Talk:SMA connector

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SMA should be an article in itself. Scott 19:05:23, 2005-09-07 (UTC)

Why? Light current 19:06, 7 September 2005 (UTC)

Why is there a reference to particle accelerators in the first paragraph? SMA connectors are used in mass numbers for other much more mundane things too. 14:52, 25 May 2006 (UTC). I took it away sincer it was only confusing. saved here for future recalls: "The SMA connector is frequently used in mass numbers in particle accelerators. The connector is used in conjunction with Heliax cable as a connector for X and Y in Particle beam diagnostics, after Quadrupole magnets. The AC feedback signal, X and Y are fed through four SMA connectors from the beam position monitor to the beam monitor instrumentation."

Reverse Polarity[edit]

The description of reverse-polarity SMA connectors contradicts the images. The top image of a standard SMA connector shows a male connector (with a pin rather than a socket in the centre). The bottom photograph, according to its caption, shows a male RP-SMA connector, which has a pin and a different housing from the ordinary male SMA connector. But the text states that male SMA and RP-SMA connectors differ by their centre contact, not their housing, and that a male RP-SMA connector has a receptacle (socket) in the centre. Does anyone know which is right, the caption or the text? Please correct the article if you do. 07:37, 1 June 2006 (UTC)

  • The article is correct, but it is missing one important piece of information. It is not enough to specify, for example, "SMA Female connector". Male/Female refers to the centre Pin/Socket. i.e. Pin for Male, Socket for Female. But you also have to specify whether you are talking about a Plug or a Jack. A Plug has the thread on the inner surface, while a Jack has the thread on the outer surface.
  • The 'reverse polarity' term is a misnomer and leads to a lot of confusion. We cannot change the term as it is already widespread, but the misnomer nature needs to be pointed out as it confuses RF engineers who are not from the WiFi trade as well as people with electronic background. A more correct term would have been 'reverse gender'.
  • It should perhaps also be pointed out that Male/Female always refers to the pin in every other connector standard in the world, but with the article's 'reverse polarity SMA' explanation, Male refers to the plug, not to the pin.
  • "Standard-Polarity" SMA specifies that Plugs are Male and Jacks are Female.
  • "Reverse-Polarity" SMA specifies the opposite: Plugs are Female and Jacks are Male.
So the top image shows a (standard polarity) SMA Plug (with centre pin), and it is captioned correctly. The lower image shows a Reverse-Polarity SMA Jack (with centre pin). It is captioned correctly, except that the word Jack is omitted.
BenKinsella 17:04, 29 March 2007 (UTC)

Figure 2 is *not* captioned correctly. By standard convention it is an RP-SMA Female connector. An RP-SMA Male connector has a hole in the center, and threads on the inside. The "male" and "female" part of SMA connectors are in fact consistent. It's represented by the inner ground housing. Male housing always plugs inside female housing, whether normal or reverse polarity. (talk) 03:37, 29 August 2009 (UTC)

I disagree. Yes, the text and picture are in contradiction, however, gender of a connector is _always_ determined by its center pin. The outer shell determines if it's a plug or socket. For instance: is a female connector because the center pin is female.

10 Jan 2011 sank

After further review, I could be wrong. I guess people do make their own conventions.

10 Jan 2010 sank

Sank had it right the first time but both links have errors in them. The gender of a connector is, indeed, named by the configuration of the center conductors connecting parts. Look at the naming used on all other coaxial connectors and you will see that the thread gender is exactly opposite the connectors name if it is the normal or common configuration. The use of the term "reversed polarity" is indeed unfortunate. Since reverse threaded already has a common meaning, to mean left hand rotation of the moving part in order to tighten the joint in the description of threaded connections, it would just cause confusion to apply it to coaxial connector threads. I don't see plug and jack as completely curative although it is certainly clearer than reverse polarity.

2Ø11/12/Ø8 Tom H — Preceding unsigned comment added by Hornetd (talkcontribs) 01:55, 9 December 2011 (UTC)


Why is there a reference to the "Snap-On" tool company on this page? The tool company has no relationship to an RF connector that can be pushed on and pulled off without turning a nut.

Agreed. I removed the link Amram99 24 Oct 2006 (UTC)

Could it be that, as I have noted below, a torque spanner should be used to tighten the SMA connector especially when used at microwave frequencies? --jmb 09:30, 6 March 2007 (UTC)

Thread Size[edit]

Could someone add the thread size for a female SMA connector? I'm trying to find a nut to hold one in place on an aircraft panel.

SMA mounting nut threads: .250-36 threaded coupling SSC four (talk) 20:14, 12 September 2008 (UTC)

Why not add some dimensional information? Would a drawing or sketch based on the governing specification be allowable? Mollynet (talk) 18:19, 14 October 2009 (UTC)


It offers excellent electrical performance from DC to 18 GHz.

Can this be expanded to say that there are SMA connectors for use above 18 GHz. Also when used at microwave frequencies a torque spanner should be used to tighten the connector. --jmb 09:30, 6 March 2007 (UTC)

Those connectors are not standard SMA. —Preceding unsigned comment added by (talk) 17:24, 1 April 2008 (UTC)

Most popular?[edit]

"SMA and precision SMA-like connectors are by far the most popular coaxial connector, though by modern standards, their performance and durability are somewhat limited."

Shouldn't that read "the most popular sub-miniature coaxial connector"? --jmb 09:15, 17 June 2007 (UTC)

SMA discussion[edit]

I found you are all right, maybe you are all great engineers.i'll study more from you —Preceding unsigned comment added by Cmpter (talkcontribs) 02:31, 4 June 2009 (UTC)

The SMA 'standard' is a complete disaster. There are connector manufacturers, component manufacturers and cable manufacturers that use their own conventions. So, if you want a buy a cable to connect an XBEE module to an antenna (all of them SMA parts), you have a very low chance of getting it right.

The best that can be done is to have 4 photos of the 4 variations, with a text description of the 'SMA' names and aliases. This would be a good starting point. However, I would not expect manufacturers to conform to this. What about an ISO standard, or is it too late? Orrcam (talk) 15:55, 27 December 2010 (UTC)Tim Orr

There is no problem as you describe it. An SMA connector is *NOT* an RP-SMA connector. You can't expect to mate connectors of different types. You wouldn't expect, for instance to connect a BNC connector to an SMB connector, so you should not expect to connect an SMA connector to an RP-SMA connector. Knowing the difference between them is merely an educational issue. 10 Jan 2020 sank

—Preceding unsigned comment added by (talk) 17:14, 10 January 2011 (UTC)

Technical Specs/Dimensions[edit]

I arrived at this page looking for the standard dimensions of an SMA connector for my research. I saw it thru the References section but it seems rather incomplete. Should it be better if we put the dimensional specs of the SMA standard here? Along with the SMB and SMC entry. So we can quantitatively see the difference. Thanks. (talk) 15:05, 14 January 2011 (UTC)

Article is confusing[edit]

This article is very confusing. It did not help me learn which connector type is which. SMA F/M and RP-SMA F/M should be clearly described with appropriate pictures. Please, if someone knows this matter and have some time to correctly explain things about 'SMA' connectors.

Somebody is wrong on the internets!!! ;)[edit]

I had to edit this article, because it was contradicting within itself, and showed EXACTLY the opposite of what it should! Pictures talk louder that words: --Valent (talk) 06:59, 19 September 2011 (UTC)

Suggest revert to Male RPSMA caption, June 30th version.[edit]

I'd like to suggest reverting this article to Mr PIM's edits at 20:38, 30 June 2011. SMA connector terminology is very tricky and I have referred back to this page like 60 times over the last year to make sure I ordered and specified the right genders, including using the terms plug and socket. Unfortunately, now those terms were removed from the text in the RPSMA section. Dif'ing Valent's contributions at Sept 19th 2011, most of them removed useful detail or added the 'pin hole' terminology which I don't like, or added advertising links to Linx's website. Good connectors and fine to link to their site in the talk page, but the link on the main page just seems like promotion. The one text addition I'd suggest retaining is "Today, however, both type of connectors are readily available." because RP-SMA is no longer 'unique'. Let me know what others think, to form consensus. Personally, I think Male RPSMA has a center pin and outer threads and would be called a jack/socket. Here are pictures at Mouser.

Otherwise, I'd also suggest someone add a more thorough comparison between 3.5mm and SMA because for a while I thought they were the same, but an RF friend pointed out there are slight differences, I think in the center pin length, that mean an SMA male plugged into a 3.5mm female will cause damage. The article currently notes that damage to 3.5mm female pins is possible with 'low grade' SMA connectors, but I'm wondering what dimensional tolerance is required to avoid this. Spazvt (talk) 08:18, 30 September 2011 (UTC)

Figure 2 caption[edit]

Could someone who understands the terminology please fix the figure 2 caption, which described a connector body with outside threads as female in one sentence and a connector body with inside threads as female in the next sentence. Both cannot be right.

"Figure 2.Female RP-SMA (RP-SMA-F or RSMA-F) socket connector: Inner pin contact with a female connector body (outside threads). A male RP-SMA connector is the opposite in both respects: It has a female inner pin hole contact with a female connector body (inside threads)."

And can someone explain the rationale for the use of male and female terms with RP connectors? Were they named by people unfamiliar with human anatomy? Does the "reverse polarity" really mean "reverse terminology", i.e. we are going to name these things opposite to what the words mean? Is there some purpose to this which makes it seem less incredibly stupid than it would be to produce a pair of "reverse feet" shoes where we refer to the left shoe as the right and vice versa?--Ericjs (talk) 18:12, 25 October 2011 (UTC)

I agree completely with Ericjs: pretty much all other connectors are named for the electrical contacts (BNC, TNC, SMA, XLR, D-sub etc. etc.) (see Gender_of_connectors_and_fasteners). With nuts and bolts, the bolt (thread on the outside) goes into the nut (thread on the inside) and the bolt is regarded as male (not surprisingly) and the nut female. What is really surprising is that the RP-SMA connector pictured here has male electrical contacts (pin) AND male threads (outside) so there is NO confusion as there might be with a TNC or SMA, and yet is labelled female. That can't be right??! Does someone not know the difference between the anatomy of male and female? If it has indeed become convention to call that connector female then it is a very weird convention and someone should explain it to us.


I searched Wikimedia Commons for SMA related photos and dropped them here but I didn't describe them. I'm not sure if all of these should be in the article, but I posted them here for people to see...just in case they want to use it in the article. Since the article isn't long enough to sprinkle photos throughout it, maybe we should add a gallery...just a thought.

Concerning the RP style connectors, this article should have RP style photos to show examples and give the common name that is found on the internet for them...the last thing that wikipedia needs to do is cause more confusion. • SbmeirowTalk • 12:28, 9 December 2011 (UTC)

Optical fiber SMA connectors[edit]

This article doesn't mention that the SMA designation is also used for a family of optical fiber connectors, which use the same thread size but have different centre pin dimensions. What's the best way to handle this - an extra sentence in the first paragraph, before the contents block, and/or an entry in the 'See also' list? (talk) 07:46, 4 October 2012 (UTC)

A new paragraph in the Variations section would be a good start. Do you have a reference? -—Kvng 19:57, 8 October 2012 (UTC)

SMA no good for "metrology"?[edit]

I added a "citation needed" tag to the statement regarding using SMA for "metrology". I think it's a strong statement of recommendation for how NOT to use SMA, even though from personal experience we use them for all sorts of measurement in our RF lab. It's also not terribly clear what is meant by "metrology" since almost any signal passing though a cable will be "measured" at some point. I hope this helps, and I submit this comment with respect. (talk) 19:27, 25 November 2012 (UTC)

General points, specification - I don't have time to cite all the reference, but here are some.[edit]

Contary to what the article said, they do not offer "excellent" electrical performance to 17 GHz. They are designed for use to 18 GHz, but I think the word "excellent" is mis-placed, as there are much better connectors - e.g. 3.5 mm, which by nature of its air dielectric will have lower losses than SMA. The female pin will expand in diameter when a male is inserted, causing a decrease in the impedance, unlike in the 3.5 mm precision slotless connectors, where the female is of a fixed diameter, and small fingers inside move to create electrical contact. I've added the word "semi-precision", as that is generally what they are known as. Here's two manufacturers who call SMAs semi-precision.

There's a graph in this book:

on page 36, which show insertion loss of SMA and 3.5 mm connectors. At about 12 GHz, the 3.5 mm is clearly superior. It actually in one of the sections you can see online at for free at Amazon, and probably elsewhere. Given the author of that book, Joel Dunsmore is Agilents top VNA expert, I think it is about as authoritative as any source.

The article also stated the life of 3.5 mm connectors would be reduced if mating with SMA and provided a web link to justify that. However, at no point does the word "reduced" appear in that link. The article warns of the risks of damaging 3.5 mm connectors if SMAs are out of spec, but as far as I know, there is nothing to indicate that SMAs within specification will damage a 3.5 mm connector or reduce its life. The problem arises because SMA are often out of spec when new, and so can damage 3.5 mm connectors. Drkirkby (talk) 12:06, 27 March 2013 (UTC)

There's a copy of the MIL standard for SMA connectors at:

but given the cost of the connector, one would be mistaken if thinking all connectors sold meet this specification. I expect there is more than one "Standard" too. What the old saying - "Standards are really nice and there are lots I can choose". Drkirkby (talk) 12:06, 27 March 2013 (UTC)

Removed comments from article[edit]

I removed these comments from the article, because non-encyclopedic. • SbmeirowTalk • 01:23, 27 August 2013 (UTC)

Connector design section

Note: The previous statement may not be true for RP-SMA. It contradicts the RP-SMA section below. I believe a female RP-SMA has external threads and a "male" center pin. References should be added to the alternate terms "plug" and "jack" for completeness.

Reverse polarity SMA section

RB: This is very confusing to many people, as they (incorrectly) assume that a connector labeled "male" must have a pin. Despite this confusion, the overwhelming industry convention for RP-SMA is clearly different as shown by the previous references.

Should reverse polarity be in a separate article?[edit]

I can't help feeling that it might be better if the RP version was in another article. Although the RP version is called a reversed SMA, it is totally incompatible by design. I was going to quote a few of the mechanical specifications on the SMA, but it would be confusing to do it in an article which something reversed is also given. The specifications are completely different. I've seen no evidence to suggest reversed SMA are rated to use at 18 GHz as the article says of SMA. Drkirkby (talk) 13:18, 13 October 2013 (UTC)

Yes, with such different characteristics, the reverse polarity connector should have its own article. Binksternet (talk) 13:56, 13 October 2013 (UTC)