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SO239 bulkheads in metal issue?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG5CWF, Jun 19, 2017.

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  1. KG5CWF

    KG5CWF Ham Member QRZ Page

    I have never done this before but I am doubting myself a little. I am finishing my SKB go box for field day and was about to drill holes in a 2U blank for the rack and put 2 SO239 bulkheads to make easy connection points for the coax. One is HF and the other is for VHF/UHF. Could there be an issue with RF or SWR with the threads contacting the metal or am I over thinking it?
     
  2. N1CZ

    N1CZ Ham Member QRZ Page

    Assuming that you are using metal "nuts" and the usual metal washers, the threads need not make contact.
     
  3. K9ZMD

    K9ZMD Subscriber QRZ Page

    No, there is no harm. It's all at ground potential, no different from the coax jack mounted to the metal of your transceiver chassis. Go ahead and drill holes for the bulkhead connectors.
     
    AF6LJ likes this.
  4. KB0MNM

    KB0MNM Ham Member QRZ Page

    I agree with the others. Your hardware for an SO-239 will need to be smaller than 6-32, use 4-40 if you go standard rather than metric ( or you may have some work ).
    I would also recommend: Inside-hole 'star washers' for the nut side, and some sort of corrosion protection. Chances are good that your panel will be coated steel, and the hardware could be coated with 'chrome', nickel ( same thing as chrome, basically ), or stainless-steel ( usually more expensive ). Put the connector on the outside unless you want the PL-259 shield not tightened as it could be. Use a longer 4-40 screw/bolt ( if needed ) to hold a lug to the SO-239 body if you are using a coax inside. If you are using the panel instead, consider an extra washer or two between the panel and the SO-239, then a bead of waterproofing around the 'square' and on top of the screws when done. Nutdrivers are easier later than finding the correct screw-driver slot cleaner. The hole size should be the 'backside' diameter of the barrel. Have fun & a great field-day.
     
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Just use high quality bulkhead connectors, especially for the VHF side.

    I've seen cheapie imports that were horrible.

    Amphenol and other American vendor materials are fine.
     
  6. KC8VWM

    KC8VWM Moderator Staff Member Volunteer Moderator QRZ Page

    Watch out for fake Amphenol connectors.

    Buy from reputable American based sources.
     
  7. KG5CWF

    KG5CWF Ham Member QRZ Page

    I may have miss spoken a bit. Let me clarify. I am using the all thread connectors through metal. Corrosion and water not an issue since this will be contained inside a skb or "gator case" and will only be exposed when i open the panels to operate. I have done this before through the exterior of a plastic ammo can for a qrp go box. And one example i have done using plexiglas, this is the first time using metal to have two right next to each other. I really appreciate the help so far. 1497925663349907029164.jpg
     
  8. KG5QBI

    KG5QBI Subscriber QRZ Page

    The barrel is still ground, just like the bolt pattern on a panel mount connector. The only way it could cause any issues is if you have common mode current, the metal may both radiate, and be a potential source for RF burns. Of course, the equipment it is pasing through to will have the same concerns if common mode currents exist.
     
  9. WA7PRC

    WA7PRC Ham Member QRZ Page

    The "UHF bulkhead adapter" is Amphenol pn 83-1F (aka UG-363/U, link). There have been MANY clones and variations of this part. When I created my feedline ground bus, I used silver-plated parts from DX Engineering (pn DXE-363-SST) at $7.45 ea:
    [​IMG]
    The nickel-plated version (pn DXE-363-SST-NI) saves the cheapskate a coupla bux.
     
    NH7RO likes this.
  10. G0GSR

    G0GSR Ham Member QRZ Page

    Do yourself a favour and switch to N connectors.
    The PL/SO239 series are an awful connector for many reasons.
    Frank, g0gsr
     

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