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Radio Control

The Radio Control tab is where you connect a rig (and rotator), pick a transponder, and let FBSAT59 keep the frequency Doppler-corrected during a pass. Connecting the hardware is covered in Setup — Step 2; this page explains the tab itself.

What Hamlib gives you

Hamlib is compiled into FBSAT59, so it can drive 700+ rig models with no external rigctld. Two connection modes are chosen per rig under Radio → Rig Settings…:

  • Direct (Hamlib built-in) — FBSAT59 talks to the rig over its USB/serial CAT cable.
  • NET (rigctld compatible) — FBSAT59 connects over TCP to a running rigctld (on this or another machine), so other software can share the rig.

Radios verified on real hardware so far: Yaesu FTX-1F and FT-991/FT-991A/ FT-991AM; Icom IC-9100, IC-9700 and IC-705. Anything else Hamlib supports should work — if your exact model isn't listed in Rig Settings, a close one usually does (e.g. "FT-991" for an FT-991A).

Connecting

  1. Configure the rig on the Rig 1 tab of Radio → Rig Settings… (see Setup — Step 2).
  2. On the Radio Control tab, click Connect Rig 1. The Status box shows the rig state and the window status bar shows RIG: 1. The button becomes Disconnect Rig 1, or Retry if the connection failed.

The rotator connects the same way with Connect Rotator (Setup — Step 4).

The tab, section by section

Satellite

  • Offset (Hz) — a manual frequency nudge added on top of the Doppler correction, for a rig that reads a little off.
  • T — Tune: reset downlink/uplink to the centre of the transmitter's band.
  • L — Lock: a toggle (also Ctrl+L). See Lock below.
  • Transmitter — the SatNOGS transponders for the selected satellite. Picking one sets the downlink, uplink and mode.

Frequency

  • Downlink / Uplink — the current tuned frequencies. During a pass the downlink (and uplink) update about once a second as Doppler is applied.
  • Mode — set from the transponder. For SSB transponders a small CW button appears that toggles CW on both VFOs; a data-mode button toggles a data variant.
  • CTCSS — a send-tone button, plus a 74.4 Hz (Activation) button for SO-50's 10-minute timer.

Rotator — live AZ/EL readout, and a Manual AZ/EL entry with Go / Stop / Park / Resume Tracking for pointing the antenna without tracking.

Status — Rig 1 / Rig 2 / Rotator connect buttons and state, the South Init checkbox (why), and Cycle (ms) — the rig CAT / Doppler update interval. Raise it if an older rig can't keep up with per-second retunes.

Autotrack and Recording round out the tab.

Doppler correction

As a satellite moves relative to you its signal shifts in frequency. With a transponder selected and a rig connected, FBSAT59 recomputes the shift every Cycle milliseconds and retunes the rig so the received frequency stays put:

  • Around AOS the satellite is approaching — the downlink sits above its nominal frequency.
  • At TCA (closest approach, peak elevation) the shift is near zero.
  • Toward LOS the satellite is receding — the downlink drops below nominal.

Lock

The L button (or Ctrl+L from any tab) is an on/off toggle — it turns yellow when on. Its main job is letting you work anywhere inside a linear transponder's passband.

Lock off — the default. FBSAT59 owns the downlink: every cycle it writes the Doppler-corrected downlink frequency to the rig, holding you on the transponder's centre.

That is fine for an FM bird (one channel), but a linear (SSB/CW) transponder passes a whole slice of band and you almost never want the centre — you want your spot in the passband: a specific station to work, or a clear frequency to call on. The moment you turn the VFO to get there, Lock-off drags you straight back on the next cycle.

Lock on — you own the downlink. FBSAT59 stops writing the downlink to the rig, so you can tune freely to any frequency inside the passband. It keeps reading where you've set the dial and moves the uplink to match — correctly mirrored for an inverting transponder — so your transmitted signal comes out where you are listening, and it keeps applying Doppler correction from that point for the rest of the pass. Each manual retune registers on the next Doppler cycle, so give it a second.

Turning Lock off again resumes automatic correction from wherever you left the dial, not from the transponder centre. It only snaps back to the centre when you switch transponder or press T.

(The same mechanism also lets you correct by ear if a beacon's real frequency has drifted from the database value.)

Frequency preset before connecting

For rigs that support it, selecting a transponder writes the starting frequencies to the radio immediately — even before you press Connect Rig 1 — so the rig already shows the right pass frequencies.

Dual radio (Rig 1 + Rig 2)

Enable Rig 2 on its tab in Rig Settings… to run two radios at once — for example downlink on Rig 1 and uplink on Rig 2 for full-duplex work. Either slot can instead be an SDR (Setup — Step 3). Full steps: Setup — Dual Radio Setup.

Troubleshooting

Symptom Try
"Serial port not found" / won't connect Check the cable; install the rig's USB driver; on Linux confirm the port with lsusb / ls /dev/ttyUSB*; match the baud rate to the rig's CAT setting (the Test button in Rig Settings checks it)
Your exact model isn't in the list Search in the Rig Model box; try a closely related model
Frequency doesn't change on picking a transponder Confirm the status bar shows RIG: 1; check the rig is on the expected VFO/mode
Doppler seems too large or too small Update the TLE (Satellite → Update TLE) and re-check your QTH — stale elements or a wrong location skew the shift
Frequency jitter on an older rig Increase Cycle (ms) on the Radio Control tab

More in Troubleshooting.

Next steps