Sex education for SMA connectors

[Paul Colby]

Okay, so I think I get the whole sex metaphor for coaxial connectors. I recently started buying SMA plumbing after I discovered RG-58 is essentially transparent in the FM band for my application. Now, typically a "male" designator refers to a connector having a little conducting protuberance while the corresponding "female" refers to a nice conducting receptacle for the aforementioned "male" bit. Okay, meanwhile in an alternate universe, "male" could refer to to the outer conductor equipped with exterior threads mating with the nice gold plated nut with interior threads. Okay, I buy 20 RP-FEMALE SMA bulkhead connectors only to discover that by the previous discussion the outer conductor is male and the inner conductor is also male. So, my question is two fold. A) In what convention system does this make sense. B) who on Earth would think making such a thing is a swell idea?

 

[berkeman]

Okay, so I think I get the whole sex metaphor for coaxial connectors. I recently started buying SMA plumbing after I discovered RG-58 is essentially transparent in the FM band for my application. Now, typically a "male" designator refers to a connector having a little conducting protuberance while the corresponding "female" refers to a nice conducting receptacle for the aforementioned "male" bit. Okay, meanwhile in an alternate universe, "male" could refer to to the outer conductor equipped with exterior threads mating with the nice gold plated nut with interior threads. Okay, I buy 20 RP-FEMALE SMA bulkhead connectors only to discover that by the previous discussion the outer conductor is male and the inner conductor is also male. So, my question is two fold. A) In what convention system does this make sense. B) who on Earth would think making such a thing is a swell idea?

LOL, funny thread title.

NP (normal polarity) has the male signal poke-out thing and inside threads on the outer nut/conductor/shield part.

RP (reverse polarity Female connectors have the female middle conductor, but have outside threads on the outer part (so that fits inside of the outer threads for the mating part.

One reason for the variations is that antennas have a couple variations of the connectors built-in, hence the need to have alternatives for mating with them.

EDIT / ADD -- https://en.wikipedia.org/wiki/SMA_connector

EDIT2 -- It looks like I may have mispoke about the center conductor determining the sex. From the wikipedia article:

Figure 2. Female RP-SMA connector: Female connector body (outside threads) with a male inner pin contact. A male RP-SMA connector is the opposite in both respects — male connector body (inside threads) with a female inner sleeve contact.

I always have to double-check the pictures when ordering RP SMA parts...

 

[Paul Colby]

One reason for the variations is that antennas have a couple variations of the connectors built-in, hence the need to have alternatives for mating with them.

Why introduce potential confusion? Of course the image you show wasn't available (the one missing view angle in fact) but until now the horror of such a possibly hadn't occurred to me.

 

[berkeman]

Why introduce potential confusion?

That's a valid question, with an interesting answer.

Many FCC-approved RF transceiver devices that have detachable antennas are approved only for the antenna the device was approved with during FCC testing. They don't want you to be able to easily connect a larger antenna with lots more gain via a standard SMA cable. So the output SMA connector on the device is RP, expecting an RP SMA antenna, not a standard polarity SMA coax cable. Of course, with SMA adapters, you can circumvent that issue, but that's one of the original reasons for the RP option. There could be others as well...

 

[Paul Colby]

I would argue the proper name for the part I bought should be RP-MALE.

 

[berkeman]

RP-MALE.

This?

http://www.nghobbies.com/wp-content/uploads/2015/09/rp-sma-male.jpg

 

[Paul Colby]

The above would clearly be "RP-FEMALE".

 

[berkeman]

The above would clearly be "RP-FEMALE".

Apparently not. See the name in the link. And Wikipedia seems to say the "sex" goes with the outer conductors thread sense...

 

[Paul Colby]

Apparently not. See the name in the link. And Wikipedia seems to say the "sex" goes with the outer conductors thread sense...

Thread sense makes no sense, IMO. Unless of course if they are left-handed as well. They screwed up and they rely on people like me to buy their products by accident.

 

[Paul Colby]

Okay, one of my RP-FEMALE bulkhead connectors paid the ultimate price. I pulled the mislabeled male bit out. A standard NP-MALE connector screws on just fine so the handedness of the threads is right-handed.

 

[the_emi_guy]

RP male has both female contact and female thread. It is still referred to as male because it is a normal SMA male that has had a sex change operation.
In other words "reversed male" = female

 

[OCR]

They screwed up...

.

 

[davenn]

RP male has both female contact and female thread.It is still referred to as male because it is a normal SMA male that has had a sex change operation.
In other words "reversed male" = female

that really doesn't make sense and doesn't go with common info available

did you not read Berkeman's post #6 ?

 

[the_emi_guy]

that really doesn't make sense and doesn't go with common info available

did you not read Berkeman's post #6 ?

What doesn't make sense?

That connectors that have all female parts would have the word "male" in their description, or my explanation of that odd situation?

Berkeman's post #6 is just a picture of an RP Male (with all of its female parts).

 

[Paul Colby]

It takes 2 bits of information to describe 4 possible configurations. Two of these configurations have been given stupid and misleading names. I will adjust to this situation though it may take some time to heal. Two of the configurations are in common usage and the other two are pointless from my perspective. While the "Let's make this inconvenient to plug a non-standard antenna in" explanation for the two pointless configurations may be industry standard, it is a lame excuse.

 

[the_emi_guy]

It takes 2 bits of information to describe 4 possible configurations. Two of these configurations have been given stupid and misleading names. I will adjust to this situation though it may take some time to heal. Two of the configurations are in common usage and the other two are pointless from my perspective. While the "Let's make this inconvenient to plug a non-standard antenna in" explanation for the two pointless configurations may be industry standard, it is a lame excuse.

Berkeman's "inconvenient to plug in" explanation is correct, and it was not initiated by engineers, but by lawyers at the FCC. Search for "unique connectors" in the attached fcc rules document.
As far as I know, no one uses these reversed connectors except to hack around FCC pre-approved antennas (or the folks making FCC approved equipment) so maybe it really doesn't matter what they are called.

 

[jim hardy]

'Tis a fine madness...

http://www.amphenol-aerospace.com/connectorbasics

http://www.amphenol-aerospace.com/pdf/faq/knowconnectors.pdf

 

[the_emi_guy]

'Tis a fine madness...

http://www.amphenol-aerospace.com/connectorbasics

http://www.amphenol-aerospace.com/pdf/faq/knowconnectors.pdf
View attachment 217364

And circling back to the post title, check out the note at the bottom of page 29 of the knowconnectors.pdf link.

 

[jim hardy]

And circling back to the post title, check out the note at the bottom of page 29 of the knowconnectors.pdf link.

But there's a wise guy in every design group.
Some wag just had to invent a "Hermaphroditic Connector" .

https://www.digikey.com/catalog/en/partgroup/hermaphroditic-connectors/24517#datasheets

 

[dlgoff]

And circling back to the post title, check out the note at the bottom of page 29 of the knowconnectors.pdf link.

 

[Tom.G]

Some wag just had to invent a "Hermaphroditic Connector" .

I've used some of that type, albeit decades ago. The sometimes un-appreciated utility is if you get the style that allows the contacts to be inserted in two positions (rotated 90°), you can key the connectors many different ways, specifically 2^{<No. of pins>}. Useful in large systems. (But you better document it well!)

 

[OCR]

Some wag just had to invent a "Hermaphroditic Connector" .

Lol, believe it or not, ambiguous gender, and genderless (hermaphroditic) connectors are the... "in or not in " thing now... .

 

[davenn]

Lol, believe it or not, ambiguous gender, and genderless (hermaphroditic) connectors are the... "in or not in " thing now... .

over the last 15 years, one I have used dozens of are the genderless Anderson Power Pole connectors
@berkeman may be familiar with them... much loved in the amateur radio fraternity

 

[davenn]

an oldie is the General Radio GR-874 hermaphrodite coaxial RF connector

and the RF APC-7
https://en.wikipedia.org/wiki/APC-7_connector