Electronics > RF, Microwave, Ham Radio

SMA vs SMA-RP

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uer166:
New to RF and I see regular SMA and "reverse gender" SMA-RP connectors which obviously aren't compatible, and there doesn't seem to be a good reason as to why. Is there any advantages of one vs. the other? I currently have random SMA, SMA-RP, N, BNC stuff and it would be nice to standardize on one kind, but equipment in the wild seems to have any and all combinations.

antenna:
SMA-RP are typically used for wifi applications.  Why?  I have no clue.  I can only assume it was to limit the use of external antennas by those who happen to have the standard SMA cables back when these SMA to SMA-RP adapters weren't so commonly available.  Perhaps I am wrong and it was a way to prevent someone from accidentally using a baofeng antenna on the router and frying the output...  Today, the RP connectors are exclusively used just to piss people off.

TheUnnamedNewbie:
After having ordered 50 RP-SMA's by accident at some point I went digging, and what I found back then was that this was an attempt to ensure that 'silly consumers' would use the wrong antennas or connect 'non-original' accessories to the antenna ports of their wifi routers.

But in the end the issue is the same as whenever people make custom screw heads or other non-standard components: The accessory markets takes about 3 days to figure it out and pivot to your 'custom' solution.

evb149:
Definitely use some standard connector, not something non-standard.

SMA is advantageous over BNC because SMA connectors are often designed to handle higher frequencies with better signal quality than BNCs were designed to handle.

Yes you can buy bad quality BNC or SMA connectors or cables or anything else and they will only be barely suitable for VHF or UHF frequencies and probably mechanically poor otherwise.

But you can get quite good SMAs / cables that are robust and high quality up to several GHz if you need that, and there are medium-grade SMAs that are much lower cost acceptable for lower frequencies like HF / VHF / UHF / 2.5G if that is what you need at a given place.

And SMA is more compact and uses more easily better selections of cables though it can be adapted to any coaxial cable of course.

The main disadvantage of SMA vs. BNC in my opinion for lab bench gear is just that it is harder to mate / unmate the SMA properly vs. the quick half-turn and pull that is OK for BNC.  So an oscilloscope probe or function generator test lead or something using SMA would be less convenient to attach / detach than SMA for mechanical reasons.   So that and cheap / common cables is why if you are only using HF/below frequencies maybe for some instruments BNC cables can be convenient.

ejeffrey:
Yes, RP-SMA is strictly a FCC compliance thing for consumer electronics that is approved for use in the ISM bands only as specified by the manufacturer.  You aren't supposed to attach an external amplifier or 3rd party antenna to a consumer access point.  The RP-SMA is just supposed to make that slightly more inconvenient, but of course since the companies who develop and test these things need to connect them to test equipment, adapters exist.  But it at least means that people are slightly less likely to directly plug an access point into some off the shelf 6W power amplifier.  In any case, you basically shouldn't use RP-SMA for anything.

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