diff --git a/src/decoders/trx-cw/src/lib.rs b/src/decoders/trx-cw/src/lib.rs
index aee5063..5f5df35 100644
--- a/src/decoders/trx-cw/src/lib.rs
+++ b/src/decoders/trx-cw/src/lib.rs
@@ -89,12 +89,21 @@ fn goertzel_energy(buf: &[f32], coeff: f32) -> f32 {
 // Tone scan bins
 // ---------------------------------------------------------------------------
 
-const TONE_SCAN_LOW: u32 = 300;
-const TONE_SCAN_HIGH: u32 = 1200;
+const TONE_SCAN_LOW: u32 = 100;
+const TONE_SCAN_HIGH: u32 = 10_000;
 const TONE_SCAN_STEP: u32 = 25;
 const TONE_STABLE_NEEDED: u32 = 3;
 const THRESHOLD: f32 = 0.05;
 
+fn tone_scan_high_for_sample_rate(sample_rate: u32) -> u32 {
+    let nyquist = sample_rate / 2;
+    if nyquist <= TONE_SCAN_LOW + 1 {
+        TONE_SCAN_LOW
+    } else {
+        TONE_SCAN_HIGH.min(nyquist - 1)
+    }
+}
+
 struct ToneScanBin {
     freq: u32,
     coeff: f32,
@@ -152,7 +161,8 @@ impl CwDecoder {
         // Build scan bins
         let mut tone_scan_bins = Vec::new();
         let mut f = TONE_SCAN_LOW;
-        while f <= TONE_SCAN_HIGH {
+        let scan_high = tone_scan_high_for_sample_rate(sample_rate);
+        while f <= scan_high {
             let bk = (f as f32 * window_size as f32 / sample_rate as f32).round();
             let b_omega = (2.0 * std::f32::consts::PI * bk) / window_size as f32;
             tone_scan_bins.push(ToneScanBin {
@@ -195,7 +205,10 @@ impl CwDecoder {
     }
 
     pub fn set_tone_hz(&mut self, tone_hz: u32) {
-        let tone_hz = tone_hz.clamp(TONE_SCAN_LOW, TONE_SCAN_HIGH);
+        let tone_hz = tone_hz.clamp(
+            TONE_SCAN_LOW,
+            tone_scan_high_for_sample_rate(self.sample_rate),
+        );
         self.recompute_goertzel(tone_hz);
     }