Pilot's helmet?

Discussion in 'Microphones, Speakers & Audio Processing' started by KD5RKO, Sep 8, 2019.

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  1. KD5RKO

    KD5RKO Ham Member QRZ Page

    Well I've got as far as testing and mapping out the wiring to the plug. So It's a four conductor, Tip Ring Ring Sleeve plug. The earphone pieces are wired in parallel, which is great as the 19 ohm earpieces in parallel come to 10.5 measured at the connector. So the Tip and the second ring away from the tip are connected to the microphone element. The first ring from the tip goes to the white earphone wire, while the sleeve goes to the black earphone wire. Each earphone "cup" has a black wire and a white wire. The earphone pieces themselves are loose and there is no material around them. Should I just cut a piece of foam to fit and maybe a dab of hot glue on the bottom of the element to secure it? Wiring.jpg 20190914_071355.jpg 20190914_071412.jpg
  2. KD5RKO

    KD5RKO Ham Member QRZ Page

    I'm planning at the moment on keeping it original. There are connectors at the end of the mic element so swapping in a standard piece would be easy. Just need to find a suitable circuit and test it out. Definitely in no rush to complete this. This on my just for fun and beacause I can list.
  3. W5LZ

    W5LZ Ham Member QRZ Page

    This is an opinion!
    If those speakers in the ear-cups are just floating around in there, someone screwed up.
    I think I'd suspend them 'firmly' in some way. I think a piece of foam glued to the back of the speaker and then to the 'cup', would be a very good idea. I think maybe a 'flexible' kind of glue would be best. It would dampen the amount of noise any physical contact with that ear-cup would make. Got a favorite color? Paint them!
  4. KD5RKO

    KD5RKO Ham Member QRZ Page

    Yeah I think someone either ripped out the foam to get at the elements or it had just deteriorated beyond usefulness and was removed.
  5. W4OKW

    W4OKW Ham Member QRZ Page

    I have worn those helmets enough (16,000 hours of mil time) that I wouldn't like one for "ham" use! Hey Bill "Set Condition 5". We (the guys up front) used either Telex 750s or David Clarks (especially in the noisy Herks). I have used the noise cancelling Electrets though, but they do need "bias". 8 volts from an Icom does fine. Some of the older mikes used a magnetic cartridge. I built an adapter so I could just plug my C-130 configured David Clark into it for ham use and still use it in the Herk. As MNM said, there are tons of schematics for interfacing the mil sets to a ham radio. I was fortunate that our rigger shop had a box with scads of those funky (and $$$) connectors. I have used the D-C headset at Field Day and it helps to keep out the other operators shouting "3A Maryland DC"! Also the noise cancelling feature keeps the above mentioned noise from going out on your transmissions. Have fun in any event! 73 de W4OKW
    KA0HCP, KB0MNM and KD5RKO like this.
  6. W8AAZ

    W8AAZ Ham Member QRZ Page

    In my experience, the military headphones were 600 ohms impedance and the mics elements were 50 ohms, little dynamic elements. Earlier on they were apparently all carbon like commercial aircraft. Commercial use 600 ohms headsets too, but the mics are either noise cancelling genuine carbon mics or "carbon equivalant" electret with an amplifier to take the carbon mic bias voltage from the plane and boost the output to carbon mic levels, rather high for most modern ham rigs.
    KD5RKO likes this.
  7. KB0MNM

    KB0MNM Ham Member QRZ Page

    As to the foam, almost all of it will eventually degrade- but any contact with petroleum-based chemicals ( aviation fuel or gasoline fumes, many contact cleaners, and paint thinners , etc. ) will cause foams to fall apart quicker. In replacement, you can see an upholstery shop ( they use foam in fixing up old chairs and sofas ) and they may ask if you want to buy closed-cell or open-cell foam, and how dense. As to new vinyl to hold the foam, an inexpensive set of headphones would be a cheaper donor than most special orders.
    Regarding that helmet microphone, if it is measured with an ohm-meter which uses a low battery voltage ( say under 4 volts ), there should be little chance of damage. Try connecting it to a little IC 386 based amplifier to see if it also needs bias. Some were carbon ( very early ), some magnetic ( dynamic ), but some later ones were electret. If you must replace the element, consider an IP-Rated ( as in for moisture resistance ) cartridge and save the old one with the connector. Thanks.
    KD5RKO likes this.
  8. WA8UEG

    WA8UEG XML Subscriber QRZ Page

    I made a box to convert my David Clark headphone I use in my 172 but it was short lived. while the head cruncher's definitely kept the noise to an absolute minimum I only made it 1/2 way through the 1st contest before putting them back in the flight bag.

    A nice set of Heil headphones are worth every penny for amateur use.
    KD5RKO likes this.
  9. KD5RKO

    KD5RKO Ham Member QRZ Page

    Do you remember anything about the circuit you made for it? I may end up replacing the earpiece elements with something better. I'm more doing this just because I can and it's there and it will be fun.
  10. WA8UEG

    WA8UEG XML Subscriber QRZ Page

    It was several years ago and I don't remember what exactly I did but I remember it was not a big deal. I did it from an article in CQ but it was also in QST, perhaps hint & kinks section but really can't remember.

    If your a ARRL member or CQ you can search their archives as the article was several years ago on building the converter box with the proper voltages and connections but it was complete with parts list.

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