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Rig compatibility: D-104 w/500 ohm dymanic element

Discussion in 'QRP Corner' started by KA5NLY, Sep 25, 2020.

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  1. KA5NLY

    KA5NLY Ham Member QRZ Page

    I'm looking at using my D-104 mikes with my QRP rigs. Since the worn out high impedance crystal elements are shot, I'm gonna replace them with 500 ohm dynamic elements. Of course I then need to know what I may need to do to match them to my QRP Radios.

    The manuals for both of my Ten-Tec Argonauts (509 & 515) state they they need a high impedance microphone, but neither manual states how high the impedance should be, so I don't know what I need to do to match the D-104 to them.

    Then there is the Xiegu G1M...the so-call manual that comes with it is a wonder in Chines brevity and obscurity. It gives virtually nothing except a couple of confusing charts. Anyhoo, it being a more modern (?) rig I suspect it would work fine with a low impedance mike.

    Bottom line: What, if anything, do I need to do to use 500 ohm mikes with the Argonauts and the Xiegu?

    EuGene, KA5NLY
  2. KA5NLY

    KA5NLY Ham Member QRZ Page

    Does the following mean anything if I connect a 500 ohm dynamic mike into a transceiver (TenTec Argonaut) which calls for a high impedance microphone?

    "Low Feeds High
    In order to preserve signal level and frequency response, it's important to drive equipment with a source signal that is lower in impedance than the destination equipment's input impedance. If the input impedance of a device is not significantly higher than the source impedance, the signal will be reduced or “loaded down” and its signal to noise ratio and frequency response will suffer." Al Keltz
  3. W9WQA

    W9WQA Ham Member QRZ Page

    yes, right as i see it , if the output level from your "0ne" ohm mic is sufficient you are good..
    think about need certain volt level. the radio has no idea what z the source is...

    predict; you will see arguments longer than this page....
  4. KA5NLY

    KA5NLY Ham Member QRZ Page

    Of course the reason I asked is that the Ten-Tec manual specs page stated the mike needs to be of the high impedence ilk. That brought up some questions in my mind: (1) In spite of the "Low Feeds High" paragraph I quoted above, why must I use a high impedance mike? (2) how high is high - 1k? 10k? 100k? 1meg? (3) What deleterious effect will using a 500 ohm dynamic mike have on my signal strength and/or readability?

  5. KA5NLY

    KA5NLY Ham Member QRZ Page

    By the way, how does the voltage level of the 500 ohm dynamic element compare to the voltage level of the original ? ohm crystal element of the D-104? If there is a problem using the low impedance dynamic mike with a radio calling for a high impedence mike related to too low an output voltage of the former?

  6. KL7KN

    KL7KN Ham Member QRZ Page

    EuGene, both the Mike connector and the Key connector on the G1M have 3.3 VDC on them all the time power is connected - on or off.

    Don't know if that matters the D-104, but it might.

    I'll add this to the warnings section - still waiting for any additional comments on the draft before I put it to bed.
  7. KA5NLY

    KA5NLY Ham Member QRZ Page

    Dang! I guess I will need to get with some microphone guru to find out what cartridge I would need to put in a D-104 to attach it to a rig with the 3.3 VDC phantom power. That would seen to be an additional item to determine in addition to what impedance is needed.

    As for the impedance, I would think high impedance is what was needed for tube rigs, and somewhat lower for older transistorized gear, whereas today's rigs would work best with 100 -500 ohm mikes. Where is that mike guru when I need him the most?

    Strange that the voltage is on the key and mike connectors even when the power is turned off!! Wierd!

    The plot thickens.

  8. KL7KN

    KL7KN Ham Member QRZ Page

    Not weird, just a G1M. Now if the Vendor would release a set of technical drawings - say like Elecraft did for the KX2....
  9. W9WQA

    W9WQA Ham Member QRZ Page

    sounds like the 3 volts is keying voltage you need to handle,maybe block with a cap or use to key. . i dont know the rig but.
    "think about need certain volt level. the radio has no idea what z the source is.."
    "z" dont matter if you have the needed audio voltage.
    ill repeat, it could be a "one" ohm source !!!
  10. KA5NLY

    KA5NLY Ham Member QRZ Page

    OK, I will get my D-104 mikes rebuilt with 500 ohm dynamic cartridges, ignore the 3.3 volts, and plug 'em into the Argonauts and the Xiegu. The most that will happen is that nobody will hear me. EuGene

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