I'm not quite sure why things worked in today's testing, possibly I was just in a dead zone yesterday. Here's the setup that's working though:
DRA-50 is plugged into radio's "Data" port (on main body) and into laptop. This is the port for using an external TNC, which is indicated by a plain 'D' next to the power level indicator on whichever band it's set to. (The internal TNC's band is indicated by a black square with a light 'D' in it.) Tuning must be done manually.
Note: I renamed the input and output devices of the DRA-50 for easy identification. By default they show up as "USB PnP Sound Device". After connecting the first time, Windows may make both sides the default audio input/output devices. You do not want this. Make sure to change the default devices back to the built-in speakers and microphone or whatever else you want to use.
Sound control panel, DRA-50
- Speaker Level: 100
- Microphone Level: 50
- AGC: off (unchecked)
- Disable all enhancements
- Allow applications to take exclusive control of this device: checked
- Give exclusive mode applications priority: checked
- Spatial sound format: Off
Vara FM configuration:
Settings -> VARA Setup...
- Command: 8300
- Data: 8301
- FM System: Narrow
- Retries: 2
- callsign and registration key also filled in
Settings -> SoundCard...
- Device Input: DRA-50
- Device Output: DRA-50
- PTT: RA-Board
- Drive level: -5 dB
Settings -> PTT...
Kenwood D-710G settings:
- internal TNC off
- set band to be used by external TNC in menu
918 (AUX -> EXT. DATA BAND)
- manually tune to desired winlink frequency
- adjust squelch just high enough to ignore background static
- power level medium -- I've heard running data modes on high may be too much duty cycle for the radio, and also distort your outgoing signal.
919 (AUX -> EXT. DATA SPEED): 1200 bps