Monday, 22 June 2009 21:48
Comet SB-15 Antenna
2.15/4.5/7.2dBi (6m/2m/70Cms)
Codan 9350 Autotune Antenna
1.8 to 30 Mhz
Yaesu FT100D
HF, 6m, 2m & 70cm
Interface Design

The interface I am working on is based on a 16F84 PIC Microcontroller and two relays.  

The PIC provides the data conversion between the FT-100D's control messaging and the Codan 9350 Autotune control lines.

Pressing the tune button on the FT-100D will cause the radio to switch to CW and TX an output of 10Watts.   This will terminate when the Codan 9350 Autotune antenna responds with a 'Tuned' indication or if the tune button is pressed again before a successful tune cycle is completed.

Upon tune termination, the radio will revert back to the original mode and original power setting automatically.

When the radio reports that it has been set to the 6metre mode, the interface will activate Relay 1 and Relay 2, thereby switching the 6m RF path to the Comet CM-15 Antenna.


I have a Yaesu FT-100D which I want to interface with two antennas; an autotune antenna covering all of HF and another to cover 6m, 2m and 70cm.

Although the Yaesu ATAS-120 Antenna has been designed for use the FT-100D and will cover this entire frequency range, I want a more efficient, durable and rugged antenna system that will allow me to use the equipment in my 4x4 vehicle in rough terrain.

The antennas I have selected are a Codan 9350 Autotune whip and a Comet SB-15 6m, 2m and 70cm stainless steel antenna, which has some gain on each band.   I plan to mount the tribander on a roof rack mount in the middle of the roof and the Codan antenna will be able to be mounted either on the front bullbar of the vehicle, or at the rear of the vehicle on a specially designed mount.

The optimal location for the Codan 9350 antenna is on the front of the vehicle, however new regulations in Victoria prevent the use of antennas greater than 30mm in width being mounted on the front of the car.  

This forces me to have a rear antenna mounting point for use within Victoria and the bullbar mount for use elsewhere in Australia.   (Another great example of bureaucrat imposed regulations that don't make sense).
Schematic Diagram

More on the way.....

Bandsplit Problem

The problem with interfacing these antennas to the FT100D is that the radio has two RF outputs which don't align with the coverage provided by these antennas.   The first RF port covers HF to 6m and the second covers 2m and 70cm.

This means that the 6m band RF output needs to be 'shifted' from the HF RF Port to the VHF / UHF RF port.

I am working on a diplexer approach to interface the radio to the antennas but at the same time I'm investigating using a homebrew PIC controlled interface module for the task as well.

The advantage with the PIC based interface is that it will have a dual role in that it will also convert the control signals from the FT-100D and activate the autotune capability of the Codan 9350 antenna.

The convential approach to connect a Codan 9350 to an FT-100D is to use something like the 'Yaesu Tune Control' interface from   I know some local hams that use this configuration and they love it.
The 'yaesu-tune' is a very cost effective way to interface autotuning antennas to the FT-100D
FT-100D Active Interface
for the
Codan 9350 and Comet SB-15 Antennas
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