Yaesu FT-857D + Digirig: CAT works, but no audio from DATA port

1

Hi everyone,

I would like to ask for some advice before I conclude that my FT-857D may have a hardware issue. I have done quite a lot of testing and measurements, so here is a detailed summary of what works, what does not work, and what has already been verified.

What works correctly

1. CAT control works 100%

Connection:

FT-857D ⇄ Digirig Mobile ⇄ PC

CAT control works perfectly in:

  • FLRig

  • JTDX

  • WSJT-X

  • Logger32

Current CAT settings:

  • Menu 019: CAT RATE = 38400

  • Menu 020: CAT/LIN/TUNE = CAT

So CAT communication is definitely not the issue.

2. Digirig USB audio codec works correctly

In Windows, the Digirig is detected correctly as:

“USB Audio Device”

3. PC, Windows audio, and JTDX audio path work correctly

I performed a test by connecting:

FT-857D Headphones output → Digirig Audio IN

Result:

  • JTDX waterfall immediately shows signals

  • JTDX decodes stations normally

So this confirms that:

  • Digirig audio input works

  • Windows audio settings are correct

  • JTDX audio settings are correct

  • The problem is not on the PC side

FT-857D settings

Current radio settings:

  • MODE: DIG

  • Menu 019: CAT RATE = 38400

  • Menu 020: CAT/LIN/TUNE = CAT

  • Menu 036: DIG DISP = 0 Hz

  • Menu 037: DIG GAIN = 50

  • Menu 038: DIG MODE = USER-U

  • Menu 039: DIG SHIFT = 0 Hz

  • Menu 040: DIG VOX = 0

Additionally:

  • CW filter = OFF

  • SSB filter = OFF

  • DSP = OFF

  • NEDSP-1901-KBD module = OFF

What does not work

RX audio through the rear DATA connector

Connection:

FT-857D DATA mini-DIN → original Digirig combined cable → Digirig Audio IN

Result:

  • No waterfall activity in JTDX

  • No decoding

  • No audio input visible in Windows

Hardware verification already performed

1. Cable continuity test

I checked the original Digirig combined cable with a multimeter.

Result:

  • All wires have continuity

  • Audio wire goes from the mini-DIN connector to the 3.5 mm plug

  • Audio OUT is connected to the Tip of the plug

So the cable is not open.

2. Oscilloscope measurement – reference test using headphone output

Measured at:

FT-857D Headphones output

Using a FNIRSI DPOS350P oscilloscope.

Result:

A strong audio signal is clearly present.

Measured approximately:

  • +6.42 V

  • −5.95 V

So audio definitely exists in the radio.

3. Oscilloscope measurement – DATA audio path

Measured at:

3.5 mm audio plug of the original Digirig combined cable

Connection:

FT-857D DATA OUT → Digirig cable

Result:

At normal oscilloscope settings, I only see a flat line.

Only at very high sensitivity:

  • 2 mV/div

  • 20 µs/div

I can see very small peaks of approximately:

±2 mV

This looks more like noise or crosstalk than real AF audio.

I would expect tens or hundreds of millivolts if a real audio signal were present.

At this point I would really appreciate any ideas or suggestions from other FT-857D or Digirig users before I assume there may be a hardware issue with the radio.

Thanks very much and 73! Tomas

2

Pretty thorough investigation. The ultimate test is scoping the MiniDin6 directly on the radio to see if there is output at 1200 baud or 9600 baud pins.

3

Thanks for your suggestion.
Just to clarify — when you say to scope the MiniDIN6 directly on the radio, do you mean checking the DATA OUT pins while the radio is in modes other than DIG as well (USB, LSB, FM, etc.), or with different DATA port related menu settings? I already tried DIG and PKT, but maybe I am missing some specific configuration.
So far I checked both the 1200 baud and 9600 baud DATA OUT pins directly on the FT-857D connector against GND while tuned to 14.074 MHz, and I did not see any clear audio waveform — only very small spikes/noise around ±2 mV.
What also seems strange is that the radio does not appear to process audio on DATA IN during TX either. I will scope the cable and the DATA IN pin next to verify that the audio from the interface is actually reaching the radio during transmit.
One important detail: some time ago I installed a bhi NEDSP-1901-KBD inside the radio.
My first thought was that I might have accidentally affected the RX audio path during that installation. However, if both DATA OUT (RX) and DATA IN (TX) appear affected, that seems less likely to be a simple hardware issue, since I would not expect one modification to damage both independent RX and TX audio paths at the same time.
So at this point I am starting to suspect a configuration/routing issue rather than a hardware failure — but of course I want to verify it on the scope first.

4

One more update: I tried calling CQ on 7.074 MHz, and according to PSK Reporter, I’m being received nicely across Europe.

So the issue is clearly only in the RX path.

It is possible that something went wrong during the installation of the NEDSP-1901-KBD Noise Reduction Module.

At this point, I really can’t think of anything else. I have not found any menu setting in the Yaesu FT-857D that could disable the AUDIO OUT signal on the DATA connector.

5

I don’t have this radio, but my expectation is that the received audio should be present on the accessory port regardless of the selected mode. If you suspect that this is subject to the settings then see what specific values are used in digital modes - there are numerous videos on the subject.

6

Thank you, Denis, for your help.
Based on the troubleshooting I carried out over the weekend, I have come to the conclusion that there is a 99.9% chance this is a hardware issue with my Yaesu FT-857D.
After carefully studying the FT-857/FT-857D Technical Supplement schematics, I confirmed that the audio signal for the DATA connector is routed through the same section of the circuit where I previously made modifications during the installation of the BHI NEDSP-1901-KBD Noise Reduction Module.
I now strongly suspect that the signal path may have been disrupted somewhere in that area.
I will try to verify this during the week.

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