IC-7300MK2 | Radio setup guides

Connection

Connect the rear USB Type-C to the PC with a data-capable cable. USB carries CI-V and TX/RX audio; no separate audio interface is needed. Use the official driver supporting IC-7300MK2. Two virtual COM ports appear: A/B. Start with IC-7300MK2 Serial Port A (CI-V).

Radio settings · AFSK

Open MENU → SET → Connectors. Check TX audio under MOD Input and RX audio under USB AF/IF Output. ACC and USB output settings are separate. USB input here means audio via the connector, not USB sideband.

Item	Setting / check
Mode	Start with LSB-D: SSB Data, not the radio’s native RTTY mode.
MOD Input → DATA MOD	USB: shared by LSB-D/USB-D. Factory default is USB, but check for changes from presets or earlier use.
MOD Input → USB MOD Level	Keep the working FT8 value first. Factory default: 50%. Adjust with PSRTTY TX volume.
USB AF/IF Output → Output Select	AF: sends received audio to the PC.
USB AF/IF Output → AF SQL	OFF (OPEN): prevents radio squelch from cutting PC audio.
USB AF/IF Output → AF Output Level	Keep the working FT8 value and check PSRTTY RX level.
CI-V → CI-V Address	Factory default: B6h. Match PSRTTY to the actual radio address. If changed to 94h for another app, match PSRTTY rather than resetting it unnecessarily.
USB (B) Function	No change needed for Port A. Select CI-V only when also using Port B for CAT. The default RTTY Decode outputs the radio’s decoded text; it is not CAT control.
USB SEND/Keying → USB SEND / USB Keying (RTTY)	CAT PTT in this guide does not use DTR/RTS SEND or FSK keying. Set OFF unless needed for another dedicated use.

FSK keying transmission · Ver1.18

Example: DTR for FSK and CI-V/CAT for PTT. Adjust settings to your wiring and selected signals.

Serial keying for TX; Audio IN for RX. Neither primary nor secondary Audio OUT is used. Check radio RTTY mode, 170 Hz shift and Mark frequency. Keying polarity is independent of RX inversion.

Connect the radio to the PC with one USB cable to use FSK. See FSK keying output for the radio settings.

Radio settings

Radio item / connection	Setting / matching
USB Keying (RTTY)	USB (A) DTR / USB (B) DTR
USB Keying (CW)	OFF
USB SEND	OFF
Operating mode	RTTY / RTTY-R
RTTY shift	170 Hz
RTTY Mark frequency	2125 Hz

For radios with A/B ports

Shared CI-V port	USB Keying (RTTY)
A	USB (A) DTR
B	USB (B) DTR

A/B identifies a port; DTR/RTS identifies its line. When sharing CI-V, select the same A/B side for USB Keying (RTTY). CI-V on B depends on the model/port-function setting. The original IC-7300 has no A/B choice: select DTR/RTS only.

Keying polarity mapping

PSRTTY inversion	DTR OFF	DTR ON
Not inverted	Mark	Space
Inverted	Space	Mark

This table maps PSRTTY control signals. It is independent of A/B selection and RX decoding inversion. Start without inversion, then match the radio/interface polarity.

Manufacturer reference: manual / USB port settings (IC-7300MK2)

If FT8 already works

With FT8 in USB-D, LSB-D uses the same DATA MOD and USB MOD Level. Check actual LSB-D after PSRTTY connects and keep input/gain first. Plain USB uses DATA OFF MOD; check DATA MOD separately for LSB-D.

PSRTTY settings · AFSK

Select IC-7300MK2 and CI-V CAT PTT. Start with the Serial Port A (CI-V) COM and explicitly choose the same MK2 USB audio device for Audio IN/OUT. Start with LSB-D. Match any changed CI-V address, such as 94h. Close other apps using the same COM.

No modulation

Compare FT8/PSRTTY outputs → check actual LSB-D → DATA MOD = USB → USB MOD Level and PC/PSRTTY TX volume. For CAT failures, first check the Port A COM and CI-V address. Port B requires USB (B) Function = CI-V. FT8 over LAN uses a different audio path; do not treat it as this USB connection.

Official sources

Based on official IC-7300MK2 documentation. Menu names/positions may vary with firmware or language.