[ICOM] Digital Interface Problems

[gfiber at comcast.net]

Bob,

RFI intrusion. The audio input in the back, ACC ! jack,  is high impedance where the mic is 600 ohms. You may need to do some isolation work with audio transformers. Its quite common on the Icom products I cross that bridge hundreds of time when I worked for Icom.

Now also remember the mic element is hot, it is not switched with the PTT so having a mic plugged into the front of the rig while keying from the ACC 1 jack you will also pick any audio that is about in the shack.

Gary K8IZ. 

-------------- Original message -------------- 

> Any ideas what could be wrong here? 
> 
> I have interfaced my rig for digital operation as 
> described below and it seems all is well with one slight 
> problem noted at the bottom: 
> 
> SET UP: 
> 
> ----- 
> ----- 
> Rig control (COM 2): 
> Works great on all logging software. 
> 
> I am using a CT-17 with my IC-728 (same as the 729 w/o 
> 6mtrs) 
> Hooked up on COM 2 (9 pin serial). 
> I have the "PTT through Radio Command" (not selected). 
> "Allow external interrupts" (not selected). 
> "Radio PTT via Command" (not selected) 
> ----- 
> ----- 
> 
> ----- 
> ----- 
> CW keying (COM 1) 
> Works great with all logging software for CWkeying. 
> 
> Auto CW Keying of Rig (COM 1) "DTR=CW": 
> I made a little homebrew 9pin interface (limiting circuit 
> transistor ect in the jacket) so I am using with "DTR=CW" 
> hooked straight to my CW input jack at the back of the 
> rig. 
> ----- 
> ----- 
> 
> ----- 
> ----- 
> AFSK to rear panel (ACC1): 
> (NOW WE GOT TROUBLE) 
> I *tried* to hook the Audio up for the Digital Modes: 
> 
> 1) Went directly from the fixed audio output on the rear 
> of the rig to the audio input of the computer soundcard 
> for decoding. 
> (ADJUSTED/TESTED NO PROBLEMS DECODED ALL MODES WITH ALL 
> LOGGING SOFTWARE) 
> 
> 2) Setup DTR for PTT into ACC1 
> (ADJUSTED/TESTED - works great and keys the rig) 
> 
> 3) Went from computer's soundcard output to the rig's 
> audio input on the rear panel. 
> (ADJUSTED/TESTED - SEEMED TO WORK GREAT BUT WILL 
> EXPLAIN) 
> 
> 1) With the ACC1 plugged into the rear panel and the mic 
> plugged into the front panel through the external IC-1514 
> VOX BOX. A station on 20 mtr bpsk reported *very hot* 
> signal and spurs from my station on the band. So I made 
> further adjustments. He said it was not better. 
> So I QRT'd pending further investigation. 
> 
> 2) With the ACC1 jack still plugged into the back of the 
> rig and using the microphone on the front panel (properly 
> set for good audio), reports are that I am distorted so 
> much so - they don't even know who is calling them. 
> 
> 3) If I unplug the ACC1 jack the SSB audio distortion 
> immediately goes away and my signal is reported to be very 
> good audio quality. 
> 
> 
> 73 fer nw, 
> Bob 
> KE5CTY (old calls WB5ZQU - WY5L) 
> 10X# 37210, FP#-1141, SMIRK#-5177 
> http://www.qsl.net/ke5cty/ 
> Code may be taking a back seat for now, 
> but the pioneering spirit that put the code 
> there in the first place is out front of it all. 
> 
> 
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> ---- 
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