Add fine tune offset for digital voice

routes/dmr.py

@@ -490,6 +490,7 @@ def start_dmr() -> Response:
         device = validate_device_index(data.get('device', 0))
         protocol = str(data.get('protocol', 'auto')).lower()
         ppm = validate_ppm(data.get('ppm', 0))
+        fine_tune = int(data.get('fineTune', 0) or 0)
         demod = str(data.get('demod', 'nfm')).lower()
     except (ValueError, TypeError) as e:
         return jsonify({'status': 'error', 'message': f'Invalid parameter: {e}'}), 400
@@ -500,6 +501,8 @@ def start_dmr() -> Response:
         return jsonify({'status': 'error', 'message': f'Invalid demod. Use: {", ".join(VALID_DEMODS)}'}), 400
     if protocol == 'p25p2' and not is_fme:
         return jsonify({'status': 'error', 'message': 'P25 Phase 2 requires dsd-fme.'}), 400
+    if abs(fine_tune) > 20000:
+        return jsonify({'status': 'error', 'message': 'Fine tune offset too large (max +/- 20000 Hz).'}), 400
 
     # Clear stale queue
     try:
@@ -517,7 +520,7 @@ def start_dmr() -> Response:
 
     dmr_active_device = device
 
-    freq_hz = int(frequency * 1e6)
+    freq_hz = int((frequency * 1e6) + fine_tune)
 
     # Build rtl_fm command (48kHz sample rate for DSD).
     # Squelch disabled (-l 0): rtl_fm's squelch chops the bitstream

static/js/modes/dmr.js

@@ -69,6 +69,7 @@ function startDmr() {
     const protocol = document.getElementById('dmrProtocol')?.value || 'auto';
     const gain = parseInt(document.getElementById('dmrGain')?.value || 40);
     const ppm = parseInt(document.getElementById('dmrPPM')?.value || 0);
+    const fineTune = parseInt(document.getElementById('dmrFineTune')?.value || 0);
     const relaxCrc = document.getElementById('dmrRelaxCrc')?.checked || false;
     const demod = document.getElementById('dmrDemod')?.value || 'nfm';
     const device = typeof getSelectedDevice === 'function' ? getSelectedDevice() : 0;
@@ -84,14 +85,14 @@ function startDmr() {
     // Save settings to localStorage for persistence
     try {
         localStorage.setItem(DMR_SETTINGS_KEY, JSON.stringify({
-            frequency, protocol, gain, ppm, relaxCrc, demod
+            frequency, protocol, gain, ppm, fineTune, relaxCrc, demod
         }));
     } catch (e) { /* localStorage unavailable */ }
 
     fetch('/dmr/start', {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
-        body: JSON.stringify({ frequency, protocol, gain, device, ppm, relaxCrc, demod })
+        body: JSON.stringify({ frequency, protocol, gain, device, ppm, fineTune, relaxCrc, demod })
     })
     .then(r => r.json())
     .then(data => {
@@ -617,12 +618,14 @@ function restoreDmrSettings() {
         const protoEl = document.getElementById('dmrProtocol');
         const gainEl = document.getElementById('dmrGain');
         const ppmEl = document.getElementById('dmrPPM');
+        const fineTuneEl = document.getElementById('dmrFineTune');
         const crcEl = document.getElementById('dmrRelaxCrc');
         const demodEl = document.getElementById('dmrDemod');
         if (freqEl && s.frequency != null) freqEl.value = s.frequency;
         if (protoEl && s.protocol) protoEl.value = s.protocol;
         if (gainEl && s.gain != null) gainEl.value = s.gain;
         if (ppmEl && s.ppm != null) ppmEl.value = s.ppm;
+        if (fineTuneEl && s.fineTune != null) fineTuneEl.value = s.fineTune;
         if (crcEl && s.relaxCrc != null) crcEl.checked = s.relaxCrc;
         if (demodEl && s.demod) demodEl.value = s.demod;
     } catch (e) { /* localStorage unavailable */ }

templates/partials/modes/dmr.html

@@ -51,6 +51,15 @@
                                    title="Frequency error correction for your RTL-SDR dongle. Digital voice is very sensitive to frequency offset.">
                         </div>
 
+                        <div class="form-group">
+                            <label>Fine Tune (Hz)</label>
+                            <input type="number" id="dmrFineTune" value="0" min="-5000" max="5000" step="100" style="width: 100%;"
+                                   title="Offset the tuned frequency by a small amount without changing PPM.">
+                            <span style="font-size: 0.75em; color: var(--text-muted); display: block; margin-top: 2px;">
+                                Adjust in 100 Hz steps; small offsets can dramatically improve P25 decode.
+                            </span>
+                        </div>
+
                         <div class="form-group" style="margin-top: 4px;">
                             <label style="display: flex; align-items: center; gap: 8px; cursor: pointer;">
                                 <input type="checkbox" id="dmrRelaxCrc" style="width: auto; accent-color: var(--accent-cyan);">