Programming Icom IC-H11 transceivers

Icom IC-H11 transceivers can be programmed without the EX-704, all you need is a computer and a 5V serial port.

Wiring

The flashing is done via the microphone socket. You need a 2.5mm stereo plug - the tip is RX, the ring is TX, sleeve is GND. TX can be used to verify programming.

Hold the CLONE button while turning the radio on, then release it after the beep, and starting the programming. The radio will beep twice if the programming is finished. You can check the programming by going into CLONE mode again and pressing the CLONE button again to have the radio transmit its programming for backup.

Protocol

The serial settings are as follows: 1200 baud, 8 bits, 2 stop bits, mark parity.

The data is in a packet type structure that lists the programming data per channel, and some write/end packets.

The frequency bytes are calculated by dividing the desired frequency in kHz with the channel pitch, 6.25kHz in my case. Non-accessible channels seem to be accepted, the PTT just does not do anything.

I did not decode any of the other parts of the packets because I do not care, it may relate to some of the call tones or something.

Channel packet

FE	05	01	Channel #	00	FD
FE	80	Frequency byte 3	Frequency byte 2	Frequency byte 1	Frequency byte 0	FD
FE	02	01	00	FD
FE	80	10	00	00	00	FD

Write packet

FE	02	08	00	FD
FE	81	00	FF	FD
FE	81	01	FF	FD

End packet

FE	80	20	00	0D	A0	FD
FE	02	09	01	FD
FE	F9	FD

Packet Order

Channel Packet 1

Write Packet

Channel Packet 2

Write Packet

Channel Packet 3

Write Packet

Channel Packet 4

Write Packet

Channel Packet 5

Write Packet

Channel Packet 6

Write Packet

End Packet

Software

I made a terrible Python script to program the radio, all that is required is changing the serial port and the frequencies.

Updated on 13.02.2026