Keep a second receiver automatically aligned with your main radio.

CAT4OM can link two radios in the same group with a Leading / Follower relationship.
The Leading radio is the one used by CAT clients, logging software, WSJT-X, or the CAT4OM control page. The Follower radio stays in the background and automatically follows the Leading radio’s frequency and mode.

This is especially useful when you want a listening SDR, panadapter, second receiver, or monitoring radio to stay tuned together with your main transceiver.

How It Works

When the Leading radio changes frequency or mode, CAT4OM waits for the radio to confirm the new state, then mirrors that confirmed state to the Follower.

The change can come from:

• a CAT client connected to CAT4OM;
• the CAT4OM Radio Control page;
• a Hamlib NET rigctl compatible application such as WSJT-X;
• the physical tuning knob on the Leading radio, when the radio reports the change back to CAT4OM.

The Follower tracks the Leading radio’s main VFO, VFO A. It does not follow VFO B, split operation, RIT, XIT, PTT, CW commands, raw CAT commands, or transmit-related actions.

The Follower is designed as a receive-side companion. It is never used as a second transmitter.

Two-Way Frequency Following

Follower links can also be configured as two-way.

When two-way following is enabled, a physical frequency change made on the Follower radio can be sent back to the Leading radio. This lets you tune from either radio while keeping the pair aligned.

Two-way following is intentionally limited and safe:

• only frequency is sent back from the Follower to the Leading;
• mode is never sent back, because the Follower may use a simplified or compatible mode such as USB for a digital mode;
• reverse frequency changes pass through CAT4OM’s normal transmit safety checks;
• if the Leading radio is transmitting, the reverse frequency change is ignored and logged instead of being applied;
• two-way following is off by default and must be enabled per Follower link.

This makes the feature useful for setups where the operator may tune by hand on the receive-side radio, while CAT clients and logs continue to see the Leading radio as the authoritative radio.

Frequency Basis: Dial or Displayed Frequency

CAT4OM supports two ways to decide which frequency the Follower should copy.

For normal radios without transverter offsets, both choices behave the same.

For transverter, IF, or panadapter setups, the choice matters:

• Dial frequency copies the actual frequency used by the Leading radio hardware.
  Use this when the Follower listens to the same IF, panadapter output, or low-frequency signal path.
• Displayed frequency copies the frequency shown to CAT clients after CAT4OM applies offsets.
  Use this when the Follower can directly tune the real on-air frequency.

Example: if a transverter setup makes the radio dial show 20 MHz while CAT4OM displays 10.020 GHz, a panadapter connected to the IF should follow 20 MHz, while an independent microwave receiver should follow 10.020 GHz.

Mode Matching

The Follower also mirrors mode when possible.

If the Follower does not support the exact mode used by the Leading radio, CAT4OM chooses the closest practical receive mode. For example, a digital mode may be mirrored as USB when the Follower does not expose the same digital-mode name.

If no suitable mode is available, CAT4OM keeps the Follower’s mode unchanged and continues mirroring frequency.

Visibility and Control

Follower radios remain visible in CAT4OM configuration and on the web status page, where they are marked as Follower. Two-way links are also marked as Two-way.

Follower radios are hidden from the Control Port and from operating clients. A logging program, WSJT-X, or native CAT4OM control client only sees and controls the Leading radio.

This keeps integrations simple: external software does not need to know that a Follower exists.

Hamlib basic command emulation and WSJT-X

A Leading radio can be exposed through CAT4OM’s Hamlib-like NET rigctl compatible interface.

When an application such as WSJT-X changes the Leading radio through rigctl, the Follower tracks the confirmed Leading radio state automatically.

A Follower radio cannot be exposed directly through the Hamlib-like interface.

Failure Isolation

The Follower can be switched off, disconnected, or temporarily unavailable without affecting the Leading radio.

If the Follower fails to apply a mirrored change, CAT4OM logs the problem and keeps the Leading radio working normally. The Follower resumes tracking when it reconnects and receives fresh state.

A Follower can only start when its configured Leading radio is active.

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