Radio and rotator

OscarWatch can steer your beam and keep your radio on frequency during a pass. You do not need to understand every setting on day one — pick your radio below and read that page first.

Before you plug in

• Use a USB serial lead (or proper interface) to the radio and rotator.
• Prefer a genuine FTDI USB–serial adapter (or the radio’s own USB port). Cheap Prolific clones are a common cause of missed CAT and flaky reconnects — see USB serial adapters.
• Radio and rotator need different serial ports — and a third port if you use GPS. On Linux, use a stable by-id or udev path so numbers do not swap after reboot — see Linux serial ports.
• Close other programs that might hold the port (HRD, WSJT-X rig control, Hamlib, etc.).
• For normal cross-band satellites, your radio should be in satellite mode when tracking starts (OscarWatch usually sets this), except the Kenwood TS-2000 — you must select SAT yourself first.
• For receive-only modes (ISS SSTV, beacons — uplink 0 in the database), you do not need satellite mode; OscarWatch tunes the downlink only.

Which radio do you have?

Your rig	Read this
ICOM IC-910, IC-9700, IC-9100, IC-821H	ICOM radios — one radio, Main/Sub satellite layout
ICOM IC-705, IC-7300, IC-905, IC-7100, or IC-706 series as a second radio	ICOM dual radio (paired with another rig)
Yaesu FT-847	Yaesu radios — classic satellite CAT radio
FlexRadio (SmartSDR API)	FlexRadio — full duplex via LAN API to the radio
Yaesu FT-817, FT-818, FT-857, FT-991, FTX-1 as downlink or uplink leg	Yaesu dual radio
Kenwood TS-2000	Kenwood TS-2000 (manual steps before tracking)
Kenwood TH-D74, TH-D75 as downlink or uplink leg	Kenwood dual radio
No hardware yet	Dummy rig in Settings — test the map and frequencies only

Everything is configured under Settings → Radio: rig type, serial port (COM port on Windows, device path on Linux/macOS), and (for ICOM) CI-V address. Use Pause CAT if you want to tune by hand without OscarWatch fighting the dial.

One radio or two?

Single radio — one physical rig handles both receive and transmit (ICOM satellite rigs, FT-847, TS-2000). OscarWatch uses satellite mode or split as your rig requires.

Dual radio — downlink on one radio, uplink on another (common: FT-818 for RX + IC-706 for TX). Enable Settings → Radio → Dual radio and set a COM port for each leg, or use an SDR downlink (rigctl TCP) with SDR++ or SDR Connect for receive. See Yaesu dual, ICOM dual, or SDR dual for wiring and ports.

What happens during a pass

When you track a satellite and CAT is enabled, OscarWatch:

• Sets the right modes and satellite layout at pass start (rig-dependent).
• Updates receive and transmit frequencies as Doppler changes.
• Applies your RX and TX offsets from the frequency panel.
• Sends CTCSS when your radio and satellite mode support it.
• Steers the rotator (if configured) while the satellite is above your track-start elevation.

Standby in the sidebar parks the rotator and pauses CAT. Use it while browsing the map. The heading changes to Standby until you press Resume tracking.

Tuning — offsets and Doppler

Two ideas that confuse newcomers:

Topic	Plain English	Read more
RX / TX offsets	Nudge listen and transmit frequencies to find a clear spot in the passband — stored per satellite.	When to use offsets · Frequency panel
Doppler tuning	How often OscarWatch updates the radio, and optional extras (lead, adaptive) for sharp passes.	Doppler tuning guide
Passband trim	On linear SSB, spin the receive dial to hunt the signal; OscarWatch learns your offset.	Spinning the dial

Receive-only modes (SSTV, beacons)

When uplink is 0 in the database (e.g. ISS SSTV), the frequency panel shows uplink as a dash. OscarWatch only corrects the downlink.

• ICOM IC-910 / IC-9700 / IC-9100 / IC-821H — turns satellite mode off, puts the downlink band on Main, applies Doppler there only.
• Kenwood TS-2000 — keeps SATL and Doppler-tracks the downlink on FA only (see Kenwood help).
• Other rigs — receive frequency only; layout depends on the driver.

After a voice satellite pass, switching to ISS SSTV is enough — OscarWatch reconfigures at the next track start.

Linear CW note

On linear SSB transponders, the Voice / CW buttons in the frequency panel choose how CAT sets modes. With Linear CW: keep receive in USB/LSB checked in Settings (usual), transmit goes to CW and receive stays in sideband. See Frequencies and Shortcuts (Ctrl+W).

Rotators

If you use a computer-controlled rotator, OscarWatch can point your antenna during a pass while the satellite is above your track-start elevation. You need a separate COM port from the radio.

Topic	Plain English	Read more
Setup	Pick your controller type (GS-232, SPID, SPID MD-01 TCP, EasyComm II, SAEBRTrack, or OZ9AAR URC TCP), then a COM port or TCP host/port (including TCP serial / ser2net for serial protocols), park position, and az/el limits.	Rotator setup
Park & Standby	Beam goes to park when a pass ends or you press Standby; Resume tracking starts tracking again.	Park and tracking
Manual pointing	In Standby, menu Rotator… lets you aim the beam for a quick contact without resuming pass tracking.	Manual rotator
Keyhole avoidance	Optional for over-the-top mounts (0–180° elevation) on very high passes where the rotator can struggle near zenith.	Keyhole avoidance

Configure under Settings → Rotator.