Robust and small RF connector needed - Page 1
Forum section: electronics / rf-microwave

author: ChristopherN
author_rank: Unknown
timestamp: April 09, 2023, 11:34:47 am
content: Hi,I'm working on an application in which I need RF connectors (up to 6GHz) that can be plugged many times. I was looking at SMA or FAKRA, but most manufacturers rate them for 50 or less mating cycles or don't give anything on that topic at all. Some go up to a 100 cycles, but that seems to be it.I tried searching for other connectors, but did not really find anything thats not super expensive (the Rosenberger Medical stuff) or big (BNC) rated for many cycles.My wishlist:-Small, easy to plug (no bigger than SMA or FAKRA), smaller is better since I'll have up to 10 connectors on each device-DC to 6GHz-1.000 insertion cycles, more is better-Less than 3€/$ per connectorIs there anything that meets the requirements out there?BRChristopher

author: 1design
author_rank: Regular Contributor
timestamp: April 09, 2023, 12:18:09 pm
content: Have you looked at SMB and SMC? They are both rated for 500+ connections and are smaller or comparable to the SMA you were looking at.

author: horo
author_rank: Regular Contributor
timestamp: April 09, 2023, 04:05:35 pm
content: Quote from: karpouzi9 on April 09, 2023, 03:29:01 pmQuote from: ChristopherN on April 09, 2023, 11:34:47 am

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2023, 04:37:43 pm
content: Quote from: 1design on April 09, 2023, 12:18:09 pmSMB would be a reasonable choice IMHO. SMC is horrible to work with as you really need to torque the connectors in order for them to not go loose by themselves. Still I wouldn't put SMB (or SMC) connectors close together because you'd still need access with your fingers.

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2023, 04:59:03 pm
content: Still, using BNC for 6GHz gets iffy. On oscilloscopes you see that over -ballpark- 3 to 4 GHz the BNC connectors are being replaced by RF connectors. The measurement uncertainty simply becomes too large when using BNCs.Another option would be MCX connectors. AFAIK these are commonly used on high frequency oscilloscopes.

author: jonpaul
author_rank: Super Contributor
timestamp: April 09, 2023, 06:29:07 pm
content: See Semtech for small wideband RD connectorsSee Belden app notes on wideband connectors and cables, especially the application notes and blog of Steve Lampenjon

author: fant
author_rank: Contributor
timestamp: April 09, 2023, 08:19:59 pm
content: TNC, it is little bigger than SMA, but is rated to 11 GHz.Mandi

author: ChristopherN
author_rank: Unknown
timestamp: April 10, 2023, 05:42:01 am
content: Thanks for all the great replies, I have a lot of stuff to read nowMCX and SMB seem to be good choices.Regarding SMA I found this:https://edadocs.software.keysight.com/kkbopen/what-are-the-expected-connector-mating-life-cycles-for-various-keysight-precision-microwave-connectors-589746670.htmlSeems like it's really something I would need to test with different connectors. Datasheets on the SMA connectors you can buy are not really helpful.

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: April 10, 2023, 04:15:02 pm
content: This might not work for you but one alternative is to use a "connector saver" scheme where you replace the saver after so many mating cycles. If the end user can't be relied upon to count the operations and keep a stock of savers then it won't work.I'd also worry about keeping the connectors clean after so many matings. Many connectors generate fine metal shavings in the mating process.

author: Marsupilami
author_rank: Frequent Contributor
timestamp: April 10, 2023, 04:44:09 pm
content: To me it feels like your reliability and cost targets are in slight conflict, but I was wrong before.Amphenol specs their SMAs to 500 min cycles.My issue with basically all of the miniature snap in connectors is that in order to have adequate retention, they are quite difficult to remove, thus prone to user abuse. You didn't say who would use this in what kind of setting.A hand-tight SMA could potentially still give you better performance at 6GHz than an MCX that has been pulled out by the cable hundreds of times. The spec applies only to the mating interface.Another point for SMA is you can easily use a connector saver without any extra mechanical work, and you can extend connector life practically indefinitely.I want to mention HD-BNC too, because I find it cool. The 50Ohm version goes up to 6GHz. Amphenol rates them 500 cycles min, and you get the quick, reliable connect functionality in a small package. It's more expensive though.Good luck!

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2023, 05:31:47 pm
content: IMHO tightening SMAs with your hand is a nuisance. I'm moving towards SMB myself because it is much easier to work with. The disconnecton force isn't that high. Note that plugin-SMA adapters also exist on which you don't have to tighten the connection which would give a user both options.

author: rf-messkopf
author_rank: Regular Contributor
timestamp: April 10, 2023, 10:01:23 pm
content: Also, if a SMA connector is rated for 500 mating cycles, this does not mean that it will fall apart after 600 cycles. It just means that the manufacturer does not guarantee that it will meet all of its specs after that many cycles. Unless you have tight requirements e.g. on SWR, you are likely to get much more useful mating cycles out of the connector.Quote from: ChristopherN on April 10, 2023, 05:42:01 amThese precision air dielectric connectors are much more expensive than the 3€/$ per connector from your wish list. Do you really need metrology grade connectors?

author: Njk
author_rank: Frequent Contributor
timestamp: April 25, 2023, 11:50:43 pm
content: Quote from: rf-messkopf on April 10, 2023, 10:01:23 pmI can propose another interpretation. This number of cycles was measured using a calibrated test setup. So there is no misalignments, no excessive force, no dust/abrasive particles, no moisture, no sharp temperature changes, etc., etc. Real life time is likely shorter. Otherwise they would advertise 5000 or whatever number of cycles to better differentiate from the competitors.Edit: not mentioning their definition for durability