fix(weather-sat): lower default gain to 30 dB to prevent ADC saturation

Strong passes at 40 dB (the previous default) cause RTL-SDR ADC clipping, producing a distorted IQ stream that SatDump cannot lock onto. 30 dB is a safer starting point that still captures weak passes cleanly. Also adds a UI hint below the gain control explaining the saturation issue. Closes #185
2026-04-23 22:30:00 -07:00 · 2026-04-05 14:20:06 +01:00
parent 6572119360
commit 6ea34a4c60
3 changed files with 215 additions and 214 deletions
--- a/templates/partials/modes/weather-satellite.html
+++ b/templates/partials/modes/weather-satellite.html
@@ -2,13 +2,13 @@
 <div id="weatherSatMode" class="mode-content">
    <div class="section">
        <h3>Weather Satellite Decoder</h3>
-        <div class="alpha-mode-notice">
-            ALPHA: Weather Satellite capture is experimental and may fail depending on SatDump version, SDR driver support, and pass conditions.
-        </div>
-        <p class="info-text" style="font-size: 11px; color: var(--text-dim); margin-bottom: 12px;">
-            Receive and decode Meteor LRPT weather imagery.
-            Uses SatDump for live SDR capture and image processing, and also shows Meteor imagery produced by the ground-station scheduler.
-        </p>
+        <div class="alpha-mode-notice">
+            ALPHA: Weather Satellite capture is experimental and may fail depending on SatDump version, SDR driver support, and pass conditions.
+        </div>
+        <p class="info-text" style="font-size: 11px; color: var(--text-dim); margin-bottom: 12px;">
+            Receive and decode Meteor LRPT weather imagery.
+            Uses SatDump for live SDR capture and image processing, and also shows Meteor imagery produced by the ground-station scheduler.
+        </p>
    </div>

    <div class="section">
@@ -18,11 +18,12 @@
            <select id="weatherSatSelect" class="mode-select">
                <option value="METEOR-M2-3" selected>Meteor-M2-3 (137.900 MHz LRPT)</option>
                <option value="METEOR-M2-4">Meteor-M2-4 (137.900 MHz LRPT)</option>
-            </select>
-        </div>
+            </select>
+        </div>
        <div class="form-group">
            <label>Gain (dB)</label>
-            <input type="number" id="weatherSatGain" value="40" step="0.1" min="0" max="50">
+            <input type="number" id="weatherSatGain" value="30" step="0.1" min="0" max="50">
+            <p class="info-text" style="font-size: 10px; color: var(--text-dim); margin-top: 3px;">Reduce if decoding fails on strong passes (ADC saturation).</p>
        </div>
        <div class="form-group">
            <label style="display: flex; align-items: center; gap: 6px;">
@@ -69,7 +70,7 @@
                    <li><strong style="color: var(--text-primary);">Connection:</strong> Solder elements to coax center + shield, connect to SDR via SMA</li>
                </ul>
                <p style="margin-top: 6px; color: var(--text-dim); font-style: italic;">
-                    Best starter antenna. Good enough for a clean Meteor LRPT pass when the satellite gets high overhead.
+                    Best starter antenna. Good enough for a clean Meteor LRPT pass when the satellite gets high overhead.
                </p>
            </div>

@@ -132,8 +133,8 @@
                    <li><strong style="color: var(--text-primary);">Antenna up:</strong> Point the antenna straight UP (zenith) for best overhead coverage</li>
                    <li><strong style="color: var(--text-primary);">Avoid:</strong> Metal roofs, power lines, buildings blocking the sky</li>
                    <li><strong style="color: var(--text-primary);">Coax length:</strong> Keep short (&lt;10m). Signal loss at 137 MHz is ~3 dB per 10m of RG-58</li>
-                    <li><strong style="color: var(--text-primary);">LNA:</strong> Mount at the antenna feed point, NOT at the SDR end.
-                        Recommended: a low-noise 137 MHz filtered LNA near the antenna feed point</li>
+                    <li><strong style="color: var(--text-primary);">LNA:</strong> Mount at the antenna feed point, NOT at the SDR end.
+                        Recommended: a low-noise 137 MHz filtered LNA near the antenna feed point</li>
                    <li><strong style="color: var(--text-primary);">Bias-T:</strong> Enable the Bias-T checkbox above if your LNA is powered via the coax from the SDR</li>
                </ul>
            </div>
@@ -162,9 +163,9 @@
                        <td style="padding: 3px 4px; color: var(--text-dim);">Polarization</td>
                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">RHCP</td>
                    </tr>
-                    <tr>
-                        <td style="padding: 3px 4px; color: var(--text-dim);">Meteor (LRPT) bandwidth</td>
-                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">~140 kHz</td>
+                    <tr>
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Meteor (LRPT) bandwidth</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">~140 kHz</td>
                    </tr>
                </table>
            </div>
@@ -177,29 +178,29 @@
            <span class="wxsat-collapse-icon collapsed" style="font-size: 10px; transition: transform 0.2s; display: inline-block;">&#9660;</span>
        </h3>
        <div class="wxsat-test-decode-body collapsed" style="overflow: hidden;">
-            <p class="info-text" style="font-size: 11px; color: var(--text-dim); margin-bottom: 8px;">
-                Decode a pre-recorded Meteor IQ file without SDR hardware.
-                Shared ground-station recordings are also accepted by the backend.
-            </p>
-            <div class="form-group">
-                <label>Satellite</label>
-                <select id="wxsatTestSatSelect" class="mode-select">
-                    <option value="METEOR-M2-3" selected>Meteor-M2-3 (LRPT)</option>
-                    <option value="METEOR-M2-4">Meteor-M2-4 (LRPT)</option>
-                </select>
-            </div>
-            <div class="form-group">
-                <label>File Path (server-side)</label>
-                <input type="text" id="wxsatTestFilePath" value="data/weather_sat/samples/meteor_lrpt.sigmf-data" style="font-family: 'Roboto Condensed', 'Arial Narrow', sans-serif; font-size: 11px;">
-            </div>
-            <div class="form-group">
-                <label>Sample Rate</label>
-                <select id="wxsatTestSampleRate" class="mode-select">
-                    <option value="500000">500 kHz (IQ LRPT)</option>
-                    <option value="1000000">1 MHz (IQ narrow)</option>
-                    <option value="2400000" selected>2.4 MHz (INTERCEPT default)</option>
-                </select>
-            </div>
+            <p class="info-text" style="font-size: 11px; color: var(--text-dim); margin-bottom: 8px;">
+                Decode a pre-recorded Meteor IQ file without SDR hardware.
+                Shared ground-station recordings are also accepted by the backend.
+            </p>
+            <div class="form-group">
+                <label>Satellite</label>
+                <select id="wxsatTestSatSelect" class="mode-select">
+                    <option value="METEOR-M2-3" selected>Meteor-M2-3 (LRPT)</option>
+                    <option value="METEOR-M2-4">Meteor-M2-4 (LRPT)</option>
+                </select>
+            </div>
+            <div class="form-group">
+                <label>File Path (server-side)</label>
+                <input type="text" id="wxsatTestFilePath" value="data/weather_sat/samples/meteor_lrpt.sigmf-data" style="font-family: 'Roboto Condensed', 'Arial Narrow', sans-serif; font-size: 11px;">
+            </div>
+            <div class="form-group">
+                <label>Sample Rate</label>
+                <select id="wxsatTestSampleRate" class="mode-select">
+                    <option value="500000">500 kHz (IQ LRPT)</option>
+                    <option value="1000000">1 MHz (IQ narrow)</option>
+                    <option value="2400000" selected>2.4 MHz (INTERCEPT default)</option>
+                </select>
+            </div>
            <button class="mode-btn" onclick="WeatherSat.testDecode()" style="width: 100%; margin-top: 4px;">
                Test Decode
            </button>
@@ -226,12 +227,12 @@
    <div class="section">
        <h3>Resources</h3>
        <div style="display: flex; flex-direction: column; gap: 6px;">
-            <a href="https://github.com/SatDump/SatDump" target="_blank" rel="noopener" class="preset-btn" style="text-decoration: none; text-align: center;">
-                SatDump Documentation
-            </a>
-            <a href="https://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-meteor-m2-weather-satellite-images/" target="_blank" rel="noopener" class="preset-btn" style="text-decoration: none; text-align: center;">
-                Meteor Reception Guide
-            </a>
-        </div>
-    </div>
-</div>
+            <a href="https://github.com/SatDump/SatDump" target="_blank" rel="noopener" class="preset-btn" style="text-decoration: none; text-align: center;">
+                SatDump Documentation
+            </a>
+            <a href="https://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-meteor-m2-weather-satellite-images/" target="_blank" rel="noopener" class="preset-btn" style="text-decoration: none; text-align: center;">
+                Meteor Reception Guide
+            </a>
+        </div>
+    </div>
+</div>