What's the Difference Between SMA and TNC Connector

Discussion in 'Amateur Radio News' started by BH6PJL, Jul 4, 2019.

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  1. BH6PJL

    BH6PJL XML Subscriber QRZ Page

    Two most common antenna interface: SMA and TNC.
    The external wireless antenna looks like a similar look, but if you look closely, you will find that they have very different antenna interfaces. If the newly purchased external antenna does not match the radio interface, you will not be able to use it properly. Below we will introduce the two most common antenna interfaces, one called SMA and the other called TNC.

    SMA antenna interface
    The full name of the SMA antenna interface is the SMA reverse polarity male (SMA RP M). It can be divided into SMA and RP-SMA according to the difference in polarity. The difference between the two is that SMA means "outer helix + hole" and "inner helix + needle" design; while RP-SMA means " outer spiral + needle" and "inner spiral + hole" design.
    TNC antenna interface
    The full name of the TNC antenna interface is the TNC reverse polarity male (TNC RP M). It is thicker than the SMA male, and there is a metal shield between the outer and inner contact points of the antenna connector.
    Remedial measure:
    If we forgot to look at the interface type of the antenna before, what should we do if we bought the wrong one? Don't worry, we can buy an interface adapter that converts SMA to TNC or TNC to SMA.
    Note: Although there are remedies, we strongly recommend that you check the antenna interface type in advance, because using the interface adapter may have an impact on radio performance.
  2. K7MYR

    K7MYR Ham Member QRZ Page

    Great comparison!

    The TNC connector is dimensionally identical (internally) to the BNC connector (except one is threaded and one is "Bayonet" type)

    Both were named after the designers, and named Bayonet Neill Concelman, Threaded Neill Concelman

    They were patented by electrical engineers Paul Neill, Carl Concelman.

    Wikipedia actually has great pages on them complete with dimensions etc. (Neill also designed the N-connector)


    BNC and TNC connectors are not even dimensionally close to the SMA, at almost twice the diameter of the SMA.

    They (SMA connectors) do of course have real Amateur Radio uses I suppose, since manufacturers of some SDR equipment place them on some of the equipment they sell.

    This forces the user to either buy a rather expensive adapter or a cable. It would be nice if they put the more common (for the average Ham) BNC connector on this equipment since BNC connectors and adapters are very widely available new and surplus for little cost.


    WA7PRC, W3XOX and K4VLF like this.
  3. WY7BG

    WY7BG Ham Member QRZ Page

    The abbreviation "RP" really means "Reverse Pin," not "Reverse Polarity." (The connectors do not have a designated polarity, and in fact most often carry AC signals.) Which makes it easier to remember which ones are "reversed;" the connector with the outer shell normally has a pin. The TNC is an improvement on the BNC and has less loss at upper microwave frequencies.
    KJ3LR, WA7PRC, KA9UCE and 1 other person like this.
  4. KF5FEI

    KF5FEI Ham Member QRZ Page

    Umm... Modern HTs have SMA connectors as well. And some WiFi stuff.
  5. WY7BG

    WY7BG Ham Member QRZ Page

    The RP connectors were created when the FCC decided it would attempt to enforce Part 15 EIRP limits by making it difficult for consumers to attach a higher gain antenna to a device. For awhile there, it became the "Ministry of Funny Connectors," trying to make each vendor come up with something unique and incompatible. After awhile, it realized that it was putting an unreasonable burden on manufacturers and stopped doing this, leaving us with several "standard nonstandard" connectors. These include the various RP versions of the TNC, BNC, SMA connector, and N connector.
    WA7PRC likes this.
  6. KD0CAC

    KD0CAC Ham Member QRZ Page

    KX4O likes this.
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    I never seen a SMA that even came close to a TNC.

    A TNC is closer to a BNC.

    The sex got screwed up along the way.
    KD4MOJ and K8AI like this.
  8. WY7BG

    WY7BG Ham Member QRZ Page

    Personally, I wish that there were a bayonet connector like the BNC which offered the bandwidth improvements of the TNC and the water resistance of the N connector. Threads, a machine meant to provide mechanical advantage (which you hopefully do not need to seat a small connector!), are a pain in the posterior; they come loose and or stick at inappropriate times. Bayonets provide a positive connection that requires movement in two orthogonal directions - but not much force - to undo.
    NE1LL likes this.
  9. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    for being so common, I never heard of a TNC antenna connector before this thread.
  10. K7JEM

    K7JEM Ham Member QRZ Page

    TNC connectors were very common in old style mobile phones from the 80s and 90s. They are also used on some mobile lmr equipment, and some handheld radios. They are an excellent connector, and really should be first choice for most mobile radios. Better RF wise than PL259 or BNC, smaller form factor than type N. More robust than SMA.

    TNC doesn't get the love it deserves.
    WA7PRC, NE1LL, W0AMT and 8 others like this.

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