Icom External Keypad

In the past I’ve designed and built external keypads for triggering the REMOTE input on an Icom mic connector [1] & [2].  These both were designed to add an auto repeat feature to the in-built Icom voice keyer for older radios by monitoring the radio’s PTT state (the duration of the voice recording) then adding a user defined delay before sending the next voice.

However more recent Icom radios have the feature of auto repeating a voice keyer memory built in, so all the extra circuitry, and PICAXE control PIC is not needed and a simple keypad is sufficient as a short press on the M1 to M4 button triggers a single voice keyer send, whereas hold the M1 to M4 button for a second enables auto repeating of sending voice keyer memories, the delay etc being defined in the Icom menu settings.

The M1 to M4 buttons work by presenting a unique resistor value to the REMOTE pin on the Icom mic connector, as shown below.

4 Button Icom External Keypad

Looking at button options I found a 4 button membrane, and it was available for a low price on eBay and many other outlets.  These have 5 connections, 1 common wire to each button and 1 wire from each button, a total of 5 wires, which allows the circuit shown above to be wired.

Boxing

The main construction is to make a long thin opening in a box to allow the ribbon cable through.  First thing is to mark where the keypad membrane will go and where the ribbon cable will go through the box.

Then, using a routing bit in the drill, a slot is made that the cable fits through.

Internals

Then a small PCB with the required resistor values to be installed, I used SMD resistors but through hole will work to.  A 5 pin header (dupont connector) to attach the ribbon to the PCB.

A 3.5mm connector is fitted on the back of the box to connect to the Icom Mic connector, then the ribbon cable is coiled up before the cover is fitted.

Voila, a decent looking Icom voice keyer keypad is finished.

So good in fact, I made 2!