diff --git a/static/css/components/signal-cards.css b/static/css/components/signal-cards.css
index 4fbe665..283aeb6 100644
--- a/static/css/components/signal-cards.css
+++ b/static/css/components/signal-cards.css
@@ -1158,6 +1158,13 @@
     border: none;
 }
 
+.signal-strength-indicator.no-data {
+    font-family: 'JetBrains Mono', monospace;
+    font-size: 9px;
+    color: var(--text-dim);
+    opacity: 0.5;
+}
+
 .signal-strength-bars {
     display: inline-block;
     vertical-align: middle;
diff --git a/static/js/components/signal-cards.js b/static/js/components/signal-cards.js
index 04ff5e9..de7f18c 100644
--- a/static/js/components/signal-cards.js
+++ b/static/js/components/signal-cards.js
@@ -827,9 +827,11 @@ const SignalCards = (function() {
         const stats = getAddressStats('sensor', msg.id);
         const seenCount = stats ? stats.count : 1;
 
-        // Get signal strength if available
-        const rssi = msg.rssi || msg.signal_strength || msg.snr || null;
-        const signalIndicator = createSignalIndicator(rssi, { compact: true });
+        // Get signal strength if available (rtl_433 uses 'snr' for signal-to-noise ratio)
+        const rssi = msg.rssi || msg.signal_strength || msg.snr || msg.noise || null;
+        const signalIndicator = rssi !== null
+            ? createSignalIndicator(rssi, { compact: true })
+            : '<span class="signal-strength-indicator compact no-data" title="No signal data available">--</span>';
 
         // Determine sensor type icon
         let sensorIcon = '📡';