Cable for MFJ 9406

I’m going to set up a Digirig Mobile - Logic Levels (default) device on a analog MFJ 6 meter transceiver. It has a 4 pin microphone din connector (similar to a cb mic pinout). It also doesn’t have aheadphone jack so I’ll be adding that. There is also an amp keying circuit on the rear. Are there any wiring diagrams for similar setups or harnesses I can modify?



From the pics online it looks like the MIC is a regular DIN 5 and the headphones is 6.5mm jack.

The audio cable to Digirig would look something like this:

DIN5 pin 1,2,5 (Ground) → 3.5mm TRRS sleeve (GND)
DIN5 pin 3 (PTT Line) → 3.5mm TRRS ring2 (RIG_PTT)
DIN5 pin 4 (Mic Line) → 3.5mm TRRS ring1 (RIG_AFIN)

6.5mm TS tip (HP) → -> 3.5mm TRRS tip (RIG_AFOUT)
6.5mm TS sleeve (GND) → -> 3.5mm TRRS sleeve (GND)

You can start with any existing Digirig cable that has headphones tail and replace both transceiver side connectors to match the radio.

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Thanks for the pinout diagram and suggestions. Receive works great but when I plug in the 5 pin din and transmit it works correctly (both RTS and VOX work) but after transmitting the receive level is pegged in WSJT-X and there is a hash on the waterfall. Is this a ground loop issue?



Tried an isolation transformer on the receive line and it seems to have fixed the problem!

SO one more concern- I think I’m drastically over driving the mic input at the transceiver with the line-in voltages. Transceiver has no line-in port. Is there a simple way to attenuate that line with Digirig or should I just build a small attenuator between Digirig and the transceiver?

@KC9OJV How did you do the isolation transformer? Ferrite bead(s)?

73 Constrainted

I would first try the sound level adjustment sliders available in mmsys.cpl for the Digirig audio output , but maybe you already have done that.

73 Constrainted

Thanks for your comments- yes slider turned down. From what I’m reading dynamic mic inputs expect just a few mv’s and line-in can be almost a volt so lots of attenuation is called for here I believe.

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How did you do the isolation? Optical?

73 Constrainted