[time-nuts] Coax Connectors (was Re: Opera coordinator has resigned)

Magnus Danielson magnus at rubidium.dyndns.org
Sat Mar 31 22:13:25 UTC 2012


On 03/31/2012 10:08 PM, Javier Serrano wrote:
> On Sat, Mar 31, 2012 at 9:24 PM, Achim Vollhardt<avollhar at physik.uzh.ch>  wrote:
>> I do work in high energy physics and we use LEMO and other standards. For
>> some years now, I have started to advertise against LEMO (in particular the
>> LEMO 00 size), as it is VERY sensitive to mechanical defects and partial
>> connection (yes, you can ..). We have found very often defective LEMO
>> connections, which could only be detected via time domain reflectometry. Or
>> LEMO interfaces, which changed impedance significantly when rotating them in
>> the fully mated position.. this list could be extended a lot more. And this
>> famous click when mating is inaudible in typical high energy physics
>> electronics barracks.. too much fan noise.
>>
>> In addition, for the very fast signals of modern DAQ systems, LEMO 00 is
>> just not up to speed (literally) anymore. If size is not of ultimate
>> importance, we switched to SMA, or SMC if size matters.
>
> I am very interested in this, since we just decided to use LEMO 00
> over SMC in some of our designs:
> http://www.ohwr.org/projects/fmc-projects/wiki/SMC_vs_LEMO
> This is for ~100MHz work, so bandwidth was not an issue. Compatibility
> with legacy was the major criterion in our case.
> I would be interested in reading what people are using as coax
> connectors in space-constrained environments like FMC, and why.

You should have included SMB in that comparison. It would have been a 
closer match to the LEMO 00.

Cheers,
Magnus



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