FT-920 + SCU-17 connections and settings

Yaesu FT-920 connexions with Yaesu SCU-17 for AFSK mode / RTTY, WSPR, FT4/FT8, etc.

Pin 1 (AFSK Input): Connect this pin to your TNC’s “AFSK Out” or “Mic Audio” output line. The optimum input level is 30mV rms, and the input impedance is 3 k. Your TNC’s audio output level potentiometer will allow you to set the level to the optimum value. This pin may be used either for 300 baud SSB-mode digital operation or for 1200-baud FM packet. The bandwidth and frequency response are not, however, suitable for 9600 baud operation. Be sure the AFSK-FSK switch on the rear panel is in the AFSK position. For FSK operation (whereby the TNC closes a line to ground to accomplish teletype keying), set the AFSK-FSK switch to FSK, and connect your

TNC’s FSK keying line to Pin 1.

Pin 2 (Ground): Connect this to the shield(s) of the cable(s) used for connections between the TNC and the FT-920.

Pin 3 (PTT): Connect this pin to the PTT line from the TNC. This pin, when grounded by the TNC, places the FT-920 into the Transmit condition.

Pin 4 (Audio Out): Connect this pin to your TNC’s “RX Audio” input line. This is a constant-level (100 mV rms @ 600) audio output line which is not affected by the position of the front-panel AF GAIN control.

Pin 5 (BUSY): This is a “Squelch Status” pin not generally required for digital mode operation. This pin is held at +5V when the squelch is open, and is grounded when the receiver is muted by the squelch (“nosignal” condition).

As viewed from rear panel (not from cable!)

Connector view

Data IN – 100 mVrms / 10k Ohms

Data OUT – 100 mVrms / 600 Ohms

FSK OUT – 25 Vcc/50mA/open colector

Data PTT - 25 Vcc/50mA/open colector

AFSK mode
FT-920 pin 1 Data IN (Audio IN)	SCU-17 pin 1 Data OUT (Audio OUT)
FT-920 pin 2 GND	SCU-17 pin 2 GND
FT-920 pin 3 PTT	SCU-17 pin 3 PTT
FT-920 pin 4 Data OUT (Audio OUT)	SCU-17 pin 5 Data IN (Audio IN)
FT-920 pin 5 Busy	SCU-17 pin 6 SQL IN (Busy)

Menu #	Description	Available choices	AFSK – RTTY	AFSK – WSPR	AFSK – FT4/FT8
U-42	RTTY Generator Tone Pair	Hi 2125U / Lo 1275U / Hi 2125L / Lo 1275L	HI 2125L	HI 2125	HI 2125L
U-43	RTTY Shift	170/425/850 Hz	170	170	170
U-44	Shift Polarity	Normal /Reverse	REV	REV	REV
U-45	Packet Freq. Display Offset	-3.0 ~ + 3.0 kHz	2125	0000	0000
U-46	Packet Subcarrier Frequenc y	1170/1700/2125/2210 USB/LSB	2125U	2125U / 1700U	2125U