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Re: Fixed level audio too low on data port?

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  • Scott Townley
    Good point Joe...that would do the trick too. BUT...two things to be aware of: 1. The typical soundcard microphone input is setup for an electret mic. So
    Message 1 of 5 , Feb 1, 2004
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      Good point Joe...that would do the trick too.
      BUT...two things to be aware of:
      1. The "typical" soundcard microphone input is setup for an electret
      mic. So the stereo plug is wired thus: tip=mic input, ring=electret
      bias voltage (typ. 2-5V), sleeve=ground. When hooking up to your
      speaker/aux audio out, you will very much want to use a MONO plug at
      the mic input of the soundcard. This externally shorts the electret
      bias voltage (there's an internal current-limiting resistor in the
      soundcard, so no worries there) and keeps it out of your radio. Maybe
      all audio outputs are AC-coupled but I wouldn't count on it... :-)
      2. Double-check the output impedance specification of your audio
      source. The "packet", fixed-level outputs should be OK since they're
      generally rated at 10koh out. However, using an audio output designed
      for minimum distortion at 4-32 ohms (e.g., speaker output) may give
      poor results, as the distortion and bandwidth characteristics of the
      audio source may be quite different when driving the 10koh-30koh
      impedance of the mic input.
      Not that not heeding these two points will yield poor results, but
      things to consider in the interfacing.




      --- In FT100@yahoogroups.com, "Joseph A. Counsil" <counsil@r...> wrote:
      > Hello,
      >
      > I experienced the same low audio level problem while using WSJT
      > software (but NOT with MixW, HamScope, MMSSTV, etc.). My solution is
      > that while using WSJT, I feed the audio into the MIC input on the
      > sound card, rather than the LINE input. The MIC input sensitivity
      > (input gain) is much higher, and I have plenty of head room for input
      > level adjustment. I'm running an old ISA Sound Blaster-16 sound card.
      >
      > 73,
      > -Joe-
      >
      > --- In FT100@yahoogroups.com, "Scott Townley" <nx7u@a...> wrote:
      > > Hey Bruce,
      > > It occurs to me that the 6-pin miniDIN "packet" interface is
      > > standardized, actually.
      > > I have two other radios with the same capability, and the 1200bps
      > (pin
      > > 5, used for AFSK) port on all of them are specified 300mV/10koh.
      > > Since the FT-100 manual gives 2 "votes" to 300mV/10koh and only 1
      > > "vote" to the other, I am pretty confident that the 300mV/10koh
      > answer
      >
      > ........
      >
      > > > results are the same. Setup is working and have made several
      > mobile
      > > > FSK441 qso's now but the low audio is bugging me. TX audio level
      > into
      > > > port appears fine and getting good signal reports.
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