Image: Motorola Microphone Pin Checker - ZS1I
I have several Motorola Radios in my shack. Two Motorola Radios are currently being used for the GRHub Network. I am using AllStar Linux Software for my nodes. Setting up a Echolink as a radio linked node is fairly straight forward and you can use a soundcard interface between the computer and the radio. The GRHub Nodes on the other hand all run on Raspberry Pi's fitted with Soundcard Fobs between the radio and the Pi. I use the COS/COR function which necessitate modifications on my older Motorola Radios. Because of the older radios I cannot use the back accessory connector except the speaker output. I use the RJ45 8 pin Microphone connector (Jack) on the front of the radio for COS/COR, PTT, AUDIO etc. When you modify the Motorola for the COS/COR you need to wire Pin 8 on J8 of the logic board connector and Pin 1 on the microphone socket. (connector) I used a multi-meter to check the pins to ensure that I solder the wires to the correct one. This is a tedious task as my eyesight is bad and you need to fabricate a wire connection to the multi-meter lead points. You can check the pins on the inside of the radio but then you need to loosen the microphone board connector etc. Too much of a schlep!
When I did the CTCSS Mod on the microphone/volume connector board I came up with an idea to easily check the pins for connectivity and that I use the correct pins on the microphone. If you do this incorrectly it will surely damage your radio. So you must ensure that you use the correct pins for both modifications.
I used a short piece of Ethernet cable to which a RJ45 is connected on the one side. I removed the shielding on the other side to expose the wires and numbered them according to the Motorola Mic Connector Socket. I call it "The Motorola Mic Pin Checker Gadget". Once you double checked your numbering you are ready to check the pins for connectivity in both the modifications I described above. It is as simple as using a multi-meter set to the connectivity setting. Take one probe of the multi-meter and put that on the pin of the logic board and the other probe to the "Motorola Mic Pin Checker" wire number. Example: I use Pin 1 on the microphone socket and Pin 8 on the logic board. If you get the beep sound you know that your connections are correct. IMPORTANT: Double check your mods before adding power to the radio and switch on.
Image RJ45 Jack - Repeater Builder
Image: Logic Board J8 showing pin 8 - Repeater Builder
Both the GRHub Network Motorola radios Mic Connections now work as follow:
This simple "gadget" has saved me valuable time and is easy to use especially if your sight is not that good anymore. This "gadget" can also be used for other radios that use RJ45 connectors. PLEASE check your radio's owners manual for the microphone pin outlay. All radios do not have the same microphone pin outlay!!
Finally: For me this "gadget" is surely a useful addition to my test bench. I hope this idea can assist other radio amateurs when making modifications to your Motorola radios.
