From d347b493d9c5e94639b67bc05183a66a4411b5da Mon Sep 17 00:00:00 2001
From: Stan Grams <sjg@haxx.space>
Date: Sat, 1 Aug 2026 02:02:13 +0200
Subject: [PATCH] [fix](trx-frontend): make auto bandwidth modulation-aware

---
 .../trx-frontend-http/assets/web/app.js       | 95 ++++++++++++-------
 1 file changed, 62 insertions(+), 33 deletions(-)

diff --git a/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js b/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js
index b2909005..cc32a055 100644
--- a/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js
+++ b/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js
@@ -4348,64 +4348,93 @@ async function applyBandwidthFromInput() {
   } catch (_) {}
 }
 
-function estimateBandwidthAroundPeak(data, centerHz) {
+function estimateOccupiedBandwidth(data, centerHz) {
   if (!data || !isBinsArray(data.bins) || data.bins.length < 3 || !Number.isFinite(centerHz)) {
     return null;
   }
 
   const bins = data.bins;
   const maxIdx = bins.length - 1;
+  const hzPerBin = data.sample_rate / maxIdx;
   const fullLoHz = data.center_hz - data.sample_rate / 2;
   const centerIdx = Math.max(
     1,
     Math.min(maxIdx - 1, Math.round(((centerHz - fullLoHz) / data.sample_rate) * maxIdx)),
   );
-  const searchRadius = Math.max(6, Math.min(120, Math.round(maxIdx * 0.03)));
-  const searchLo = Math.max(1, centerIdx - searchRadius);
-  const searchHi = Math.min(maxIdx - 1, centerIdx + searchRadius);
-
-  let peakIdx = centerIdx;
-  for (let i = searchLo; i <= searchHi; i++) {
-    if (bins[i] > bins[peakIdx]) peakIdx = i;
-  }
+  const mode = (modeEl ? modeEl.value : "USB").toUpperCase();
+  const [defaultBw, minBw, maxBw, stepBw] = mwDefaultsForMode(mode);
+  const oneSided = mode === "USB" || mode === "DIG" || mode === "CW"
+    ? 1
+    : mode === "LSB" || mode === "CWR" ? -1 : 0;
+  const isWfm = mode === "WFM";
 
+  // Reduce single-bin peaks and holes before finding occupied-channel edges.
+  // WFM needs a wider smoothing window because its energy is noise-like and
+  // spread across the entire channel rather than concentrated at a carrier.
+  const smoothRadius = isWfm ? 3 : 1;
+  const smoothed = bins.map((_, i) => {
+    let sum = 0;
+    let count = 0;
+    for (let j = Math.max(0, i - smoothRadius); j <= Math.min(maxIdx, i + smoothRadius); j++) {
+      sum += bins[j];
+      count += 1;
+    }
+    return sum / count;
+  });
   const sorted = [...bins].sort((a, b) => a - b);
   const noise = sorted[Math.floor(sorted.length * 0.2)];
-  const peak = bins[peakIdx];
-  const threshold = Math.max(noise + 4, peak - Math.max(8, (peak - noise) * 0.35));
+  const maxSpanBins = Math.max(2, Math.ceil(maxBw / hzPerBin));
+  const searchHalfBins = oneSided === 0 ? Math.ceil(maxSpanBins / 2) : maxSpanBins;
+  const searchLo = Math.max(1, centerIdx - (oneSided > 0 ? 2 : searchHalfBins));
+  const searchHi = Math.min(maxIdx - 1, centerIdx + (oneSided < 0 ? 2 : searchHalfBins));
+  let peak = -Infinity;
+  for (let i = searchLo; i <= searchHi; i++) peak = Math.max(peak, smoothed[i]);
+  const snr = peak - noise;
+  if (!Number.isFinite(snr) || snr < (isWfm ? 5 : 4)) return defaultBw;
 
-  let left = peakIdx;
-  let right = peakIdx;
-  let belowCount = 0;
-  for (let i = peakIdx; i > 1; i--) {
-    if (bins[i] < threshold) belowCount += 1;
-    else belowCount = 0;
-    if (belowCount >= 2) break;
-    left = i;
+  // A threshold relative to the noise floor finds occupied bandwidth much
+  // more reliably than one relative to the peak.  The latter fails for WFM,
+  // whose multiplex spectrum has peaks, notches, and no narrow centre carrier.
+  const threshold = noise + Math.max(3, Math.min(isWfm ? 6 : 10, snr * (isWfm ? 0.18 : 0.28)));
+  const allowedGap = Math.max(isWfm ? 4 : 2, Math.ceil((isWfm ? 12_000 : stepBw) / hzPerBin));
+
+  function occupiedExtent(direction, limitBins) {
+    let lastOccupied = centerIdx;
+    let gap = 0;
+    for (let n = 0; n <= limitBins; n++) {
+      const i = centerIdx + direction * n;
+      if (i <= 0 || i >= maxIdx) break;
+      if (smoothed[i] >= threshold) {
+        lastOccupied = i;
+        gap = 0;
+      } else if (++gap > allowedGap) {
+        break;
+      }
+    }
+    return Math.abs(lastOccupied - centerIdx) * hzPerBin;
   }
 
-  belowCount = 0;
-  for (let i = peakIdx; i < maxIdx - 1; i++) {
-    if (bins[i] < threshold) belowCount += 1;
-    else belowCount = 0;
-    if (belowCount >= 2) break;
-    right = i;
+  let rawBw;
+  if (oneSided !== 0) {
+    rawBw = occupiedExtent(oneSided, maxSpanBins);
+  } else {
+    const leftHz = occupiedExtent(-1, searchHalfBins);
+    const rightHz = occupiedExtent(1, searchHalfBins);
+    // A symmetric RF filter must contain the larger of the two sidebands.
+    rawBw = 2 * Math.max(leftHz, rightHz);
   }
 
-  const shoulderPad = Math.max(1, Math.round((right - left) * 0.08));
-  left = Math.max(0, left - shoulderPad);
-  right = Math.min(maxIdx, right + shoulderPad);
-
-  const hzPerBin = data.sample_rate / maxIdx;
-  const rawBw = Math.max(hzPerBin, (right - left) * hzPerBin);
-  const [, minBw, maxBw, stepBw] = mwDefaultsForMode(modeEl ? modeEl.value : "USB");
+  // Add a transition-band margin. Reject implausibly narrow WFM measurements:
+  // they are normally a pilot/centre feature or a neighbouring narrow signal.
+  rawBw *= isWfm ? 1.08 : 1.12;
+  if (isWfm && rawBw < defaultBw * 0.55) return defaultBw;
   const clamped = Math.max(minBw, Math.min(maxBw, rawBw));
   return Math.max(stepBw, Math.round(clamped / stepBw) * stepBw);
 }
 
 async function applyAutoBandwidth() {
   if (!lastSpectrumData || lastFreqHz == null) return;
-  const estimated = estimateBandwidthAroundPeak(lastSpectrumData, lastFreqHz);
+  const estimated = estimateOccupiedBandwidth(lastSpectrumData, lastFreqHz);
   if (!Number.isFinite(estimated) || estimated <= 0) {
     syncBandwidthInput(currentBandwidthHz);
     return;