Information on interfacing the WB2REM/G4CDY AMI-2 Interface to a Motorola GM300 radio for use on Echolink
I was helping a fellow ham figure out why he was experiencing a very low audio output from the Motorola GM300 Link radio and AMI-2 Echolink interface he was trying to set up.
This is how I fixed the low audio, built the interface cable and setup the radio and computer.
Parts:
I used the 16 pin Accessory connector on the rear of the GM300 Radio.
Plugs can be made easily by purchasing the connector body and contact pins from manufactures like Digikey or Mouser or pre-made from sellers on ebay.
Here are some part numbers.
Digikey:
Connector body, with locking tab, 16 pin: 104422-1-ND
Contact: A3007-ND
Mouser:
Connector body: 571-1044221
Contacts (pack of ten): 571-1873093
You will need 5 leads coming out of the accessory connector. (Optional 7 leads)
Wire up the plug to pins 2,3,7,8&11. (Optional wire pin 15 to 16 for internal speaker)
You will also need 4 (Optional 5) 1/8 mono cords to plug into the interface.
Radio shack part #
42-2434 works well or you can make your own.
And you will need 2 1/8 double male stereo cords to go between the Computer and the AMI-2 Interface, as well as a Straight through DB9 serial port cable.
Wiring the Accessory plug:
PTT - Connect the center wire of the mono cord to Pin 3 of the Accessory plug
COS - Connect the center wire of the mono cord to Pin 8 of the Accessory plug
*Note Pin 8 may need to be configured for COS by programming the radio.
MAIN RX - Connect the center wire of the mono cord to Pin 11 of the Accessory plug
RADIO MIC - Connect the center wire of the mono cord to Pin 2 of the Accessory plug
GROUND - Connect the shielding of cords PTT, Main RX, & RADO MIC to Pin 7 of the Accessory plug.
For more information about programming the radio
NOTE:
As long as the microphone is inserted and hung up on the clip, the PL will be enabled.
To operate the node without a microphone plugged in, make an RJ45 mic plug shorting the PL line (PIN 3) to ground (PIN 4).
To enable the front panel speaker, jumper 15 to 16 on the rear accessory plug.
CONNECTIONS:
Plug the COS, PTT, MAIN RX, and RADIO MIC plugs into the AMI-2 Interface.
Attach the Serial cable from your computers Com port to the AMI-2 Interface.
Attach the Stereo plugs from the Computers sound card to the AMI-2 Interface.
Plug in the power connector.
Download Echolink and run the Sysop Wizard
Make sure in Sysop Setup / RX CONTROL, you check off Serial CD.
TX CONTROL is ASCII Serial (Don't check off 9600)
OPTIONS Make sure MAX KEY DOWN TIME is set. (i.e. 300 seconds)
LOW AUDIO SOLUTION:
I experienced a VERY low audio output signal on my first attempt.
I verified all my audio settings and still low audio from the link.
After some troubleshooting and research I contacted Jim WB2REM for a possible solution. He suggested I jump out the Two 100 K resistors @ R20 and R21.
This interface board was designed to work with Amateur Transceivers, Which have different microphone impedance that the Motorola's.
Once I removed the 2 resistors and added a jumper wire in their place my audio level was improved drastically.
I also needed to use a stereo cable from the Speaker output of the sound card to the Sound card speaker jack of the AMI-2.
FINAL SETTINGS:
Connect up to the Echolink Test Server, which is node number 9999, and adjust your transmitted and receive audio on your sound card.
HYPERTERMINAL INFO:
You may need to change some settings in the PIC of the AMI-2 like TX TIMEOUT and COS POLARITY. More info is available in the FILE section of the AMI-2 Yahoo group.
It should also be in the documentation you received when you purchased the AMI-2.
I hope the information I put together helped you out.
This was my first experience with the AMI-2. I have or had owned the Original
WB2REM Interface board, The Original AMI, and the ULI board.
I'm currently running
EchoIRLP on my repeater system and that uses the
IRLP interface board.
Links to places mentioned in the article & places where I found more information
