Elecraft K4, K3S, KX2 & KX3

Elecraft rigs speak a Kenwood-derived protocol, but each model has its own quirks — and picking the exact Radio Model in POTACAT’s rig settings is what makes them behave.

K4 / K4D

Pick the K4 model

Select K4 explicitly as the Radio Model. The K4 uses Elecraft’s DT data sub-mode commands rather than the Kenwood ones: for FT8/DIGU POTACAT sends MD6 (DATA) + DT0 (DATA-A), and MD9 (DATA-REV) for DIGL. With a generic profile the radio lands in the wrong data variant, so the model selection matters.

Network CAT and remote operation

• For remote control over the network, use the K4 Remote (network) connection type (distinct from the generic IP Radio (TCP CAT)): enter the K4’s IP or hostname, port 9205 (plain TCP), and the remote password you set on the radio.
• Port 9204 (TLS-PSK) is not supported — use 9205.
• POTACAT performs the K4’s authenticated handshake and keeps the session alive with a heartbeat. A wrong password shows up in the log as socket closed before session established.

SWR bar stays empty

The K4 rejects the K3-era RM1; SWR query, so POTACAT doesn’t poll SWR on the K4. An empty SWR bar is normal on this radio.

Tip: If the bandwidth looks wide after clicking a spot, check the K4’s own per-mode bandwidth defaults — that’s usually the radio’s stored setting, not POTACAT.

K3 / K3S

If CW spot clicks land you in a wide filter, two rig-side settings are responsible:

1. CONFIG > RX BW LOCK must be OFF. When bandwidth is locked, the K3 silently ignores the FW (filter width) commands POTACAT sends.
2. The per-mode filter bank (the FB button) must have a narrow roofing filter (250/500 Hz) selected for CW. POTACAT sends only FW — the DSP width — and never FB; the roofing filter choice is something you set once on the rig, and FW can only narrow within it.

Tip: Set your preferred per-mode filter widths in Settings > Tuning and they’ll persist across spot clicks and band changes.

KX2 / KX3

• Both work out of the box over Serial CAT (Kenwood) at 38400 baud.
• FT8/JTCAT: the KX-series per-band memory recall can override DATA A when you change bands. Set the Radio Model to KX2/KX3 so POTACAT re-sends the mode after each QSY.
• The K3 filter-width advice above applies here too: set per-mode widths in Settings > Tuning.