Some Icom transceivers have a function called “External Keypad.” This is a convenient function to select memories, such as CW messages, SSB/AM/FM voices, and RTTY and PSK messages with a homemade keypad connected externally.

Some amateurs are reluctant to make something themselves, but the only necessary parts are switches, resistors, plugs, jacks, a few cables, screws and a case. All you have to do is simple case building, parts mounting, and soldering. No power supply is required.

Figure 1. The completed external keypad

What is the function of the External Keypad keys?

Icom transceivers have 4 or 8 memories, depending on the model, in which the messages you want to send are stored. CW, SSB/AM/FM voice, and RTTY and PSK messages can be stored in those memories, and the contents can be sent by pushing the memory switch. Therefore, it is a convenient function for contests and portable operations.

Let's take a look at the circuit diagram

This time, we will build an external keypad exclusively for the IC-705. The circuit diagram is shown in Figure 2. below. Please refer to the "Connector Information" page of the IC-705 instruction manual for this circuit diagram and its operation.

Figure 2. Circuit diagram of the external keypad from the instruction manual of Icom IC-705

Let’s arrange the parts

Figure 3. below shows the necessary parts, as shown in the circuit diagram. The circuit is composed of switches S1 to S8. The required switches are called "momentary switch," which turns ON only when pushed and returns to OFF when released.

The external keypad also has a jack for the CW paddle so that you can use it with your usual CW paddle.

Figure 3. Parts list

Building the external keypad

Assuming that the IC-705 will be used in the field, I chose the smallest possible case so that it would not be bulky to carry. Also, I chose a switch with a large button so that you can easily see the switch number and activate it with the touch of your finger. In addition, the switch is physically strong, considering that it is used a lot in calls such as pile-ups, as you push the button many times.

If you print M1 to M8 on the completed external keypad with a lettering sticker, it will be even cooler!

Figure 4. Parts are installed on the universal board.

Figure 5. Completed external keypad

Turn ON the external keypad function in the IC-705 settings

Before you insert the stereo plug of the external keypad into the key jack of the IC-705, you need to select “External Keypad" in the SET mode in the IC-705. The following is an excerpt of the contents described in the IC-705 instruction manual.

Figure 6. How to set IC-705 required when connecting an external keypad

You can also connect your usual CW paddle to the jack on the side of the keypad case.

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