Part of our The Icom IC-7300 Mark II: The Complete Guide.
The Mark II added dedicated RX antenna in and out connectors, separate from the main transmit antenna port, which opens up receive-only options that weren’t as clean to implement on the original.
What these ports actually do
Rather than splitting your main transmit antenna line to insert a receive-only accessory, the Mark II gives you a dedicated path just for receive processing. Signal comes in the RX ANT IN port, passes through whatever external device you’ve connected, and returns through RX ANT OUT, all without touching the transmit path at all.
What you can actually put in that path
A receive preamp for weak-signal work on a quiet band, a bandpass filter to knock down strong out-of-band signals before they reach the receiver, or a noise-canceling device that needs a dedicated receive antenna to compare against. Since transmit never routes through this path, there’s no concern about accidentally keying up through a receive-only accessory not rated for RF power.
Why this is safer than the old workaround
On radios without a separate receive path, adding an external preamp or filter usually meant a relay or manual switch to take it out of the circuit before transmitting, since most such devices can’t handle transmit power. The Mark II’s dedicated ports remove that failure point entirely, there’s nothing to forget to switch out before keying up.
Setup notes
- Confirm your accessory device is designed for a receive-only signal path, not general antenna switching.
- Keep the wiring between RX ANT IN and OUT clean and properly shielded, same as any other RF connection.
- Test with the main transmit antenna disconnected first to confirm the receive path alone is working as expected.
It’s a niche feature for most casual operators, but for anyone running a receive-only accessory, it’s a meaningfully cleaner and safer way to do it than the workarounds required on earlier radios.