diff --git a/telemetry.go b/telemetry.go
index beca88f..77d9975 100644
--- a/telemetry.go
+++ b/telemetry.go
@@ -85,15 +85,27 @@ func (a *App) sendTelemetryHeartbeat() {
 		return // already counted today
 	}
 
+	// distinct_id identifies the USER. Prefer the station callsign — it's stable
+	// across every machine/reinstall the same operator runs, so one op counts as
+	// one user (a callsign is public in amateur radio). The random per-install ID
+	// is only a fallback until a callsign is configured; without it the same op on
+	// a laptop + desktop + Maestro showed up as three "users". install_id rides
+	// along as a property so multiple machines under one callsign stay visible.
+	installID := a.telemetryInstallID()
+	distinctID := installID
+	if call := a.activeCallsign(); call != "" {
+		distinctID = call
+	}
 	payload := map[string]any{
 		"api_key":     posthogAPIKey,
 		"event":       "app_opened",
-		"distinct_id": a.telemetryInstallID(),
+		"distinct_id": distinctID,
 		"properties": map[string]any{
-			"version": appVersion,
-			"os":      runtime.GOOS,
-			"arch":    runtime.GOARCH,
-			"$lib":    "opslog",
+			"version":    appVersion,
+			"os":         runtime.GOOS,
+			"arch":       runtime.GOARCH,
+			"install_id": installID,
+			"$lib":       "opslog",
 		},
 		"timestamp": time.Now().UTC().Format(time.RFC3339),
 	}