To interface the Codan 9350 auto antenna tuner to an ICOM 706 couldn't be easier. Literally just plug it in to the connector on the back of the Icom.

The first interface shown is the wiring between the connector on the 9350 and the 4 pin Molex connector on the back of the Icom. No additional components are required.

The Tune button on the radio will activate the tuner as required and the radio will stay on TX at 10 watts until the antenna is finished. I think there is a time out period if the antenna cannot make tune. There may occasionally be an RF feed back problem with the radio and a small cap i.e. 0.1 uf ceramic can be placed from pin 1 to pin 4 on the back of the ICOM.

PTT tune can be set ON in the start up menu of the radio if you wish. Although I have not tried it this, the interface connection should also be the same for ICOM 746 and others.

More advanced interface using the scan preamp function in the 9350

It seems a shame that there is a very nice preamp in the 9350 which is ideal if you want to use the ICOM as a general coverage receiver out side amateur bands. Since you cannot transmit out of band to tune the antenna the preamp becomes very useful. Additionally if you are scanning memories or just flicking around the bands just listening from band to band there is no need to tune the antenna for each band change. With the preamp ON the receive performance is about the same as when the antenna is resonant.

With the interface below you can set the preamp on by closing or momentarily closing the mute on the radio. The low signal on pin 13 sets the latch IC1 and the preamp is ON. (The 9530 does a little tune setup for preamp) Flicking the PTT on the mike or pushing the tune button clears the latch turns OFF the preamp and sends the 9350 to tune up as per normal operation.

I have noticed on my 706 that if I have un-programmed channels and I rotate the memory step knob past them the radio pulses a mute close output on the blank channels. This also has the affect of setting the 9350 into preamp ON mode.

I put the 74HC74 on a small piece of vero board and placed it in a plastic jiffy box. I used a normal five pin din connector to connect to the 9350 and the ICOM supplied 13 pin plug with the small wiring tail. The colours quoted are the ones for the supplied plug.

As an additional feature there was plenty of room to put two RCA connectors on the jiffy box. These provided and easy connection to the AF IN/OUT functions from the ICOM. This allowed easy computer interface to the radio if I wished to use it. These have nothing to do with the operation of the auto tuner.