diff --git a/changelog.json b/changelog.json
index 4f7d571..52b05f1 100644
--- a/changelog.json
+++ b/changelog.json
@@ -1,4 +1,14 @@
 [
+  {
+    "version": "0.27.3",
+    "date": "",
+    "en": [
+      "KPA500: the amplifier no longer switches itself off and commands respond instantly. A command this model does not know (the KPA1500’s ATU poll) was tearing the link down every cycle, and each reconnect toggled the serial control lines — which are the KPA500’s power switch. The lines are now held steady, silence is not treated as a dead link, and the baud is picked from a list."
+    ],
+    "fr": [
+      "KPA500 : l’ampli ne s’éteint plus tout seul et les commandes répondent instantanément. Une commande inconnue de ce modèle (le poll ATU du KPA1500) détruisait le lien à chaque cycle, et chaque reconnexion basculait les lignes de contrôle série — qui sont l’interrupteur du KPA500. Les lignes sont désormais tenues stables, le silence n’est plus traité comme un lien mort, et le baud se choisit dans une liste."
+    ]
+  },
   {
     "version": "0.27.2",
     "date": "",
diff --git a/frontend/src/components/SettingsModal.tsx b/frontend/src/components/SettingsModal.tsx
index 6633eb0..ec137dc 100644
--- a/frontend/src/components/SettingsModal.tsx
+++ b/frontend/src/components/SettingsModal.tsx
@@ -4416,8 +4416,17 @@ function SettingsModalImpl({ onClose, onSaved, initialSection, onMainPaneChanged
                     </div>
                     <div className="space-y-1">
                       <Label>Baud</Label>
-                      <Input type="number" min={1200} value={amp.baud}
-                        onChange={(e) => patchAmp(i, { baud: parseInt(e.target.value) || 115200 })} className="font-mono" />
+                      {/* A list, not a free number: the KPA500 report that
+                          began this had its operator wondering whether a typed
+                          baud was the whole problem. These are the rates the
+                          supported amplifiers actually speak. */}
+                      <select value={String(amp.baud)}
+                        onChange={(e) => patchAmp(i, { baud: parseInt(e.target.value) })}
+                        className="h-9 w-full px-2 rounded-md border border-border bg-background text-sm font-mono">
+                        {[4800, 9600, 19200, 38400, 57600, 115200].map((b) => (
+                          <option key={b} value={String(b)}>{b}</option>
+                        ))}
+                      </select>
                     </div>
                   </div>
                 ) : (
diff --git a/internal/kpa/kpa.go b/internal/kpa/kpa.go
index 788503f..2651549 100644
--- a/internal/kpa/kpa.go
+++ b/internal/kpa/kpa.go
@@ -79,9 +79,10 @@ type Config struct {
 type Client struct {
 	cfg Config
 
-	mu   sync.Mutex // serialises the connection: one question at a time
-	conn io.ReadWriteCloser
-	rd   *bufio.Reader
+	mu     sync.Mutex // serialises the connection: one question at a time
+	conn   io.ReadWriteCloser
+	rd     *bufio.Reader
+	skipTP bool // ^TP went unanswered once — a KPA500, no ATU; never ask again
 
 	statusMu sync.RWMutex
 	status   Status
@@ -183,6 +184,13 @@ func (c *Client) connectLocked() error {
 		if err != nil {
 			return fmt.Errorf("cannot open %s: %w", c.cfg.ComPort, err)
 		}
+		// The KPA500 is POWER-CONTROLLED by these lines: the Elecraft utility
+		// switches the amplifier on by raising them. Held asserted, once, and
+		// never touched again — reconnect cycles that toggled them were
+		// switching a KPA500 OFF twenty seconds after its operator pressed
+		// nothing but Standby.
+		_ = p.SetDTR(true)
+		_ = p.SetRTS(true)
 		_ = p.SetReadTimeout(ioTimeout)
 		c.conn = p
 	}
@@ -214,7 +222,13 @@ func (c *Client) ask(cmd string) (string, error) {
 	// the frame.
 	line, err := c.rd.ReadString(';')
 	if err != nil {
-		c.dropLocked()
+		// NOT dropped. A command this model simply does not know (^TP is the
+		// KPA1500's ATU — a KPA500 never answers it) is silence, not a dead
+		// link, and dropping here tore the connection down on every slow poll
+		// cycle: two seconds of stalled commands, a reconnect, and a DTR
+		// toggle the amplifier read as the off switch. Nothing arrived, so
+		// nothing is left to desynchronise the next exchange. Write errors —
+		// the genuinely dead link — still drop, above.
 		return "", fmt.Errorf("no answer to %s: %w", cmd, err)
 	}
 	return strings.TrimSpace(line), nil
@@ -364,12 +378,21 @@ func (c *Client) pollOnce(n uint64) {
 			c.statusMu.Unlock()
 		}
 	}
+	if c.skipTP {
+		return
+	}
 	if reply, err := c.ask("^TP;"); err == nil {
 		if v, err := parseInt(reply, "^TP"); err == nil {
 			c.statusMu.Lock()
 			c.status.Tuning = v == 1
 			c.statusMu.Unlock()
 		}
+	} else {
+		// One silence is the model's answer for good: a KPA500 has no ATU and
+		// will never answer ^TP — asking again every cycle cost a two-second
+		// stall each time.
+		c.skipTP = true
+		applog.Printf("kpa: ^TP unanswered — no ATU on this model, not asking again")
 	}
 }