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Thread: Microphones in Astro Saber/Astro Specras

  1. #1
    standardmissile No Longer Registered

    Default Microphones in Astro Saber/Astro Specras

    Anyone know the average frequency range on the Electret mics used in the Astro Saber portables, their speaker mics, and the Astro Spectra mobile mics? I need to replace a batch (20+) of them as a favor for a local SAR detachment of CAP.


    PS: I don't mind doing the labor of fixing them up, as it is good experience to keep my soldering skills up to par, as well as helping out the CAP brats since their budget cant afford new (or surplus) ones.


  2. #2
    Alpha's Avatar
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    AFAIK they are pretty much garden-variety condenser mic elements. Characteristically, they have very wide frequency response (like 20-20K) or so and rely on the audio pre-processing circuitry to cut down the bandwidth to something appropriate for comms like 300-3000 Hz or so.

  3. #3
    standardmissile No Longer Registered

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    Quote Originally Posted by Alpha View Post
    AFAIK they are pretty much garden-variety condenser mic elements. Characteristically, they have very wide frequency response (like 20-20K) or so and rely on the audio pre-processing circuitry to cut down the bandwidth to something appropriate for comms like 300-3000 Hz or so.
    So would it be of any use to use these?

    http://www.jameco.com/webapp/wcs/sto...001_1950948_-1

    http://www.jameco.com/webapp/wcs/sto...0001_320179_-1

    Vs a radio shack equivalent like this?

    http://dlnmh9ip6v2uc.cloudfront.net/...D462P2.54R.pdf


    I've also got some surplus H-250 handsets from work to redo for my Brother's airsoft store, so that's why I'm paying a little more attention to the details.

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    .... Interfacing a H-250 with a AS or XTL, that would be a interesting project.

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    Any of those would most likely work. They all have built-in pre-amps and take 3-9V for supply, generally. The biggest issue would be the physical dimensions more than anything.

  6. #6
    standardmissile No Longer Registered

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    Quote Originally Posted by slim View Post
    .... Interfacing a H-250 with a AS or XTL, that would be a interesting project.
    Been there done that. It needs to have an impedance matching circuit, or replace the mic element due to the low inpedence mic used on the H-250 and H-350 handsets. I used a cable from a cheap Chinese Saber speaker mic I had at home with a spare U-232 plug over from logistics to make the adapter, and augmented the audio circuit in the H-250 by adding a potentiometer to allow audio levels to be independently adjusted, as well as replaced the speaker with a 1" 4 ohm substitute with a 90Hz-25KHz freq range. It's a b*tchin little homebrew that works a hell of a lot better than either the standard H-250 or the knockoff speaker mics I have.


    The CAP brats were sooo jealous to see that little invention. Most of them in the nearby Cadet/Composite squadrons use VHF XTS-3Ks or Astro Saber 1&2s, and I have on more than one occasion been called by my superiors to out of my office to go help them out.
    Last edited by standardmissile; Mar 01, 2013 at 11:15 AM. Reason: Grammatical error

  7. #7
    Will No Longer Registered

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    Question, WHY do the mic elements need replacing? Are you having some sort of problem?

    There IS a known problem with Syntor- Spectra mics, scratchy transmit, and that is not an element problem but a dirty switch.

  8. #8
    standardmissile No Longer Registered

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    Quote Originally Posted by Will View Post
    Question, WHY do the mic elements need replacing? Are you having some sort of problem?

    There IS a known problem with Syntor- Spectra mics, scratchy transmit, and that is not an element problem but a dirty switch.
    Water damage plus years of heavy wear and tear. They were originally donated as "surplus" from the feds and then they got worn into the ground by 16-18 year old cadets learning the basics of SAR/operational radio protocol. I don't know the exact causes as to why they need it, I just know that they require new mic elements because they sound worse than my gear (which still needs to be tuned), and theirs has been recently calibrated by a shop down in SD who came to the same conclusion.

  9. #9
    Will No Longer Registered

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    A little soap and water go a long way to clean the housings. Simple Green, ect.

    Probably will need to replace the felt cover in the mic housing. The felt on the electret cartridge, if there is no sign of rust/water on the felt cover, no need to replace the element.

    The switch is another problem, clean it with Craig's ProGold G5, a contact cleaner and conditioning treatment.

    Test the mics on a known good radio. Move the cord around to check for noise.

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    I use 409 and a hog hair brush. (no static)
    Put them (covers) in the ultrasonic cleaner for 5-10 minutes.
    Rinse with distilled water, shake off.
    Dry in the convection oven at 140F/60C for 30 minutes.
    Does wonders for the radios appearance.
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