[ICOM] Digital interface- no audio modulation problem on Icom 746Pro

[David J. Ring, Jr.]

The input on the 756 requires a MUCH larger input signal than the microphone 
signal.  I would suspect that this is the problem with the 746 also.  I know 
people who have sent a microphone level signal the the rear ACC jack on a 
'706 and it worked find.

The problem probably is that the 746 needs the "near line level" signal that 
the 756 needs on the back jack.

I don't know for sure as I don't have a 746, but I do know this is the case 
for a 756PRO.

73
David N1EA

----- Original Message ----- 
From: "James W. Long" <JamesLong at wowway.com>
To: <icom at mailman.qth.net>
Sent: Monday, May 22, 2006 7:21 AM
Subject: [ICOM] Digital interface- no audio modulation problem on Icom 
746Pro


Dear All

Help! is my rig blown?

I am having trouble with my digital interface.
 it is home made and extremely simple.

 this interface never "used" to work on this rig. this is the first time.
 FOR THIS RIG.
 this interface works PERFECT on a ICOM 706MKIIG and a Kenwood TM-V7.

 I bought this rig new, and parts of it are still unknown to me.
  have wired up a home make CIV interface and and
 amplifier interface and have it wired for audio thru a DSP
 and have it hooked up to 6M, 2M, 440 and HF Antennas.
 So I'm not lost or anything here. I just need some direction now.

 the problem:
  the PSK sound out from the computer is not modulating,
   all I see is rf, no carrier. with a second receiver
  used to back monitor my transmitted PSK I do not hear it
  except  way way way way way WAY WAY WAY
  down in the dirt so low it is almost indistinguishable.
 like crossover or induction or something. it is not strong. you
  would not hear it unless you were looking for it with all the
  volumes full up all the way in a quiet room.)

 I have verified FULL audio is present all the way up the cable
  and the computer volume is ALL the way UP.

 how its wired:
   PTT works perfect on HF and vhf.
   its a small transistor / diode / resistor circuit,
   which comes off serial COM1.
   it brings PIN 3 on DATA socket, PIN 3 on ACC2
   and PIN 6 on ACC2 to ground simultaneously as all these
   pins are wired in parallel. no matter what amateur band
   I go to, the Icom goes to xmit when I say so on the computer.
   so that's working perfect.

   audio (receive).
   I can receive audio fine. I see PSK signals in mixw2 in the waterfall.
   I can copy them fine.  the receive audio shares common ground
   between radio and pc sound input.  I don't want a discussion of
   this topic since its not the problem.   audio comes from
   DATA socket PIN 4 and PIN 5 which are wired together and then
   connected to the soundcard input with proper respect for polarity.

   Audio send (The Problem)

    Audio send shares common ground with the pc.
   no discussion wanted on that subject.
    the soundcard output has been traced all the way up the cable
    with headphones and I verify full signal is present at the radio 
receptacle
    where it plugs into DATA Socket and connects to PIN 1.

    for the Icom 746 pro I have only added the ACC2 Plug with pins 3 and 6 
wired
    in parallel to the five pin DATA Plug pin 3.


    I can successfully use this SAME cable into a Kenwood blue face TM-V7 
which
    has the IDENTICAL 5 pin DATA receptacle in the front on the left side
    and it works perfect. I use an adaptor into my 706MKIIG and it also 
works
    perfect.




  what is my problem? what did I miss? is the input circuit on the 746 pro 
blown?

  or is there some menu setting I need to make?  I try this on 14.070 USB
  with NB off no compressor just generic settings. voice works fine.
  I have made many voice contacts with this rig.

  I just cant get audio to go from the back of the rig into the inside of 
the
  rig. I still don't know everything about this radio so what am I missing?
  it will transmit PSK over the microphone when I wire sound out thru my 
speakers,
   but that is not the desired solution.  neither is interfacing to the mike 
input.


  do you think the input circuit (PIN 1 on DATA) is toast?


 Thank you in advance,
   KC8RYX James


----
Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
Icom Users Net: Sundays, 1700Z, 14.316 MHz
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