Vasco GuitaComparison between SMC and LEMO 00 connectors
Two types of high-frequency, coaxial connectors can be used on FMC cards: SMC or "LEMO" connectors. Each of them has advantages and disadvantages that are compared on this page.
| Feature | SMC | LEMO |
|---|---|---|
 |
 |
|
| Standard | MIL-C-39012/73/78 (1960's) | NIM-CAMAC CD/N549 (1970's) |
| Wikipedia | SMC on Wikipedia | LEMO 00 on Wikipedia |
| PCB 90 degree bent socket | Chin Nan 26-10-5-TGG Johnson 131-6701-341 (types that fit FMC) |
LEMO EPL.00.250.NTN FISCHER DPL 101 A004-14 HUBER-SUHNER 85 QLA 01-0-3 |
| CERN usage | RF group (also SMA) | general usage, available from Stores |
| CERN purchasing: PCB bent socket | not available from CERN Stores | CERN Stores 09.46.11.180.6 |
| CERN purchasing: Cables | not available from CERN Stores | many lengths 04.69.11.A |
| Price | A (1000 pieces) | 2.7 x A (CERN stores) |
| Size | fits FMC | fits FMC |
| PCB footprint | Similar, but hole sizes differ and need other drilling | |
| Diameter Gnd pins (4) | 1.7mm | 0.7mm |
| Diameter Signal pin (1) | 1.2mm | 0.5mm |
| Max. frequency | 10 GHz | LEMO catalog: 4 GHz (10 GHz stores spec.) |
| Accessories | T, SMA to SMC no SMC-LEMO adapters |
50 Ohm termination, T, I, BNC&CINCH adapters, ... |
| Tools needed | Needs dedicated spanning tool as connectors are tight on FMC cards. (CERN specific design) |
No tools needed (push-pull) |
Text from the LEMO 00 NIM-CAMAC & 01 COAXIAL CONNECTORS
catalog:
LEMO coaxial 00 and 01 Series (50Ω)
Fundamental research in particle physics as practised within CERN and
other nuclear research establishments requires more and more complex
equipment of high performance in order to achieve the objectives. The
needs of such research contribute to the development of leading products
for the whole of industry. For many years LEMO has participated in this
evolution. This has resulted in a range of miniature coaxial connectors
(50 Ω) with a push-pull self-latching system, the LEMO 00.250 series.
These connectors now form the basis of the NIM-CAMAC CD/N 549 standard.
From an RF expert: "a SMC, SMA, N, or any other threaded connector has an advantage over snap or bayonet connectors (LEMO, BNC, etc) for the phase stability of the connection. This is simply due to the mechanical properties of the connection. This really matters at high frequency, maybe not such a big deal below 1 GHz. As an example the phase budget for our LLRF system is 0.1 deg at 3 GHz. This is about 20 um (micro-meters) there is no way that a LEMO connection is stable to that length in the presence of vibrations or other mechanical stress."
Update 30 May 2011: CERN decided to use the LEMO 00 connector on the FMC mezzanines developed for OHR. The main reasons are: there is a large installed base; there are more accessoires; the connectors are more easy to remove in tightly dense environments (like on the FMC).
Update 5 May 2017: See also FMC Components, where other through-hole SMA connectors compatible to LEMO are mentioned.
Update 21 April 2023: after a remark on the cern-electronics mailing list, some thoughts about LEMO vs threaded connectors were shared within BE-CEM. While we notice the use of threaded connectors for RF, we do not really have issues with LEMO for the signals we carry. Furthermore, we are indeed, in a way, stuck with LEMO, given the number of boards in our catalogue using it. The handling of dense installations is as well much more practical with LEMO connectors.
Erik van der Bij - 21 April 2023