This is an automatic antenna switching project that connects directly to the accessory jack of your IC-7300 radio. It’s currently a project under development.

I recently parted ways with my IC-9100 which had served me well for the best part of a decade, and in that time I’d taken the 2 HF antenna jacks for granted. As someone who spends a fair bit of time on 6m, the thought of a clunky coax switch, along with all the pitfalls of inflexible cabling made me think there was a better way, and in my opinion, this is it.

It’s an Arduino controlled switch that measures the band voltage on pin 5 of the IC-7300 accessory jack. It’s self powered from the switched 13.8v supply on pin 8, and has a TX lock so there’s no chance of switching antennas during transmission.

It has two modes selected by an external switch. HF and 6m, or every band.

The board has individual output pins for bands 6m through to 160 meters. Be aware that Icom has grouped 15 and 17m bands  together as well as 10m and 12m. These outputs go high (+5v) or low depending on what band you have selected on the radio and are designed to drive readily available relay boards that are available as single relays up to banks of 8. These relays can then be configured to switch coaxial relays.

The IC-7300 can deliver up to 1 amp at 13.8v via pin 8 on the accessory jack. If you’re running just one external relay like I am for 6m then you can utilise this supply for an external relay. Don’t forget to use a flyback diode such as a 1N4001 across the coil. Be careful if you go down this path. It’s at your own risk as anything you plug into an expensive radio may have unwanted consequences.

The project can use a standard 20×4 or 16×2 LCD display which is switchable in code. The band voltage displayed may vary from radio to radio so further investigation is required.

An Antenna Relay

This is a 500w relay I’ve had in the junk box for many years and what I now use to switch between my HF and 6m antenna using the 6m output on the PCB via a 5v optoisolating relay. It’s located over a metre away from the PCB which makes cabling up super easy.

The uses of this project are up to your creativity as every band has its own output pin. You could use it to switch anything that’s band specific.

A byproduct of this project is a breakout board for the IC-7300 accessory jack. It makes is super easy to get signals in or out of your radio. Watch this space for updates.

PCB Layout

How it works

Connection to the IC-7300 is by a commercially available 13-pin male-to-male connector. The PCB is powered by the radio. Two voltage dividers feed A0 and A1. A0 measures the band voltage on pin 5 of the accessory jack and A1 senses TX from pin 3.

Depending on the band selected on the radio, the output pins on the PCB will be either high or low accordingly. Each band has an output to drive a small 5v relay such as this Arduino Compatible 4 channel 12v relay from Jaycar. In turn, this can be used to drive anything you like such as a high-power coaxial relay.

The board has a 4-pin header, marked IC-7300, that allows easy access to the signals from the marked radio pins, 2, 3, 5 and 8 for expansion as you see fit. For example, you could use pin 3 and ground to connect a foot switch or take the 13.8v to power a device, such as a light in a power meter on an external preamp.

The power header pins can be jumpered so the device powers on and off as the radio does, or you can bring it to an external switch if required. The 13.8v header supplies volts from the radio. It can be used to power low-current devices. Keep in mind the radio supplies a maximum of 1 amp. See page 18-2 of the IC-7300 manual.

The LCD header connects to a standard 2 or 4-line LCD with an I2C serial interface. There is also a mode header for a SPST switch used to switch between ALL BANDS or 6m/HF. You could run an external switch or jumper it according to your needs.

You may also notice a provision for D4 and D5. These are unused outputs of the Arduino and are on the board for future updates as the project evolves.

These fully built and tested boards may be available from time to time in the VK3FS shop. If you don’t see any in stock, contact me and I may be able to help based on parts availability.