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Max RF power for typical BNC connector?

Discussion in 'General Technical Questions and Answers' started by OH2WW, Jan 15, 2010.

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  1. OH2WW

    OH2WW Ham Member QRZ Page

    What is the maximum RF power that can be passed through a typical BNC connector?

    A web search didn't turn up any answer.
  2. PA5COR

    PA5COR Ham Member QRZ Page

  3. OH2WW

    OH2WW Ham Member QRZ Page

  4. PA5COR

    PA5COR Ham Member QRZ Page

    Absolutely no problem.

    But stick to a good brand and quality connector.
    A BNC is dimensionally almost exactly the same as a N connector so far as the areas that carry current and voltage, so it is good to a kilowatt or more safely.
    Not that i would ever do that to be honest, but 100 watt is no problem.
    The cable connected to it is the real problem.

    If you question this, look at the pin size of the BNC and compare it to a 50 ohm N connector. They are nearly the same.

    Look at the spacing between the pins and the "shield area" of the connector, and they are almost exactly the same.

    As a matter of fact, a type-N 50 ohm male will plug right into a BNC female and make a good connection although it won't latch. I use male "N" as quick connect to female BNC's, and male BNC's with the bayonet removed as a quick connect to N female!!! You just barely have to tweak the shield contact to make it work.
  5. M0DSZ

    M0DSZ Ham Member QRZ Page

    200W on HF is no problem, 100W on 2m is no problem either.
  6. WD0GOF

    WD0GOF Ham Member QRZ Page

    The mil spec for the BNC states an rms max voltage of 500 volts up to 1 GHZ. The math ( E squared / R ) says 5000 watts. Which I find hard to believe. I suppose if the source and load Zo is truly 50 ohms that could be true. I do know that Navy gear in the '60's used BNC connectors up to 500 watts.

    73, walt
  7. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I've run 300 watts through them on 2 meters and UHF - no problems.

    My dad had a set of surplus power supplies that used BNC's for DC power connectors. I suspect it was for the high voltage capability. I think the supplies put out 150 or 200 V at up to 1 A. The connectors were never an issue, and I'd say if it was good enough for the military, it's good enough for me, even if it is very strange.
  8. K7JEM

    K7JEM Ham Member QRZ Page

    Motorola uses them on their Micor base station power amps at VHF and UHF. Those amps were rated at 100+ watts continuous duty.

    I once wanted to test a Micor UHF PA, so i put it on a wattmeter and dummy load and attached a 1 watt exciter to it.

    Keyed it up for 24 hours straight, came back and PA was quite hot, but still putting out 100 watts.

    If the BNC connector can handle that sort of use at 450MHz, it should have no problem doing many times that in intermittant amateur service at HF.

  9. KA4DPO

    KA4DPO Ham Member QRZ Page

    A properly constructed BNC connector can withstand 500 watts at HF. This is for a matched condition of 50 ohms. Keep in mind that the BNC is typically used in UHF and SHF systems that run a couple of hundred watts. That is more electrically stressful than HF. But just to be on the safe side you should keep the RF power below 500 watts RMS.
  10. WA9SVD

    WA9SVD Ham Member QRZ Page

    150-200 Volts is "High Voltage?":confused:
  11. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    I have been involved with a few high voltage BNC's. There was some kind of instrument that req'd it plus there are non-50 ohm radio applications (Hi Z) where even at low power the voltage was in the multi KV range requiring the BNC's to be quite a bit different then the std type (longer surface paths along the insulation somehow). 73, Pete
  12. WA7CC

    WA7CC Ham Member QRZ Page

    It is common for connector maximum voltage to be spec'ed as peak voltage rather than RMS. I don't know how the Mil Spec reads and I'm not saying that it's not RMS. just be sure to read the specs carefully.

  13. WA7PRC

    WA7PRC Ham Member QRZ Page

    In a 50 ohm system, you'll be limited by the current you can pass thru the contacts since...

    E = SQRT (P • Z) = 273.8 VRMS (387 Vpeak) @ 50 ohms & 1500W

    and the current is...

    I = SQRT (P / Z) = 5.5 A @ 50 ohms & 1500W

    I expect the connector would get quite toasty at kilowatt levels, over any significant length of time.

    Rule of thumb: If the contacts melt, you exceeded the current cabability. If the insulation arcs over, you exceeded the voltage cabability. :rolleyes:

    Bryan WA7PRC
    Last edited: Jan 17, 2010
  14. WD0GOF

    WD0GOF Ham Member QRZ Page

    The mil spec is MIL-STD-202. Check out
    The charts on this site have all the specs. Look for "working voltage at sea level".

    73's Walt
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