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Amateur Radio Data Transmissions - For discussion of all modes used to send data such as APRS and packet.

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Old 01-12-2018, 9:38 PM
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Default 8-Pin to TRRS

Hey All, I'm working on a project for a dedicated APRS repeater, and I hoping to use an old Mic-less Azden 7000h I have sitting around doing nothing.

I would like to use it with a Mobilinkd TNC2, which means I need to turn the 8-pin into a TRRS connection.

I am a novice at making adapters, and was hoping that someone could help me figure out how I need to connect these pinouts.


PIN 3 -
PIN 6 COMMON GROUND (up/down etc).
PIN 8 + 13.8 VOLTS.

Mobilinkd TNC2
TRRS 3.5mm TRRS audio connector for Radio.
1. Tip = Speaker (audio input to TNC)
2. Ring 1 = PTT
3. Ring 2 = Mic
4. Sleeve = GND/Common

I see where PTT, MIC, and Ground would line up, but I'm unclear on how the "Speaker" input source from the 8 pin would be.

Any help would be appreciated.

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Old 01-12-2018, 11:05 PM
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First off, you'll need more than just the 8 pin connection for the TNC connection to work since it doesn't provide speaker audio. That will be available on the external speaker connection jack, but will at least force your connection to be more of a Y connection (TNC to both mic jack and ext speaker jack on the Azden).

From the TRRS:
1. Tip to the tip on the external speaker connection.
2. Ring 1 to pin 7 on the Mic connection
3. Ring 2 to pin 1 on the Mic connection
4. Sleeve to Pin 2 on the Mic connection (perhaps also to the sleeve on the external speaker connection, I say perhaps since both mic ground and speaker ground should be the same ground level in the radio).

An alternate way you may make the connection, but requires a minor modification to the Azden (and is how I have my old Azden 3000 connected to my TNC). Swap out the external speaker jack with a 3.5mm (1/8") 4 conductor switched jack wired up similar to the connections I indicated above. You can then just use a TRRS audio patch cord to connect the radio to the TNC. This is a bit more complex, but makes for a cleaner looking connection. The down side is you will no longer have an external speaker connection since doing so will short out the MIC and PTT lines and will lock the transmitter on, perhaps damaging the finals.

For the MIC connections on your modification, you can simply trace where they connect from the MIC jack on your radio to the board(s) in your radio (most should have external connections for them you can tap into). For the PTT connection, you can just use standard insulated hookup wire. For the Mic tap, you should use some shielded wire (perhaps from an old mono patch cord) and ground the shield on one side or the other (which side doesn't matter so just use the side where it's easiest to find a nearby ground connection). This should help prevent hum from being picked up on the transmit audio). Just a note, if your new jack has an easy available connection to the shield, that will make a good easy available ground connection.

Last edited by n5ims; 01-12-2018 at 11:13 PM..
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Old 01-13-2018, 7:06 PM
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Wow, very helpful. Thank you!
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Old 01-14-2018, 12:44 PM
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Got it all wired, works perfectly.
Thanks again.
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