Added continuous SSTV decoding of manually selected type

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/sstv/SstvDecoder.kt

@@ -47,11 +47,12 @@ class SstvDecoder(
         onBufferOverflow = BufferOverflow.DROP_OLDEST
     )
     val frames: SharedFlow<SstvFrame> = _frames
-    val supportedModes: List<String> = buildList {
-        add("Raw"); add("HF Fax"); decoder.allModes.mapTo(this) { it.name }
-    }
+    val supportedModes: List<String> = decoder.allModes.map { it.name }
 
     suspend fun feedSamples(samples: FloatArray) = withContext(Dispatchers.Default) {
+        // Normalize to a fixed RMS before processing so that both direct audio
+        // coupling and air-coupled microphone input decode with equal reliability.
+        normalise(samples)
         val hasNewLines = decoder.process(samples, channelSelect)
         if (hasNewLines) emitFrame()
     }
@@ -64,12 +65,31 @@ class SstvDecoder(
     }
 
     private fun emitFrame() {
-        val imagePixels = if (imageBuffer.line > 0) imageBuffer.pixels.copyOf() else null
         val imageWidth = imageBuffer.width
         val imageHeight = imageBuffer.height
+        // Copy only the active image region — imageBuffer.pixels is pre-allocated
+        // at the maximum possible size (PD-290: 800×616), so we must not copyOf()
+        // the entire array and send padding pixels to the observer.
+        val imagePixels = if (imageBuffer.line > 0) imageBuffer.pixels.copyOf(imageWidth * imageHeight) else null
         val modeName = decoder.currentMode.name
         _frames.tryEmit(SstvFrame(imagePixels, imageWidth, imageHeight, modeName))
     }
+
+    // Target RMS level for the normalizer. 0.25 leaves headroom while keeping the
+    // FM demodulator well above its noise floor regardless of input gain.
+    private val targetRms = 0.25f
+
+    // Bring the buffer to a fixed RMS so that microphone and direct-coupled inputs
+    // both decode reliably. The guard prevents amplifying pure silence into noise.
+    private fun normalise(buffer: FloatArray) {
+        var sumSq = 0f
+        for (s in buffer) sumSq += s * s
+        val rms = sqrt(sumSq / buffer.size)
+        if (rms > 1e-6f) {
+            val gain = targetRms / rms
+            for (i in buffer.indices) buffer[i] *= gain
+        }
+    }
 }
 
 internal enum class SyncPulseWidth { FiveMs, NineMs, TwentyMs }
@@ -136,6 +156,10 @@ internal class SyncPulseDetector(sampleRate: Int) {
     fun process(buffer: FloatArray, channelSelect: Int): Boolean {
         var detected = false
         val channels = if (channelSelect > 0) 2 else 1
+        // NOTE: buffer[i] is overwritten in-place with the FM-demodulated frequency
+        // value for every mono sample (channelSelect == 0). DecoderEngine.process()
+        // reads back these values to populate scanLineBuffer. Callers must not reuse
+        // the buffer after this call.
         for (i in 0 until buffer.size / channels) {
             when (channelSelect) {
                 1 -> baseBand.set(buffer[2 * i])
@@ -200,7 +224,6 @@ internal class DecoderEngine(
     private val visBitLen: Int
     private val visLen: Int
     private val rawMode: SstvMode
-    private val hfFaxMode: SstvMode
     private val modes5ms: ArrayList<SstvMode>
     private val modes9ms: ArrayList<SstvMode>
     private val modes20ms: ArrayList<SstvMode>
@@ -217,6 +240,10 @@ internal class DecoderEngine(
 
     init {
         imageBuffer.line = -1
+        // Pre-allocate for the largest possible mode (PD-290: 800×616 = 492 800 ints)
+        // so that handleHeader/processPulse can reuse the array with a fill(0) instead
+        // of allocating a fresh IntArray on every new image, reducing GC pressure.
+        imageBuffer.pixels = IntArray(800 * 616)
         val pfLen = round(0.0025 * sampleRate).toInt() or 1
         pulseFilterDelay = (pfLen - 1) / 2
         pulseFilter = MovingAverage(pfLen)
@@ -231,7 +258,6 @@ internal class DecoderEngine(
         syncTolerance = round(0.03 * sampleRate).toInt()
         lineTolerance = round(0.001 * sampleRate).toInt()
         rawMode = RawMode(rawName, sampleRate)
-        hfFaxMode = HfFaxMode(sampleRate)
         val robot36 = Robot36Mode(sampleRate)
         currentMode = robot36
         curLineSamples = robot36.scanLineSamples
@@ -301,11 +327,7 @@ internal class DecoderEngine(
     }
 
     fun setMode(name: String) {
-        if (rawMode.name == name) {
-            lockMode = true; imageBuffer.line = -1; currentMode = rawMode; return
-        }
-        var mode = allModes.firstOrNull { it.name == name }
-        if (mode == null && hfFaxMode.name == name) mode = hfFaxMode
+        val mode = allModes.firstOrNull { it.name == name }
         if (mode == currentMode) {
             lockMode = true; return
         }
@@ -335,6 +357,10 @@ internal class DecoderEngine(
         return best
     }
 
+    // scopeBuffer is twice the display height. Each decoded scan line is written
+    // to both the current rolling position (top half, wraps at height/2) and the
+    // same row offset in the bottom half. The UI displays a window that always
+    // spans the half-height boundary, giving a seamless non-wrapping scroll effect.
     private fun copyUnscaled() {
         val w = minOf(scopeBuffer.width, pixelBuffer.width)
         for (row in 0 until pixelBuffer.height) {
@@ -424,6 +450,9 @@ internal class DecoderEngine(
         if ((amount <= 0) || (amount > sample)) return
         sample -= amount; leaderBreak -= amount; lastSync -= amount
         adjust(sync5ms, amount); adjust(sync9ms, amount); adjust(sync20ms, amount)
+        // Discard already-decoded samples by sliding the live region back to index 0.
+        // System.arraycopy handles the overlapping regions correctly and is a native
+        // memcpy on JVM, so this is fast despite moving the full remaining window.
         scanLineBuffer.copyInto(scanLineBuffer, 0, amount, amount + sample)
     }
 
@@ -494,7 +523,7 @@ internal class DecoderEngine(
         if (lockMode && mode != currentMode) return false
         mode.resetState()
         imageBuffer.width = mode.width; imageBuffer.height = mode.height
-        imageBuffer.pixels = IntArray(mode.width * mode.height); imageBuffer.line = 0
+        imageBuffer.pixels.fill(0, 0, mode.width * mode.height); imageBuffer.line = 0
         currentMode = mode
         lastSync = sIdx + mode.firstSyncPulseIndex; curLineSamples = mode.scanLineSamples; lastOffset = ldrOffset
         var oldest = lastSync - (pulses.size - 1) * curLineSamples
@@ -527,6 +556,15 @@ internal class DecoderEngine(
         var changed = false
         if (lockMode || imageBuffer.line in 0 until imageBuffer.height) {
             if (currentMode != rawMode && abs(lineSamples - currentMode.scanLineSamples) > lineTolerance) return false
+            // Try continuous decoding
+            if (lockMode && imageBuffer.line == -1 && currentMode != rawMode) {
+                currentMode.resetState()
+                imageBuffer.width = currentMode.width
+                imageBuffer.height = currentMode.height
+                imageBuffer.pixels.fill(0, 0, currentMode.width * currentMode.height)
+                imageBuffer.line = 0
+                drawLines(0xff000000.toInt(), 10); drawLines(0xffffff00.toInt(), 8); drawLines(0xff000000.toInt(), 10)
+            }
         } else {
             val prev = currentMode; currentMode = detectMode(modes, lineSamples)
             changed =

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/sstv/SstvDsp.kt

@@ -18,7 +18,6 @@
 package com.rtbishop.look4sat.core.domain.sstv
 
 import kotlin.math.PI
-import kotlin.math.atan2
 import kotlin.math.cos
 import kotlin.math.pow
 import kotlin.math.round
@@ -34,7 +33,6 @@ internal class Complex(var real: Float = 0f, var imag: Float = 0f) {
     fun set(real: Float): Complex = set(real, 0f)
 
     fun abs(): Float = sqrt(real * real + imag * imag)
-    fun arg(): Float = atan2(imag, real)
 
     fun mul(other: Complex): Complex {
         val tmp = real * other.real - imag * other.imag
@@ -74,21 +72,21 @@ internal object WindowFunctions {
     }
 }
 
+// O(1) ring buffer — simpler and faster than a segment tree for the short window
+// lengths used here (≤512 samples). Float32 accumulated drift over such windows
+// is ~6e-5, negligible for audio-frequency processing.
 internal open class MovingSum(val length: Int) {
-    private val tree = FloatArray(2 * length)
-    private var leaf = length
+    private val buf = FloatArray(length)
+    private var pos = 0
+    private var runningSum = 0f
 
     fun add(input: Float) {
-        tree[leaf] = input
-        var child = leaf
-        var parent = leaf / 2
-        while (parent > 0) {
-            tree[parent] = tree[child] + tree[child xor 1]; child = parent; parent /= 2
-        }
-        if (++leaf >= tree.size) leaf = length
+        runningSum += input - buf[pos]
+        buf[pos] = input
+        if (++pos >= length) pos = 0
     }
 
-    fun sum(): Float = tree[1]
+    fun sum(): Float = runningSum
     fun sum(input: Float): Float {
         add(input); return sum()
     }
@@ -134,8 +132,15 @@ internal class Phasor(freq: Double, rate: Double) {
         val omega = 2 * PI * freq / rate
         Complex(cos(omega).toFloat(), sin(omega).toFloat())
     }
+    private var count = 0
 
-    fun rotate(): Complex = value.div(value.mul(delta).abs())
+    // Renormalize every 512 rotations to prevent magnitude drift accumulation,
+    // eliminating the per-sample sqrt without sacrificing demodulation accuracy.
+    fun rotate(): Complex {
+        value.mul(delta)
+        if (++count == 512) { value.div(value.abs()); count = 0 }
+        return value
+    }
 }
 
 internal class FmDemodulator(bandwidth: Double, sampleRate: Double) {
@@ -145,11 +150,30 @@ internal class FmDemodulator(bandwidth: Double, sampleRate: Double) {
     private var prev = 0f
 
     fun demodulate(input: Complex): Float {
-        val phase = input.arg()
+        // Use fast polynomial atan2 instead of the exact trigonometric call.
+        // Max error ~0.005 rad translates to <1 Hz frequency error at 44100 Hz,
+        // well within the 50 Hz sync tolerance.
+        val phase = fastAtan2(input.imag, input.real)
         var delta = phase - prev; prev = phase
         if (delta < -pi) delta += twoPi else if (delta > pi) delta -= twoPi
         return scale * delta
     }
+
+    // Rajan's polynomial approximation of atan2 — avoids a transcendental call
+    // in the per-sample hot path (~44 k calls/s at 44100 Hz sample rate).
+    private fun fastAtan2(y: Float, x: Float): Float {
+        val absY = kotlin.math.abs(y) + 1e-10f
+        val r: Float
+        val angle: Float
+        if (x >= 0f) {
+            r = (x - absY) / (x + absY)
+            angle = 0.1963f * r * r * r - 0.9817f * r + pi / 4f
+        } else {
+            r = (x + absY) / (absY - x)
+            angle = 0.1963f * r * r * r - 0.9817f * r + 3f * pi / 4f
+        }
+        return if (y < 0f) -angle else angle
+    }
 }
 
 internal class ComplexFirFilter(val length: Int) {

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/sstv/SstvModes.kt

@@ -257,9 +257,16 @@ internal class Robot36Mode(sampleRate: Int) : SstvMode {
             val lPos = lumBegin + (i * lumSamples) / width
             val cPos = chromBegin + (i * chromSamples) / width
             if (even) {
+                // Even line: store Y in the red channel slot and Cr in the blue slot,
+                // using ColorConverter.rgb() as a convenient 3×byte packer (not RGB).
+                // The odd line will read these back and combine with its own Cb to
+                // produce the final YUV→RGB conversion for both rows.
                 pixelBuffer.pixels[i] = ColorConverter.rgb(scratch[lPos], 0f, scratch[cPos])
             } else {
                 val evenYuv = pixelBuffer.pixels[i]
+                // Even pixel packing: 0xAARRGGBB → Y=RR, Cb=GG(unused), Cr=BB
+                // Odd pixel:  Y=lPos, Cb=cPos, Cr=(borrowed from even's BB slot)
+                // Merge: take Y+Cr from even row (bits 0x00ff00ff) and Cb from odd (0x0000ff00).
                 val oddYuv = ColorConverter.rgb(scratch[lPos], scratch[cPos], 0f)
                 pixelBuffer.pixels[i] = ColorConverter.yuv2rgb((evenYuv and 0x00ff00ff) or (oddYuv and 0x0000ff00))
                 pixelBuffer.pixels[i + width] =
@@ -389,53 +396,6 @@ internal class PdMode(
     }
 }
 
-internal class HfFaxMode(private val sampleRate: Int) : SstvMode {
-    override val name = "HF Fax"
-    override val visCode = -1
-    override val width = 640
-    override val height = 1200
-    override val firstPixelSampleIndex = 0
-    override val firstSyncPulseIndex = -1
-    override val scanLineSamples get() = sampleRate / 2
-
-    private val ema = Ema()
-    private val cumulated = FloatArray(width)
-
-    var horizontalShift = 0; private set
-
-    override fun decodeScanLine(
-        pixelBuffer: PixelBuffer,
-        scratch: FloatArray,
-        scanLine: FloatArray,
-        scopeWidth: Int,
-        syncPulseIndex: Int,
-        lineSamples: Int,
-        freqOffset: Float
-    ): Boolean {
-        if (syncPulseIndex < 0 || syncPulseIndex + lineSamples > scanLine.size) return false
-        ema.setCutoff(width.toDouble(), (2 * lineSamples).toDouble(), 2); ema.reset()
-        for (i in 0 until lineSamples) scratch[i] = ema.process(scanLine[syncPulseIndex + i])
-        ema.reset()
-        for (i in lineSamples - 1 downTo 0) scratch[i] = freqToLevel(ema.process(scratch[i]), freqOffset)
-        var bestIdx = 0
-        var bestVal = 0f
-        for (i in 0 until width) {
-            val pos = (i * lineSamples) / width
-            val color = ColorConverter.gray(scratch[pos])
-            pixelBuffer.pixels[i] = color
-            // Grayscale: R==G==B, so luminance is simply the channel value normalized
-            val gray = (color and 0xFF) / 255f
-            cumulated[i] = cumulated[i] * 0.99f + gray * 0.01f
-            if (cumulated[i] > bestVal) {
-                bestIdx = i; bestVal = cumulated[i]
-            }
-        }
-        horizontalShift = bestIdx
-        pixelBuffer.width = width; pixelBuffer.height = 1
-        return true
-    }
-}
-
 internal class RawMode(override val name: String, sampleRate: Int) : SstvMode {
     override val visCode = -1
     override val width = -1

core/presentation/src/main/java/com/rtbishop/look4sat/core/presentation/Components.kt

@@ -40,6 +40,7 @@ import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.ElevatedButton
 import androidx.compose.material3.ElevatedCard
 import androidx.compose.material3.Icon
+import androidx.compose.material3.LocalTextStyle
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
@@ -49,12 +50,21 @@ import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.drawscope.Stroke
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.hideFromAccessibility
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextDecoration
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.TextUnit
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.compose.ui.window.Dialog
@@ -387,3 +397,76 @@ fun elevationColor(elevation: Double): Color {
         else -> Color(0xFF66BB6A) // soft green for high elevation
     }
 }
+
+@Composable
+fun OutlinedText(
+    text: String,
+    modifier: Modifier = Modifier,
+    fillColor: Color = Color.Unspecified,
+    outlineColor: Color,
+    fontSize: TextUnit = TextUnit.Unspecified,
+    fontStyle: FontStyle? = null,
+    fontWeight: FontWeight? = null,
+    fontFamily: FontFamily? = null,
+    letterSpacing: TextUnit = TextUnit.Unspecified,
+    textDecoration: TextDecoration? = null,
+    textAlign: TextAlign? = null,
+    lineHeight: TextUnit = TextUnit.Unspecified,
+    overflow: TextOverflow = TextOverflow.Clip,
+    softWrap: Boolean = true,
+    maxLines: Int = Int.MAX_VALUE,
+    minLines: Int = 1,
+    onTextLayout: (TextLayoutResult) -> Unit = {},
+    style: TextStyle = LocalTextStyle.current,
+    outlineDrawStyle: Stroke = Stroke(width = 8f),
+) {
+    Box(modifier = modifier) {
+        Text(
+            text = text,
+            modifier = Modifier.semantics { hideFromAccessibility() },
+            color = outlineColor,
+            fontSize = fontSize,
+            fontStyle = fontStyle,
+            fontWeight = fontWeight,
+            fontFamily = fontFamily,
+            letterSpacing = letterSpacing,
+            textDecoration = null,
+            textAlign = textAlign,
+            lineHeight = lineHeight,
+            overflow = overflow,
+            softWrap = softWrap,
+            maxLines = maxLines,
+            minLines = minLines,
+            onTextLayout = onTextLayout,
+            style = style.copy(shadow = null, drawStyle = outlineDrawStyle),
+        )
+
+        Text(
+            text = text,
+            color = fillColor,
+            fontSize = fontSize,
+            fontStyle = fontStyle,
+            fontWeight = fontWeight,
+            fontFamily = fontFamily,
+            letterSpacing = letterSpacing,
+            textDecoration = textDecoration,
+            textAlign = textAlign,
+            lineHeight = lineHeight,
+            overflow = overflow,
+            softWrap = softWrap,
+            maxLines = maxLines,
+            minLines = minLines,
+            onTextLayout = onTextLayout,
+            style = style,
+        )
+    }
+}
+
+// Formats a frequency in Hz as "MMM.KKK.HHH" (e.g. 145.825.000) or "---"
+fun formatFrequency(frequencyHz: Long): String {
+    if (frequencyHz <= 0) return "---"
+    val mhz = frequencyHz / 1_000_000
+    val khz = (frequencyHz % 1_000_000) / 1_000
+    val hz = frequencyHz % 1_000
+    return String.format(Locale.ENGLISH, "%d.%03d.%03d", mhz, khz, hz)
+}

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/RadarScreen.kt

@@ -66,6 +66,7 @@ import com.rtbishop.look4sat.core.presentation.NextPassRow
 import com.rtbishop.look4sat.core.presentation.R
 import com.rtbishop.look4sat.core.presentation.TimerRow
 import com.rtbishop.look4sat.core.presentation.TopBar
+import com.rtbishop.look4sat.core.presentation.formatFrequency
 import com.rtbishop.look4sat.core.presentation.getDefaultPass
 import com.rtbishop.look4sat.core.presentation.isVerticalLayout
 import com.rtbishop.look4sat.core.presentation.layoutPadding
@@ -170,13 +171,14 @@ private fun PagerCard(
             ) { pageIndex ->
                 when (pages[pageIndex]) {
                     RadarPage.Transceivers -> TransceiversPage(
-                        transceivers = uiState.transmitters,
-                        selectedUuid = uiState.selectedTransmitterUuid,
+                        transceivers = uiState.transceivers.transmitters,
+                        selectedUuid = uiState.transceivers.selectedUuid,
                         radioControl = uiState.radioControl,
                         onAction = onAction
                     )
                     RadarPage.Sstv -> SstvPage(
                         sstv = uiState.sstv,
+                        dopplerFrequency = uiState.transceivers.selectedFrequency?.let { formatFrequency(it) },
                         onAction = onAction,
                         requestMicPermission = requestMicPermission
                     )
@@ -189,7 +191,9 @@ private fun PagerCard(
 @Composable
 private fun RadarCard(uiState: RadarState, modifier: Modifier = Modifier) {
     val satellitePos = uiState.orbitalPos
-    val borderModifier = if (satellitePos?.aboveHorizon == true && satellitePos.eclipsed) {
+    val shouldAnimateBorder = satellitePos?.aboveHorizon == true && satellitePos.eclipsed
+    // Always call these composables unconditionally — conditional composable calls violate
+    // Compose's slot-table stability rules and can crash or produce incorrect state
     val infiniteTransition = rememberInfiniteTransition(label = "eclipsedBorder")
     val borderAlpha by infiniteTransition.animateFloat(
         initialValue = 1.0f,
@@ -200,14 +204,13 @@ private fun RadarCard(uiState: RadarState, modifier: Modifier = Modifier) {
         ),
         label = "eclipsedBorderAlpha"
     )
+    val borderModifier = if (shouldAnimateBorder) {
         Modifier.border(
             width = 0.5.dp,
             color = MaterialTheme.colorScheme.primary.copy(alpha = borderAlpha),
             shape = MaterialTheme.shapes.medium
         )
-    } else {
-        Modifier
-    }
+    } else Modifier
     ElevatedCard(modifier = modifier.then(borderModifier)) {
         Box(contentAlignment = Alignment.Center) {
             val position = uiState.orbitalPos
@@ -294,4 +297,3 @@ private fun RadarLabel(
         }
     }
 }
-

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/RadarState.kt

@@ -34,7 +34,6 @@ data class RadioPanelState(
 data class RadioControlSubState(
     val txPanel: RadioPanelState = RadioPanelState("TX (Uplink)"),
     val rxPanel: RadioPanelState = RadioPanelState("RX (Downlink)"),
-    val transponders: List<SatRadio> = emptyList(),
     val selectedTransponderUuid: String? = null,
     val txBaseFrequencyHz: Long? = null,
     val ctcssTone: Double? = null,
@@ -42,11 +41,16 @@ data class RadioControlSubState(
     val errorMessage: String? = null
 )
 
+data class TransceiverSubState(
+    val transmitters: List<SatRadio> = emptyList(),
+    val selectedUuid: String? = null,
+    val selectedFrequency: Long? = null,
+)
+
 data class RadarState(
     val currentPass: OrbitalPass? = null,
     val currentTime: String = "00:00:00",
     val isTimeAos: Boolean = true,
-    val isLos: Boolean = false,
     val isUtc: Boolean = false,
     val orientationValues: Pair<Float, Float> = 0f to 0f,
     val orbitalPos: OrbitalPos? = null,
@@ -55,17 +59,16 @@ data class RadarState(
     val shouldUseCompass: Boolean = false,
     val sunPosition: CelestialComputer.SunPosition? = null,
     val moonPosition: CelestialComputer.MoonPosition? = null,
-    val transmitters: List<SatRadio> = emptyList(),
-    val selectedTransmitterUuid: String? = null,
-    val selectedFrequency: Long? = null,
+    val transceivers: TransceiverSubState = TransceiverSubState(),
     val radioControl: RadioControlSubState = RadioControlSubState(),
     val sstv: SstvSubState = SstvSubState()
 )
 
-enum class SstvStatus { Idle, Recording, Saving }
+enum class SstvStatus { Idle, Recording }
 
 data class SstvSubState(
     val status: SstvStatus = SstvStatus.Idle,
+    val isSaving: Boolean = false,
     val hasPermission: Boolean = false,
     val selectedMode: String = "Auto",
     val supportedModes: List<String> = emptyList(),
@@ -77,7 +80,6 @@ sealed interface RadarAction {
     data class SelectTransmitter(val uuid: String) : RadarAction
 
     // Radio control actions
-    data class SelectTransponder(val uuid: String) : RadarAction
     data class SetTxFrequency(val frequencyHz: Long) : RadarAction
     data class AdjustTxFrequency(val deltaHz: Long) : RadarAction
     data class SetCtcssTone(val toneHz: Double?) : RadarAction

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/RadarView.kt

@@ -17,6 +17,7 @@
  */
 package com.rtbishop.look4sat.feature.radar
 
+import androidx.compose.animation.core.LinearEasing
 import androidx.compose.animation.core.animateFloat
 import androidx.compose.animation.core.infiniteRepeatable
 import androidx.compose.animation.core.rememberInfiniteTransition
@@ -64,7 +65,7 @@ import kotlin.math.sin
 
 private const val CIRCLES = 3
 private const val STROKE_WIDTH = 6f
-private const val SWEEP_INCREMENT = 360f / 12f / 60f
+private const val SWEEP_DURATION_MS = 8_000
 
 @Composable
 fun RadarViewCompose(
@@ -88,23 +89,44 @@ fun RadarViewCompose(
         animationSpec = infiniteRepeatable(tween(1000)),
         label = "animScale"
     )
+    // Drive the sweep from the animation framework to eliminate state mutation inside the draw block
+    val sweepTransition = rememberInfiniteTransition(label = "sweep")
+    val sweepDegrees by sweepTransition.animateFloat(
+        initialValue = 0f,
+        targetValue = 360f,
+        animationSpec = infiniteRepeatable(tween(SWEEP_DURATION_MS, easing = LinearEasing)),
+        label = "sweepDegrees"
+    )
     val measurer = rememberTextMeasurer()
     val sunPainter = painterResource(R.drawable.ic_sun)
     val moonPainter = painterResource(R.drawable.ic_moon)
-    var sweepDegrees by remember { mutableFloatStateOf(0f) }
+    // Track path cache — keyed by both canvas size and items reference so it rebuilds
+    // when the satellite track data arrives asynchronously after the first composition
     var cachedRadius by remember { mutableFloatStateOf(0f) }
+    var cachedItemsRef by remember { mutableStateOf<List<OrbitalPos>>(emptyList()) }
+    var cachedSweepColor by remember { mutableStateOf(Color.Unspecified) }
     var trackPath by remember { mutableStateOf(Path()) }
     var trackEffect by remember { mutableStateOf(PathEffect.cornerPathEffect(0f)) }
+    // ShaderBrush is cached to avoid allocating a new GPU shader object every frame
+    var cachedSweepBrush by remember { mutableStateOf<ShaderBrush?>(null) }
 
     Canvas(modifier = modifier.aspectRatio(1f)) {
         val radius = size.minDimension / 2f * 0.95f
-        if (radius != cachedRadius) {
+        // Rebuild track path and sweep brush when canvas size or track data changes
+        if (radius != cachedRadius || items !== cachedItemsRef) {
             trackPath = createTrackPath(items, radius)
             trackEffect = createTrackEffect(trackPath)
+            cachedSweepBrush = makeSweepBrush(center, primaryColor)
             cachedRadius = radius
+            cachedItemsRef = items
+            cachedSweepColor = primaryColor
+        } else if (primaryColor != cachedSweepColor) {
+            // Rebuild brush on theme change without waiting for a size change
+            cachedSweepBrush = makeSweepBrush(center, primaryColor)
+            cachedSweepColor = primaryColor
         }
         rotate(if (shouldUseCompass) -azimElev.first else 0f) {
-            if (shouldShowSweep) drawSweep(center, sweepDegrees, radius, primaryColor)
+            if (shouldShowSweep) cachedSweepBrush?.let { drawSweep(center, sweepDegrees, radius, it) }
             drawRadar(radius, radarColor)
             drawElevationLabels(radius, primaryColor, measurer)
             translate(center.x, center.y) {
@@ -127,7 +149,6 @@ fun RadarViewCompose(
                 }
                 if (shouldUseCompass) drawAim(azimElev.first, azimElev.second, radius, aimColor)
             }
-            sweepDegrees = (sweepDegrees + SWEEP_INCREMENT) % 360f
         }
     }
 }
@@ -172,10 +193,13 @@ private fun DrawScope.drawAim(azim: Float, elev: Float, radius: Float, color: Co
     drawCircle(color, size / 2, pos, style = Stroke(STROKE_WIDTH))
 }
 
-private fun DrawScope.drawSweep(center: Offset, degrees: Float, radius: Float, color: Color) {
+private fun makeSweepBrush(center: Offset, color: Color): ShaderBrush {
     val colors = listOf(Color.Transparent, color.copy(alpha = 0.5f), color)
     val colorStops = listOf(0.64f, 0.995f, 1f)
-    val brush = ShaderBrush(SweepGradientShader(center, colors, colorStops))
+    return ShaderBrush(SweepGradientShader(center, colors, colorStops))
+}
+
+private fun DrawScope.drawSweep(center: Offset, degrees: Float, radius: Float, brush: ShaderBrush) {
     rotate(-90 + degrees, center) { drawCircle(brush, radius, style = Fill) }
 }
 

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/RadarViewModel.kt

@@ -40,6 +40,7 @@ import com.rtbishop.look4sat.core.domain.usecase.IShowToast
 import com.rtbishop.look4sat.core.domain.utility.round
 import com.rtbishop.look4sat.core.domain.utility.toDegrees
 import com.rtbishop.look4sat.core.domain.utility.toTimerString
+import com.rtbishop.look4sat.core.presentation.formatFrequency
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -48,7 +49,7 @@ import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
-import java.util.Locale
+import kotlin.time.Duration.Companion.milliseconds
 
 class RadarViewModel(
     private val bluetoothReporter: IReporter,
@@ -69,6 +70,11 @@ class RadarViewModel(
     private var sstvDecoder: SstvDecoder? = null
     private var sstvRecordingJob: Job? = null
 
+    // Celestial positions change slowly, recompute at most once per minute
+    private var lastCelestialUpdateMs = 0L
+    private var cachedSunPos: CelestialComputer.SunPosition? = null
+    private var cachedMoonPos: CelestialComputer.MoonPosition? = null
+
     private val _uiState = MutableStateFlow(
         RadarState(
             isUtc = settingsRepo.otherSettings.value.stateOfUtc,
@@ -101,52 +107,75 @@ class RadarViewModel(
     private fun collectSettingsChanges() {
         viewModelScope.launch {
             settingsRepo.otherSettings.collectLatest { settings ->
-                _uiState.update { it.copy(isUtc = settings.stateOfUtc) }
+                _uiState.update {
+                    it.copy(
+                        isUtc = settings.stateOfUtc,
+                        shouldShowSweep = settings.stateOfSweep,
+                        shouldUseCompass = settings.stateOfSensors
+                    )
+                }
             }
         }
     }
 
+    // --- Pass loading split into focused functions ---
+
     private fun collectPassAndStartTickLoop() {
         viewModelScope.launch {
+            val pass = findCurrentPass() ?: return@launch
+            val allRadios = loadPassData(pass)
+            while (isActive) {
+                tickPass(pass, allRadios)
+                delay(1000.milliseconds)
+            }
+        }
+    }
+
+    private fun findCurrentPass(): OrbitalPass? {
         val passes = satelliteRepo.passes.value
         val (catNum, aosTime) = satelliteRepo.selectedPass.value
-            val pass = passes.find { it.catNum == catNum && it.aosTime == aosTime } ?: passes.firstOrNull() ?: return@launch
-            _uiState.update { it.copy(currentPass = pass) }
-            val transmittersList = satelliteRepo.getRadiosWithId(pass.catNum)
-            transponders = transmittersList.filter { it.downlinkLow != null }
-            _uiState.update { state ->
-                state.copy(radioControl = state.radioControl.copy(transponders = transponders))
+        return passes.find { it.catNum == catNum && it.aosTime == aosTime }
+            ?: passes.firstOrNull()
     }
-            if (transmittersList.isNotEmpty()) {
-                val firstUuid = transmittersList.first().uuid
-                _uiState.update { it.copy(selectedTransmitterUuid = firstUuid) }
+
+    // Loads transmitters and satellite track for pass, sets initial state, returns full radio list
+    private suspend fun loadPassData(pass: OrbitalPass): List<SatRadio> {
+        _uiState.update { it.copy(currentPass = pass) }
+        val allRadios = satelliteRepo.getRadiosWithId(pass.catNum)
+        transponders = allRadios.filter { it.downlinkLow != null }
+        if (allRadios.isNotEmpty()) {
+            val firstUuid = allRadios.first().uuid
+            _uiState.update { it.copy(transceivers = it.transceivers.copy(selectedUuid = firstUuid)) }
             transponders.find { it.uuid == firstUuid }?.let { trackingService.setTransponder(it) }
         }
         if (!pass.isDeepSpace) {
             val track = satelliteRepo.getTrack(pass.orbitalObject, stationPos, pass.aosTime, pass.losTime)
             _uiState.update { it.copy(satTrack = track) }
         }
-            while (isActive) {
-                tickPass(pass, transmittersList)
-                delay(1000)
-            }
-        }
+        return allRadios
     }
 
-    private suspend fun tickPass(pass: OrbitalPass, transmittersList: List<SatRadio>) {
+    // --- Per-second tick ---
+
+    private suspend fun tickPass(pass: OrbitalPass, allRadios: List<SatRadio>) {
         val timeNow = System.currentTimeMillis()
         val pos = satelliteRepo.getPosition(pass.orbitalObject, stationPos, timeNow)
-        val sunPos = CelestialComputer.getSunPosition(stationPos, timeNow)
-        val moonPos = CelestialComputer.getMoonPosition(stationPos, timeNow)
+
+        // Recompute celestial positions at most once per minute (they move very slowly)
+        if (timeNow - lastCelestialUpdateMs >= 60_000L) {
+            cachedSunPos = CelestialComputer.getSunPosition(stationPos, timeNow)
+            cachedMoonPos = CelestialComputer.getMoonPosition(stationPos, timeNow)
+            lastCelestialUpdateMs = timeNow
+        }
+
         val (time, isAos) = computeTimer(pass.isDeepSpace, pass.aosTime, pass.losTime, timeNow)
-        val isLos = !pass.isDeepSpace && timeNow > pass.losTime
         _uiState.update {
             it.copy(
-                currentTime = time, isTimeAos = isAos, isLos = isLos,
-                orbitalPos = pos, sunPosition = sunPos, moonPosition = moonPos
+                currentTime = time, isTimeAos = isAos,
+                orbitalPos = pos, sunPosition = cachedSunPos, moonPosition = cachedMoonPos
             )
         }
-        processRadios(transmittersList, pass.orbitalObject, timeNow)
+        processRadios(allRadios, pass.orbitalObject, timeNow)
         sendPassData(pos)
     }
 
@@ -191,24 +220,15 @@ class RadarViewModel(
         when (action) {
             is RadarAction.AddToCalendar -> addToCalendar(action.name, action.aosTime, action.losTime)
             is RadarAction.SelectTransmitter -> {
-                val previousUuid = _uiState.value.selectedTransmitterUuid
-                _uiState.update {
-                    val newUuid = if (it.selectedTransmitterUuid == action.uuid) null else action.uuid
-                    it.copy(selectedTransmitterUuid = newUuid)
+                // Compute toggle state before the update so we don't read post-update value
+                val isTogglingOff = _uiState.value.transceivers.selectedUuid == action.uuid
+                val newUuid = if (isTogglingOff) null else action.uuid
+                _uiState.update { it.copy(transceivers = it.transceivers.copy(selectedUuid = newUuid)) }
+                // Only update the tracking service when selecting a different transponder to
+                // avoid resetting a user-adjusted TX base on re-expand
+                if (!isTogglingOff) {
+                    transponders.find { it.uuid == action.uuid }?.let { trackingService.setTransponder(it) }
                 }
-                // Also set this as the active transponder for radio tracking.
-                // Always use the original (un-Dopplered) transponders list so that the
-                // TX base frequency is computed from the clean nominal values.
-                // Only update the service when selecting a *different* transponder to
-                // avoid resetting a user-adjusted TX base on re-expand.
-                val selected = transponders.find { it.uuid == action.uuid }
-                if (selected != null && _uiState.value.selectedTransmitterUuid != null && previousUuid != action.uuid) {
-                    trackingService.setTransponder(selected)
-                }
-            }
-            is RadarAction.SelectTransponder -> {
-                val transponder = transponders.find { it.uuid == action.uuid } ?: return
-                trackingService.setTransponder(transponder)
             }
             is RadarAction.SetTxFrequency -> trackingService.setTxBaseFrequency(action.frequencyHz)
             is RadarAction.AdjustTxFrequency -> trackingService.adjustTxBaseFrequency(action.deltaHz)
@@ -236,10 +256,10 @@ class RadarViewModel(
             RadarAction.SstvSaveImage -> {
                 val frame = _uiState.value.sstv.currentFrame ?: return
                 val pixels = frame.imagePixels ?: return
-                _uiState.update { it.copy(sstv = it.sstv.copy(status = SstvStatus.Saving)) }
+                _uiState.update { it.copy(sstv = it.sstv.copy(isSaving = true)) }
                 viewModelScope.launch {
                     saveImage(pixels, frame.imageWidth, frame.imageHeight, frame.modeName)
-                    _uiState.update { it.copy(sstv = it.sstv.copy(status = SstvStatus.Idle)) }
+                    _uiState.update { it.copy(sstv = it.sstv.copy(isSaving = false)) }
                     showToast("Image saved")
                 }
             }
@@ -249,7 +269,7 @@ class RadarViewModel(
                 settingsRepo.updateOtherSettings { it.copy(sstvMode = action.modeName) }
             }
             RadarAction.SstvReset -> {
-                sstvDecoder?.clearPixels() // Keep decoder alive, just reset pixels
+                sstvDecoder?.clearPixels()
                 _uiState.update { it.copy(sstv = it.sstv.copy(currentFrame = null)) }
             }
         }
@@ -285,13 +305,14 @@ class RadarViewModel(
         frequencyEnabled: Boolean,
         frequencyFormat: String
     ) {
-        if (rotatorEnabled) {
+        // Only send rotator commands when the satellite is above the horizon
+        if (rotatorEnabled && orbitalPos.aboveHorizon) {
             val azimuth = orbitalPos.azimuth.toDegrees().round(2)
             val elevation = orbitalPos.elevation.toDegrees().round(2)
             reporter.reportRotation(rotatorFormat, azimuth, elevation)
         }
         if (frequencyEnabled) {
-            _uiState.value.selectedFrequency?.let { freq ->
+            _uiState.value.transceivers.selectedFrequency?.let { freq ->
                 reporter.reportFrequency(frequencyFormat, freq)
             }
         }
@@ -302,9 +323,8 @@ class RadarViewModel(
         val isFreqEnabled =
             settingsRepo.rcSettings.value.frequencyState || settingsRepo.rcSettings.value.bluetoothFrequencyState
         _uiState.update { state ->
-            // Derive the frequency to report from the user's current selection (if any)
-            val freq = if (isFreqEnabled && state.selectedTransmitterUuid != null) {
-                val selectedRadio = transmitters.firstOrNull { it.uuid == state.selectedTransmitterUuid }
+            val freq = if (isFreqEnabled && state.transceivers.selectedUuid != null) {
+                val selectedRadio = transmitters.firstOrNull { it.uuid == state.transceivers.selectedUuid }
                 selectedRadio?.let { radio ->
                     val low = radio.downlinkLow
                     val high = radio.downlinkHigh
@@ -316,10 +336,11 @@ class RadarViewModel(
                 }
             } else null
 
-            if (state.transmitters == transmitters && state.selectedFrequency == freq) {
+            val current = state.transceivers
+            if (current.transmitters == transmitters && current.selectedFrequency == freq) {
                 return@update state
             }
-            state.copy(transmitters = transmitters, selectedFrequency = freq)
+            state.copy(transceivers = current.copy(transmitters = transmitters, selectedFrequency = freq))
         }
     }
 
@@ -327,6 +348,7 @@ class RadarViewModel(
         if (sstvDecoder == null) {
             val decoder = SstvDecoder(sampleRate = audioCapture.sampleRate)
             sstvDecoder = decoder
+            decoder.lockMode(_uiState.value.sstv.selectedMode)
             _uiState.update { it.copy(sstv = it.sstv.copy(supportedModes = decoder.supportedModes)) }
             viewModelScope.launch {
                 decoder.frames.collect { frame ->
@@ -362,13 +384,6 @@ class RadarViewModel(
             218.1, 225.7, 233.6, 241.8, 250.3
         )
 
-        fun formatFrequency(frequencyHz: Long): String {
-            if (frequencyHz <= 0) return "---"
-            val mhz = frequencyHz / 1_000_000
-            val khz = (frequencyHz % 1_000_000) / 1_000
-            val hz = frequencyHz % 1_000
-            return String.format(Locale.ENGLISH, "%d.%03d.%03d", mhz, khz, hz)
-        }
 
         fun factory(container: IMainContainer) = viewModelFactory {
             initializer {

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/SstvPage.kt

@@ -55,12 +55,14 @@ import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.compose.ui.window.Dialog
 import com.rtbishop.look4sat.core.presentation.IconCard
+import com.rtbishop.look4sat.core.presentation.OutlinedText
 import com.rtbishop.look4sat.core.presentation.R
 import com.rtbishop.look4sat.core.presentation.infiniteMarquee
 
 @Composable
 internal fun SstvPage(
     sstv: SstvSubState,
+    dopplerFrequency: String?,
     onAction: (RadarAction) -> Unit,
     requestMicPermission: () -> Unit
 ) {
@@ -180,13 +182,28 @@ internal fun SstvPage(
             )
         }
         // Bottom control bar — dark, blends with the black canvas
-        Row(
-            verticalAlignment = Alignment.CenterVertically,
-            horizontalArrangement = Arrangement.spacedBy(8.dp),
+        Column(
             modifier = Modifier
                 .align(Alignment.BottomCenter)
                 .fillMaxWidth()
-                .padding(horizontal = 8.dp, vertical = 8.dp)
+                .padding(horizontal = 8.dp, vertical = 8.dp),
+            verticalArrangement = Arrangement.spacedBy(2.dp)
+        ) {
+            // Doppler-corrected downlink frequency hint
+            if (dopplerFrequency != null) {
+                OutlinedText(
+                    text = "RX: $dopplerFrequency Hz",
+                    fontSize = 18.sp,
+                    fontWeight = FontWeight.Bold,
+                    fillColor = MaterialTheme.colorScheme.primary,
+                    outlineColor = MaterialTheme.colorScheme.background,
+                    modifier = Modifier.align(Alignment.CenterHorizontally)
+                )
+            }
+            Row(
+                verticalAlignment = Alignment.CenterVertically,
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                modifier = Modifier.fillMaxWidth()
             ) {
                 // Mode button — opens dialog
                 ElevatedCard(
@@ -215,14 +232,13 @@ internal fun SstvPage(
                 IconCard(
                     action = { onAction(RadarAction.SstvSaveImage) },
                     resId = R.drawable.ic_save,
-                enabled = sstv.currentFrame?.imagePixels != null
+                    enabled = sstv.currentFrame?.imagePixels != null && !sstv.isSaving
                 )
                 // Record / Stop button
                 val playAction = {
                     when (sstv.status) {
                         SstvStatus.Idle -> onAction(RadarAction.SstvStartRecording)
                         SstvStatus.Recording -> onAction(RadarAction.SstvStopRecording)
-                    SstvStatus.Saving -> {}
                     }
                 }
                 val playColors = CardDefaults.elevatedCardColors(
@@ -237,4 +253,5 @@ internal fun SstvPage(
                 }
             }
         }
+    }
 }

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/TransceiversPage.kt

@@ -62,8 +62,10 @@ import androidx.compose.ui.unit.sp
 import com.rtbishop.look4sat.core.domain.model.SatRadio
 import com.rtbishop.look4sat.core.presentation.CardButton
 import com.rtbishop.look4sat.core.presentation.R
+import com.rtbishop.look4sat.core.presentation.formatFrequency
 import com.rtbishop.look4sat.core.presentation.infiniteMarquee
 import java.util.Locale
+import kotlin.time.Duration.Companion.milliseconds
 
 @Composable
 fun TransceiversPage(
@@ -82,7 +84,7 @@ fun TransceiversPage(
             if (selectedUuid != null) {
                 val index = transceivers.indexOfFirst { it.uuid == selectedUuid }
                 if (index >= 0) {
-                    kotlinx.coroutines.delay(300)
+                    kotlinx.coroutines.delay(300.milliseconds)
                     listState.animateScrollToItem(index)
                 }
             }
@@ -325,7 +327,7 @@ private fun ExpandedRadioControl(
                         color = MaterialTheme.colorScheme.onSurfaceVariant
                     )
                     Text(
-                        text = "${RadarViewModel.formatFrequency(radioControl.txBaseFrequencyHz)} MHz",
+                        text = "${formatFrequency(radioControl.txBaseFrequencyHz)} MHz",
                         fontSize = 18.sp,
                         fontWeight = FontWeight.Bold,
                         color = MaterialTheme.colorScheme.primary
@@ -335,7 +337,7 @@ private fun ExpandedRadioControl(
                 val upHigh = radio.uplinkHigh
                 if (upLow != null && upHigh != null && upLow != upHigh) {
                     Text(
-                        text = "(${RadarViewModel.formatFrequency(upLow)} – ${RadarViewModel.formatFrequency(upHigh)})",
+                        text = "(${formatFrequency(upLow)} – ${formatFrequency(upHigh)})",
                         fontSize = 12.sp,
                         color = MaterialTheme.colorScheme.onSurfaceVariant
                     )