Don't buy SMA cable assemblies from CentricRF

[Smoky]

Just looking at the few samples of SMA ends in the pictures reveals differences all across the map. Thick walls, thin walls, stepped and non-stepped contacts, loose dielectrics, tight dielectrics. Now bring in all of the differences that can be found in the receptacles 

[joeqsmith]

Just looking at the few samples of SMA ends in the pictures reveals differences all across the map. Thick walls, thin walls, stepped and non-stepped contacts, loose dielectrics, tight dielectrics. Now bring in all of the differences that can be found in the receptacles 

Which is why I asked early on about if their gage could even measure their particular connectors, why I wanted to see what they looked like and why I posted about mixing the 3.5mm and SMA gages.   

Again, I have no way to know if there was a problem with the OPs measurements or not.  This is also why I had suggested an independent repeating the measurements. 

I could measure three of the eight I show with confidence that we would get something meaningful.  One that has no step.  Four with some sort of step that I doubt I could tell you anything more useful with a gage than what the photo shows.   It doesn't mean those connectors are bad but that I just can't measure them.   


A simple experiment.   I blow out the gages and zero both the pin contact and dielectric gages to the master gage.   Next measure the Digi-key cable which does not have a step.  I would expect both gages to measure from the reference plane to the dielectric.  All measurements in inches.   

Connector 1,  Dielectric 0.0045,  Pin 0.0045
Connector 2,  Dielectric 0.002,  Pin 0.002

While it meets the industry standard, it is a bit high.  The real point of this exorcise is that the two measurements basically match.

Measuring the pin of the cable I use for my X-band EPR experiments,
Connector 1, Pin 0.0025
Connector 2, Pin 0.0005
Very nice.       

Let's try the home made cable for my HP8754A.   
Connector 1, Pin 0.003 

And finally my Gore cable.   
Connector 1, Pin 0.003 
****
I checked the Gore cables dielectric and then using my 3.5mm gage, I remeasured the Pin and get 0.002875 (basically a half division off).  Consider that was a completely different master used to zero this gage, I think it's pretty safe to say we are in the ballpark. 

It seems pointless to attempt to measure the other SMAs as I have zero confidence in what the gages would show.   

[joeqsmith]

I wouldn't suggest that adapters are immune.  To conduct that T-Check experiment, I purchased some very low cost Tees.   I think I paid something like $10 for a 4 pack.  Guessing you could get these even cheaper but I picked them up off Amazon. 

Notice the pins transition to the step has a fairly dramatic radius.   Measuring the pins location:

Connector 1, Pin -0.0005
Connector 2, Pin -0.0015

I had tested this adapter using my Agilent VNA with good results to 9GHz.   There are no detectable signs where it touched off on the female pins.   Measuring one of the sacrificial adapters I used, the female pin is recessed 0.0025 providing enough clearance. 

Two wrongs don't make a right but it certainly can help.

[joeqsmith]

Showing SMA used on the cables supplied with the NanoVNA H4.   Once again, we do not see flat step.   The step is far below the dielectric but note the tip of the pin. 

Again, the pin depth of this cable could not be measured with my gages. 

[joeqsmith]

Image from an ebay ad for a new cable. 

https://www.ebay.com/itm/126457563736

[joeqsmith]

Had to make up a custom cable today.   The coax's center conductor is used to form the SMA's pin.  No step.  Showing the dielectric and contact. 

This is where the threaded gage set would be nice to have.   

[joeqsmith]

...
Reputable" manufacturers are selling SMA cable assemblies with pin protrusion. This practice seems to be quite common in my admittedly limited sample. I'm directly calling out CentricRF (Centric RF) in the title since I had some discouraging communication with them (more on this below), but I've also experienced the same problem with Mini-Circuits and Crystek.
...

My friend Flipper is shipping out several Mini-Circuits cables but in the mean time, I thought I would have a look at a few that I have on-hand.  You can see these have a flat step, unlike many of the low end cables I have shown in this thread.  These can easily be gaged.   I checked all of the connectors and none of these have protrusion.   

CentricRF never did respond to my offer to independently gage their products.  I am still not convinced that the OP was new to this topic, bought a used gage without a standard and this was their first time using it.  I would have liked to have seen what the pin looks like to see if it was some sort of compatibility problem.   Why not disclose all the details if your going to blast a company for their quality?   Call me cynical,  but I have a lack of trust to much of what gets posted, especially when there is so little data to back it up.   

[joeqsmith]

The Mini-Circuits cables my friend provided are semi-ridged stepless.   Similar to the one I recently made.   I measured 10 connectors pin and dielectric.   All were in spec.

I have checked a total of 16 Mini-Circuits , and 4 Digi-Key custom cable connectors so far without any issues.  So far the only sign of protrusion I have seen was with those really low cost Tees.   

[joeqsmith]

I bought a couple more cables from Mini-Circuits through Digikey.   These are a PN 086-6SM+

https://www.minicircuits.com/WebStore/dashboard.html?model=086-6SM%2B.

These use a stepless contact. 

[joeqsmith]

.... and 3/4 minicircuits cables showed pin protrusion on at least one connector (up to about 4 mil). ....

Testing another new cable from Mini-Circuits.

[joeqsmith]

They spec the insertion loss for this cable to be 1.8 to 3.8dB from DC-6GHz.  Just normalizing the LiteVNA64 from 300k to 6G, measures better than 3.1dB loss (connectors properly torqued).   These cost about $150.  So not a very expensive cable and seems to meet spec.   While OP may consider Mini-Circuits as a bad supplier, it's not been my experience.

https://minicircuits.com/WebStore/dashboard.html?model=CBL-10FT-SMSM%2B