Kenwood / Wouxun Headset Jack Spacing

Wouxun plug mounting plate - overview

Wouxun plug mounting plate – overview

Try as I might, I cannot uncover a definitive answer to this simple question: What’s the center-to-center spacing of the mic and earphone jacks on the side of Kenwood and Wouxun HTs?

The usual searches produce answers like 11 and 12 mm, both of which are obviously wrong, as can be determined eyeballometrically just by holding a scale against the plugs.

Based on measurements I made on a Wouxun headset, the yellow plug mounting plate put the plugs on 11.2 mm centers and they fit into the KG-UV3D radio; it’s been working fine ever since.

However, having just measured a speaker/mic and a headset, both from Kenwood, I come up with 11.5 mm. Frankly, I trust the Kenwood hardware a bit more: the plugs seem more rugged and the overall production values are higher.

The calculation is simple: measure the pin diameters, then subtract half their sum from the outside distance across the pins. Cross-check by adding half the sum to the inside distance between the pins, which should give the same answer. It helps if the pins are actually round.

The jacks in the Kenwood and Wouxun radios have enough compliance to accept either a Wouxun or a Kenwood headset plug without complaint. Maybe it doesn’t matter?

Despite that, I made another gluing fixture with 11.5 mm spacing:

Plug alignment plate - 11.5 mm spacing

Plug alignment plate – 11.5 mm spacing

Those are 0.1 inch grids; it’s a little bitty block of smoke-gray polycarbonate from the scrap heap. The plugs are nominally 3.5 mm (which is not 1/8 inch in this universe) and 2.5 mm, with clearance drills #28 and #39.

Then I tried poking those 11.2 mm spaced plugs, now firmly epoxied in place in the yellow plate, and guess what: they don’t fit, no how no way. That’s not surprising, because there’s no compliance on either side of the joint and the plugs aren’t on the right centers for the fixture. Makes for a good No-Go gauge, I suppose.

However, I think I’ll tweak the solid model spacing to 11.5 mm and run off another plug mounting plate for the next radio.

FWIW, our ICOM IC-Z1A HTs use a sensible 10.0 mm spacing and that old fixture worked fine.

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  1. #1 by Keith Neufeld on 20-August-2012 - 09:30

    It sounds as thought you were measuring the pin spacing of plug assemblies that were already made? I think I would have supplemented that with a measurement of two loose pins in the jacks — again outside distance across the pins minus each pin’s radius. You might know of an insightful mechanical reason that that wouldn’t have been helpful?

    • #2 by Ed on 20-August-2012 - 11:02

      a measurement of two loose pins in the jacks

      I ran into several problems while I sat there at the bench, poking things into the radio and wondering what to do. [grin]

      • The jacks apply an asymmetric force to the plugs, so the plugs don’t emerge perpendicular to the radio and don’t lie parallel to each other.
      • The jacks lie in a recess that makes it impossible to measure down where it really counts.
      • The jacks lie under a rubber gasket with snug-fitting holes, so I’d probably be measuring the gasket rather than the jacks.

      The first problem burned me badly on an earlier iteration of this project with an ICOM Z1A radio: I firmly wedged a pair of plugs into the radio and had to break up the epoxy blob to extract them. Now I make alignment plates and gluing fixtures and I don’t have that problem any more. [sigh]

      Anyhow, I figured I’d just space my plugs the way the Big Boys do, but it’s not clear they all do the same thing…

      • #3 by Keith Neufeld on 21-August-2012 - 17:22

        The jacks making the plugs not parallel — that totally makes sense.

        You use a lot of epoxy — you obviously have the knack for mixing it right, which somehow I’ve never managed to pick up. But rereading your older post makes me wonder about jamming the plugs into the jacks and enveloping them in a Sugru wad rather than epoxy. I think it’d have enough give to allow you to extract the plugs. The question is whether it’s too soft to provide the protection you need.

        • #4 by Ed on 21-August-2012 - 21:15

          You use a lot of epoxy

          It’s the right hammer for a surprising number of problems; if I never want to take it apart, there’s no reason to bother with fasteners! Of course, that same logic annoys me no end when it’s applied to consumer electronics…

          I save plastic lids from raisin canisters and suchlike specifically for mixing epoxy: broad, flat, shallow, easy to smoosh the resin and hardener into a uniform mass. The house came with a supply of thin wooden sticks that are perfect for mixing epoxy; I have no idea where to get more of them, though.

          enveloping them in a Sugru wad

          That should work fine!

          Mostly, you just need something to protect the wires and hold the plugs in place; there’s no real strength involved. Epoxy putty is fairly strong, even if it’s not in the same class as JB Weld, and has the key advantage of not dripping.

          Mixing putty is dead simple: just cut a length from the rod and knead it together. Alas, my putty stock is aging out: the outer layer has formed a brittle skin. Still works …

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