Connecting..... Welcome to the VE3MAL Bulletin Board. Dial in any time.

Add an Amplified Receive Antenna to the Icom IC-7300

RX Antenna Port Mod

I purchased an “RX7300” from a French ham on Ebay to add a RX antenna port to the IC-7300. It uses SMA connectors, and a little patch cable to bypass the RX antenna port when using a single antenna as usual. Install, was very easy, and required no permanent modifications or soldering. The only improvement I could see for such a kit would be to use a switch, or better yet, a relay, that can switch the RX antenna port on/off instead of using the awkward patch cable. However, for the price, I’m very happy with it.

Bias Tee Injector


Tx/Rx Switching the Bias Tee Injector

The Bias Tee needs to be powered only when the transceiver is in receive mode. This is accomplished by a fast (~1ms) reed relay connected to the SEND pin of the IC-7300. Circuit diagram This pin is normally used for controlling and amplifier, and is connected to nothing (floating) during RX, and goes to ground when transmitting. Using it with the 13.8v pin 8 gives voltage during TX, so the normally open pin of the relay can provide power during RX.

The circuit also includes TX and RX LED indicators, and a Zenier diode/Resistor combo to regulate the voltage down to 5.1v for the LNA. This is inefficient, but noise free, and since the LNA only uses ~30ma, little heat is dissipated anyway.

Low Noise Amplifier Powered by Bias Tee


Simple Rx Antennas