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SMA Male to N-Type Female Adaptor... Beware

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  • SMA Male to N-Type Female Adaptor... Beware

    Just bought two on Ebay the other day... 3.24 each

    Supposedly SMA Male to N-Type Female Adaptor

    $_57 (1).JPG

    Should have looked at the picture more closely.

    3 days trying to work out why my antenna had taken on the the characteristics of a piece of wet string.

    I suspect that someone in China has made a batch of them and the market will be flooded with them.
    """Learning is a treasure which accompanies us everywhere"""

  • #2
    You need the one to go on a dongle with the core pin?

    Theres also confusion with RP-SMA which reverses the thread feed onto one that would normally be a socket.

    I got suckered with a SMA to SO239. They gave me one with the wrong thread type on the 239 side, meaning it was more /| than /\ and would not screw in AT ALL
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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    • #3
      Suppose the RP stands for Reverse Pin.

      So a RP SMA Male is not actually a Male plug, and same for RP SMA Female.

      SMA-and-TNC-Connector1.jpg
      """Learning is a treasure which accompanies us everywhere"""

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      • #4
        The WiFi router people invented reverse pin SMA to discourage people from adding external antennas in place of the small whip antennas.

        It is not hard to insert a small piece of wire into a reverse SMA to un-reverse it. Componenet leads from resistors or capacitors work for me.

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        • #5
          The problem started with the American rules on transmitting, as wifi transmits then in order to meet the regulations the antenna has to either be fixed or if it is removable then it must have a non standard connector to stop people plugging other antennas in, this quickly became a farce as the RP-SMA connectors that they standardised on became widely available, however this means that the rest of us who use 'proper' SMA connectors have to watch out and avoid the RP ones.
          I believe a similar situation existed with RC kit in the US, you couldn't just change crystals like the rest of the world do, you had to replace a sealed transmitter module, I have one of these transmitters, however it is quite easy to open the module and change the crystal, as I am in the UK it is quite legal to do so.
          As far as I know this crazy situation only exists with SMA connectors (at least I am not aware of any other RF connectors where this happens)
          Ben.
          FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

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          • #6
            This is RP-SMA Male. It lacks the center pin of SMA Male. Instead it has a hole in center like a SMA Female. That is why it is called "Reverse Polarity" or RP.

            The purpose of RP was to prevent people from connecting external antenna to their hand-held walkie talkies. The center wire connection will be missing due to lack of center pin.

            Till the time you get a proper connector, you can temporarily overcome this problem by cutting a short length of core wire of coax and inserting it in the center hole of RP-SMA you have. This piece of wire will act as center pin. Please see picture below.

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            • #7
              Guys,

              I'm a tad confused. Is it that the whole RP-SMA connector is different from the standard SMA connector in that the thread is reversed and/or the centre pin is missing/omitted? I can understand in plumbing (my dad was a plumber/gas fitter/welder by profession) and there is a valid safety reason for using left hand threads and different sized fittings so as not to interconnect gas and water (when they used to use the older galvanised water pipes and gas pipes which were both threaded). That's why our BBQ gas bottles have left hand threads.

              Is there some kind of safety reason for doing this with SMA fittings or is it something else alone, as has been pointed out? For a start I can't see how they can call a connector without a centre pin a 'male' fitting in the first place. Extremely confusing and as has also been pointed out, very easy to get caught out. There seems to be two issues highlighted in the posts above, no centre pin AND reversed thread, unless of coarse I've misunderstood the posts.

              Regards,
              Gregg
              Last edited by fungus; 2016-05-07, 03:10.
              YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

              Comment


              • #8
                Originally posted by fungus View Post
                Guys,

                I'm a tad confused. Is it that the whole RP-SMA connector is different from the standard SMA connector in that the thread is reversed and/or the centre pin is missing? I can understand in plumbing (my dad was a plumber/gas fitter/welder by profession) and there is a valid safety reason for using left hand threads and different sized fittings so as not to interconnect gas and water.
                There is no problem with the thread. The problem is in the pin & hole. It is called reversed pin (RP) because the pin & hole are reversed. The RP-Male has a hole & the RP-Female has a pin.

                If you fit an RP-Male to standard Female, the thread will fit perfectly, but since there is no center pin in both pieces, center wire will be open circuited, and this open circuit is neither visible nor obvious, unless tested for continuity.
                Last edited by abcd567; 2016-05-07, 03:07.

                Comment


                • #9
                  Originally posted by abcd567 View Post
                  There is no problem with the thread. The problem is in the pin & hole. It is called reversed pin (RP) because the pin & hole are reversed. The RP-Male has a hole & the RP-Female has a pin.

                  If you fit an RP-Male to standard Female, the thread will fit perfectly, but since there is no center pin in both pieces, center wire will be open circuited, and this open circuit is neither visible nor obvious, unless tested for continuity.
                  Thank you very much for the clarification,

                  Gregg
                  YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

                  Comment


                  • #10
                    Sorry I was a bit alarmist in the opening post and to quick to blame the "usual suspects".

                    Just was not aware of "reversed polarity" SMA plugs (or any other RF connectors) but still think it is correct to alert those looking to buy.

                    And also warning dodgy stuff coming out of China.
                    """Learning is a treasure which accompanies us everywhere"""

                    Comment


                    • #11
                      Originally posted by G8VXY View Post
                      Sorry I was a bit alarmist in the opening post and to quick to blame the "usual suspects".

                      Just was not aware of "reversed polarity" SMA plugs (or any other RF connectors) but still think it is correct to alert those looking to buy.

                      And also warning dodgy stuff coming out of China.
                      I for one did't take it as alarmist and indeed, it's good to let others know of these findings in order to be of help to those experiencing the same or similar situations. Thanks for bringing it up.

                      Regards
                      Gregg
                      YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

                      Comment


                      • #12
                        I am posting the 3 photos below for the benefit of a vast majority who are not aware that SMA connectors come in two varieties (SMA & RP-SMA), and that these two varieties, although screw-able to each other, result in broken connection due to pin & hole reversal.

                        The dimensions & threads of SMA and RP-SMA are identical and perfectly match.
                        The difference is in center pin & hole only



                        IMAGE 1 of 3



                        IMAGE 2 of 3



                        IMAGE 3 of 3


                        .
                        Last edited by abcd567; 2016-05-07, 15:50.

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                        • #13
                          I find the eBay sellers less relyable in quality, then for example AliExpress. It seems that everyone can just dump their sh*t on there. I'm currently an A3 member at AliExpress , and I must say so far I've not had a negative experience with these kind of products from them.

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                          • #14
                            Originally posted by HNJAMeindersma View Post
                            I find the eBay sellers less relyable in quality, then for example AliExpress. It seems that everyone can just dump their sh*t on there. I'm currently an A3 member at AliExpress , and I must say so far I've not had a negative experience with these kind of products from them.
                            I have up to now made 3 purchases from Ali Express.

                            First one was Orange Pi PC ($15)+Power Supply ($5)+Case($2.5) - Excellent Product.
                            Second one was repeat of first one after a gap of 2 months.
                            Third one is a lot of 5 pieces of 1090 Mhz SAW filters TA1090 ($13), now in transit, expecting delivery soon.

                            My experience for first two purchases is good, but for 3rd one I can comment only after I receive the item.
                            Last edited by abcd567; 2016-05-29, 02:15.

                            Comment


                            • #15
                              Originally posted by abcd567 View Post
                              I have up to now made 3 purchases from Ali Express.

                              First one was Orange Pi PC ($15)+Power Supply ($5)+Case($2.5) - Excellent Product.
                              Second one was repeat of first one after a gap of 2 months.
                              Third one is a lot of 5 pieces of 1090 Mhz SAW filters TA1090 ($13), now in transit, expecting delivery soon.

                              My experience for first two purchases is good, but for 3rd one I can comment only after I receive the item.
                              I assume you have not had to deal with a complaint? I have a couple times now and I must say that the their dispute system works really well. Sellers on AliExpress are more eager to give you a (full) refund to make sure they don't get bad reviews. eBay had the same sort of rating system but somehow it works better at AliExpress.

                              He I'm looking at those filters you've ordered. How to use them? I was expecting a round piece with two SMA (or similair) on both sides. But it looks like to be a solder piece??

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