[Elecraft] Elecraft KAT500 Display Unit with wifi

[Keith Ennis]

KAT500 Antenna Tuner Remote Display & Web Monitor

This project provides a standalone remote display and web interface for the Elecraft KAT500 automatic antenna tuner, built around a Seeed Studio XIAO microcontroller.

Graphic Display Unit 4x4x2 inches in size.

A 256×64 NHD SSD1322 display provides a real-time readout of KAT500 operating data, organized into three columns. The left column shows the current operating mode (BYPASS / MANUAL / AUTO), selected antenna (1–3), and active band. The center column displays SWR after and before tuning. The right column shows the L/C network values in µH and pF, with component order automatically flipped based on whether the network is configured for the transmitter or antenna side. A small WiFi status indicator in the top-right corner shows connection state at a glance.

On power-up a startup splash is displayed, followed by the connection information screen showing the assigned IP address and mDNS hostname once WiFi connects. If a fault condition is detected, the normal display is immediately replaced by a full-screen inverted overlay with bold centered text identifying the fault. The overlay flashes every 5 seconds — briefly blanking then reappearing — until the KAT500 reports the fault cleared.

Web Interface

Accessible at kat500.local or any network connected device using free Sailscale.The device IP address from any browser on the same network. The web interface presents all KAT500 data in a phosphor-green monochrome monitor style. An 8-cell grid displays Mode, Antenna, Band, Side, SWR After, SWR Before, Inductance, and Capacitance, with SWR values color-coded green, amber, or red based on threshold. A pulsing red fault banner appears above the grid whenever a fault condition is active, displaying the full fault description.

A fault condition may be cleared by tapping the TUNE button or turning the KAT500 off and back on. Fault code 4 is cleared by a transmission with low SWR.

A controls row provides four buttons: a Power toggle (with confirmation prompt before turning off, plus verified readback), a Mode selector (BYPASS / MANUAL / AUTO), an Antenna selector (ANT 1 / ANT 2 / ANT 3), and a Full Tune button that initiates a tuning cycle and reports success or failure. A footer shows the active antenna number, WiFi connection status, and a running uptime timer.

WiFi credentials are entered once through a captive portal on first use and saved automatically for all subsequent power cycles. OTA firmware updates are available at Kat500.local/update.

Keith, KV5J

http://www.kv5j.com/store

DDUinfo at yahoo.com