece of very flexible rope, back in Boy Scouts... or the coax is folded round and round, in a coil... then all squished together, at the middle... and a twist tie, elastic band, or tie wrap...fitted around.
What's behind that?
That can't be good for the coax... do you think? ... especially, high-frequency probes.
Regards.
Roy