Quest for cheap(er) SMA connectors - are the ones on Ebay any good? - Page 1
Forum section: electronics / general

author: chicken
author_rank: Frequent Contributor
timestamp: August 14, 2014, 06:16:41 pm
content: For some reason, SMA edge connectors are pretty pricey at regular distributors ($3+ in singles, 75% more expensive than big clunky BNC blukhead jacks).As always there's plenty of supply from China on Ebay for 50 cents and less. But are these any good for modest RF applications (<<1GHz)? Did anyone verify impedance, dimensions and other parameters? Any comments on physical quality?

author: KJDS
author_rank: Super Contributor
timestamp: August 14, 2014, 06:41:33 pm
content: I've seen some that have brass instead of beryllium copper as the center contact. Fine the first time you use them, but it isn't hard and springy enough to be used more than once. Haven't bought any in ages so I can't recommend any. Might be worth buying a few from different sources to make sure they are ok.I'd be surprised if any of them were bad for impedance.

author: Precipice
author_rank: Frequent Contributor
timestamp: August 14, 2014, 06:59:08 pm
content: I've got through thousands of SMA sockets of various types from ChinaRF on ebay. They've given me less grief than legit Lemo sockets!My customer only ever uses them once, maybe twice, but I've put hundreds of matings on them in the lab.Some of them, especially long reach right angle parts - I suspect the gold isn't gold, it's an odd colour and seems to come off.(Last time I looked, RS had price breaks on some genuine TE SMA sockets that made them competetive enough that I bought a few hundred. They all turned up in individual bags, even though I bought 'production packaging', and stripping them out of the bags was tedious. Sigh, can't win.)This is all at low frequencies, though. No idea about their high RF performance.

author: Bud
author_rank: Super Contributor
timestamp: August 15, 2014, 06:22:51 am
content: OK for prototyping, shame for production. Typical physical quality is poor, it is rarely that I am lucky to get brass, almost everything is some unknown thin light metal coated by another unknown metal, tabs are bent and trying to fix may break the tabs, center contacts with insulator (probably not Teflon either) not tight in the barrel and I saw some falling off of the metal shell and center pins been pushed in or pulled out during mating. The soldering part of the center contact comes in a variety of thicknesses, forget about definitive impedance characteristics. Spacing between PCB tabs not controlled and may be too wide or too tight for a PCB to get there. Still, for casual prototyping cannot beat it and used up to 3GHz on FR4. For production runs I would not use them. Having said that, I did get quality brass ones from China several times, could be surplus of real products though and not from that particular vendor.

author: chicken
author_rank: Frequent Contributor
timestamp: August 15, 2014, 06:04:16 pm
content: Thank you all, great input.

author: David Hess
author_rank: Super Contributor
timestamp: August 15, 2014, 08:40:51 pm
content: I am about 50/50 on cheap Chinese connectors but even the ones that work have been marginal as far as fit and dimensions. They are adequate for prototyping but I would qualify them per order or lot for production and plan on a lot of returns.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 16, 2014, 04:38:57 am
content: Quote from: David Hess on August 15, 2014, 08:40:51 pmThat could be the biggest problem - consistency. One order might be fine, the next might be crap. If you're trying to use these connectors for anything other than personal use it would be a nightmare.Ed