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Connector Center Pin Problem?

Discussion in 'General Technical Questions and Answers' started by ND5ND, Aug 26, 2010.

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  1. ND5ND

    ND5ND Ham Member QRZ Page

    Does any one know what kind of connector this center pin (see picture pin on left) goes to?

    It came with the bnc connector but it does not fit inside the insolator part.

    The pin on the right is the correct size that I got from a similar bnc connector.

    Also does anyone have/know a way I might be able to buy 3 properly fiting center pins (like the one on the right in the picture)?

    73, ND5ND

    Attached Files:

  2. VK2TIL

    VK2TIL Ham Member QRZ Page

    It might be a 75-ohm BNC; these have a larger centre pin. The two types are not usually marked as 50 or 75 and can be easily confused; if they are from a reputable maker like Amphenol, the part number on them can be searched to find the specs.

    It's claimed that a 75-ohm BNC will mate with a 50-ohm one;

    I think that's sometimes true and sometimes not; it depends on who makes the connectors. I don't take the risk; I always ensure that I'm buying 50-ohm ones.

    I think that I've occasionally seen packs of pins for sale, probably on ebay; just had a quick look there but saw nothing.

    I think that BNCs are a very risky proposition to buy these days; their use in ethernet has brought millions of very poor quality BNCs onto the market.

    I like BNCs and use them a lot but I take great care to buy good brands from reputable distributors.
  3. NN4RH

    NN4RH Subscriber QRZ Page

    I've seen those around the lab I work at. They're intended for high voltage (kilovolt), low current applications. I don't remember what they're 'officially' called. We just call them "high voltage bnc connectors'.
  4. W8JI

    W8JI Ham Member QRZ Page

    I'm not sure what the extra tapered pin is for. I've never run across that, but the connector manufacturer would know. It might even be an accident.

    The pin diameter and connector interface dimensions are all IDENTICAL in all BNC connnectors, either 50 or 75 ohms. The sole difference is in the insulation and sometimes dimensions away from the mating areas. The 75 ohm has a much bigger insulation airgap up in the body of the connector.

    Thus a 75 ohm BNC mates perfectly to a 50 ohm BNC.

    What people are confusing is a type N with a BNC. The type N has different pin dimensions for the 50 and 75 ohm types. If we mate a 75 ohm female with a 50 ohm male type-N, the male will split the female center pin contact because it is too large. If you fit a 75 ohm male to a 50 ohm female, the female is too sloppy and the male won't have good contact.

    The 50 ohm N is dimensionally almost identical with ALL BNC connectors in the contact area. As a matter of fact if we remove the locking mechanism of the male BNC it can be used as a quick connect push on to the N female, and a type-N 50 ohm male can be used as a push-on to a BNC female of either 50 or 75 ohms.

    There are also HV BNC style connectors called MHV and SHV connectors, and high voltage N connectors called HVN connectors. You do not have a MHV or SHV high voltage BNC-style. They do NOT interface to normal BNC's.
  5. ND5ND

    ND5ND Ham Member QRZ Page

    Thank you all for your reply's


    Thank you all for your posts/help. 73's to all. ND5ND
  6. ZL3GSL

    ZL3GSL Ham Member QRZ Page

    The red gland ring possibly indicates that it's a high voltage connector.

    I think that they are made to NOT make a connection to a BNC connector, for obvious reasons.
  7. VK2TIL

    VK2TIL Ham Member QRZ Page

    Still a puzzle; I've looked at the H + S specs for SHV and MHV connectors and the pin diameter for those is the same as the standard BNC (0.053"/1.32 mm).

    This is a good read about BNCs;

    There are some comments on "BNCs" that do not meet MIL-C39012 at the end of page 2 and onto page 3 and comments on older "75-ohm" BNCs at the end of page 5.

    The message is; buy Amphenol, H + S or other reputable makers' products and all will be well.

    Incidentally, ND5ND; is there any maker's name, type number or the like on this connector?
  8. KL7AJ

    KL7AJ Ham Member QRZ Page

    The pointier pin is a 75 ohm pin. It's slightly smaller in diameter on the business end.

  9. VK2TIL

    VK2TIL Ham Member QRZ Page

    No; I don't think it's smaller, I think it's the same, just not tapered.

    This is how I understand it;


    And BNCs are supposed to have the same pin diameter.

    It's the part that fits into the insulation that's larger.

    The H + S specs for 50-ohm BNCs specify a diameter of 81 - 87 thou/mils for this (non-mating) part of the pin; the pin on the right looks about that.

    Unfortunately, H + S don't give that level of detail for 75-ohm BNCs.

    The "mystery" pin looks to have a diameter, in that area, almost 3x the mating-section diameter; 3 x 53 thou = ca. 0.150" or 5/32".

    If all other factors remain the same, increasing the diameter of the inner conductor should lower Zo.

    Even if the OP could obtain standard pins, they wouldn't fit properly in the insulation.

    Best thing; bin them!
  10. WA7KKP

    WA7KKP Ham Member QRZ Page

    MHV connectors

    The MHV looks very similar to the standard BNC, but have an extended dielectric that sticks out beyond the end of the connector. They're good for ISTR 5kv.

    Gary WA7KKP
  11. W8JI

    W8JI Ham Member QRZ Page

    BNC 75 ohm and 50 ohm connectors have the same pins, business end or not.

    The difference in all of them, even the MHV, is in the dielectric.

    The exposed pin areas, both the female and males, are the same.

    73 Tom
  12. ND5ND

    ND5ND Ham Member QRZ Page

    Thanks for all the posts

    The beefier center pin is not meant of the connector at all, I had a Astronautics Lab Engineer look at it here where I am at. And the other pin the smaller one fits it, so who ever gave the guy I bought the connectors from, which I returned for a refund, was originally given the wrong center pins for the BNC's. The rubber ring is just for insulating. I kept the smaller pin and one of the outer housings, which fit the BNC ports on my stuff just fine.

    So it was a miss matched pin. Just thought I would ask you all.

    I appreciate all the responses this generated

  13. W0LPQ

    W0LPQ Ham Member QRZ Page

    The rubber ring is NOT for anything to do with insulation. It is for weatherproofing the connector inside.
  14. N8ODF

    N8ODF Premium Subscriber QRZ Page

    The mis-matched pin looks to be a center pin for an "N" type connector...73
  15. K8JD

    K8JD Ham Member QRZ Page

    I was trying to type that info myself. The larger end of the mystery pin may be for a type N for RG8 type cable.:eek:
  16. ND5ND

    ND5ND Ham Member QRZ Page


    I really did not expect this many post on this question, but thank you all for your input.:eek:

    I have already returned them.

    I talked with a lab tech that has been working in comms and space comm systems for years, he said they are bnc pins but the mystery pin is meant for a different brand and connector housing that accepts the OD of the mystery pin within its insulation.

    73s to all, I really don't plan on checking in on this again so do not feel bad if I don't get back with you on this.

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