I've been running RTTY AFSK successfully with my IC-7300 using Ham Radio Deluxe/DM780, but I can't get FSK working properly. When I switch to RTTY FSK mode, I get solid carrier but no FSK modulation - just a continuous tone. I'm using both USB and CI-V cables as recommended online, with USB on COM3 and FTDI on COM4. The rig switches to TX but there's no warble or shift.

Has anyone successfully configured FSK with the 7300? I'm wondering if there's a menu setting I'm missing or if this is a common DM780 timing issue. PSK31 AFSK works perfectly on the same setup.

I had the exact same problem with my 7300 and DM780. It's definitely a software timing issue - FSK requires precise PTT and keying coordination that DM780 sometimes struggles with. Try switching to MMTTY engine instead, or consider Fldigi which handles FSK much more reliably on the 7300.

Check your CI-V settings in the radio - make sure CI-V Transceive is ON and baud rate matches DM780 (usually 19200). Also verify the FSK keying is set to RTTY-R in the RTTY menu. The 7300 can be finicky about FSK timing with some software.

Why not just stick with AFSK? Honestly, with modern rigs like the 7300, the difference in performance between FSK and AFSK is negligible. AFSK is much easier to set up and you're already working fine with it for contests.