SDR downlink (dual radio)

In Settings → Radio → Dual radio, set the downlink to SDR (rigctl TCP) and configure your uplink radio as usual (serial CAT). OscarWatch connects to the SDR application’s rigctl server over TCP: it pushes Doppler-corrected RX frequency and reads the waterfall VFO for interactive passband trim.

RX-only operation

To use the SDR as a receive-only device with no transmit radio, set the uplink to Dummy uplink (RX only). OscarWatch will track the satellite and display the computed uplink frequency, but it will not send CAT commands to a transmit radio.

SDR++

1. Open Module Manager and add rigctl_server if it is not already present.
2. Enable the server and note the TCP port (often 4532).
3. In OscarWatch downlink settings: host 127.0.0.1, matching port, then Test rigctl connection.
4. Use the SDR++ preset (4532) button if that matches your server port.

SDR Connect

1. Enable the rigctl server in SDR Connect (fixed port 5454).
2. In OscarWatch, use the SDR Connect preset (5454) button and test the connection.

Operating notes

• Linear passes: tune on the SDR waterfall — OscarWatch reads frequency via rigctl and applies NOR/REV passband trim so the TX radio follows your RX hunt while uplink Doppler continues. See spinning the dial.
• FM passes: Doppler updates are pushed to the SDR centre frequency; spin the TX radio or overlay for uplink offset as usual.
• Use 100 ms or more downlink CAT delay when the SDR feels sluggish.
• SDR is downlink only; the uplink can be a supported CAT radio or Dummy uplink (RX only) for receive-only operation.

Troubleshooting

• Test rigctl connection fails — server not started, wrong port, or firewall blocking localhost TCP.
• No RX Doppler — confirm dual radio is complete, not in Standby, and CAT pause is off. See Problems?.
• Waterfall clicks do not move passband — rigctl server must answer f (get frequency); check SDR++ build and server module.