I would like to connect an external UMTS antenna to the module, because of this I need a 15m long cable. The antenna has N-connector and I have to decide which connector should I put in the other side of the cable. I found only SMB connectors(Bulgin) which rating is IP67. The rating is important because the antenna is connected to an outdoor measurement system. Does it has any disadvantage of this connector in the 1800-2200Mhz frequency range?

I have the following concept:

N(antenna)--------------SMB(IP67, connection to the box)------SMA(Module)


The principal difference is the major one:

• SMB connectors are Snap-In. You push them together to mate, and pull them apart to unmate.
• SMA connectors are threaded. You have to screw them together, and unscrew them to disconnect.

SMB connectors are also slightly smaller.

SMA connectors are also far more common.

Personally, I would be much more inclined to go with SMA connectors, just because they're so much more easily available.
However, since this is going outside, I would more strongly recommend SMA, as it is much more mechanically reliable.

However, it's crucial to note that the Bulgin connector you link isn't really SMB. It's a SMB-style connector with a bunch more stuff on it. It's also exclusively available from Bulgin. However, realistically, any high-frequency IP67 connector is going to be non-standard (well, aside from N connectors), as there aren't really any standards for sealed high-frequency connectors, so the fact that it's Bulgin-Exclusive isn't really a big deal, as anything else will be similarly single-sourced.

On the whole, If you really need IP67, I can highly recommend the Bulgin Buccaneer connectors. I use several varieties of them in a device I designed, and they are very nicely made. Just be aware that you will need to make your own cables (which involves crimping/terminating coax), if the few varieties Bulgin offers do not suffice (and the longest cable they do make is 5M).

Is there any reason you can't use a N connector on your equipment? The only real downside to N connectors is they're large.

• I thought a SMB when connected to a cable had a little more insertion loss than an SMA that was connected to a cable and properly torqued? I wish I still had access to my TDR or network analyzer to prove it though. – Some Hardware Guy Oct 4 '12 at 12:29

SMB are snap-type, while SMA are screw-type connectors. That makes that SMB is somewhat smaller than SMA, but the main difference will be in connecting/disconnecting: a screw-type connector makes for a more sturdy mechanical connection, it won't disconnect if there's some strain on the cable. A snap-type like SMB on the other hand is more convenient if you have to connect or disconnect more often, and can be sure there won't be any pull on the cable.

Electrically they should be equivalent.