diff --git a/app/src/main/java/xdsopl/robot36/HFFax.java b/app/src/main/java/xdsopl/robot36/HFFax.java
new file mode 100644
index 0000000..95f1f61
--- /dev/null
+++ b/app/src/main/java/xdsopl/robot36/HFFax.java
@@ -0,0 +1,89 @@
+/*
+Raw decoder
+
+Copyright 2024 Ahmet Inan <xdsopl@gmail.com>
+*/
+
+package xdsopl.robot36;
+
+public class HFFax extends BaseMode {
+	private final ExponentialMovingAverage lowPassFilter;
+	private final int smallPictureMaxSamples;
+	private final int mediumPictureMaxSamples;
+	private final String name;
+
+	HFFax(String name, int sampleRate) {
+		this.name = name;
+		smallPictureMaxSamples = (int) Math.round(0.125 * sampleRate);
+		mediumPictureMaxSamples = (int) Math.round(0.175 * sampleRate);
+		lowPassFilter = new ExponentialMovingAverage();
+	}
+
+	private float freqToLevel(float frequency, float offset) {
+		return 0.5f * (frequency - offset + 1.f);
+	}
+
+	@Override
+	public String getName() {
+		return name;
+	}
+
+	@Override
+	public int getVISCode() {
+		return -1;
+	}
+
+	@Override
+	public int getWidth() {
+		return -1;
+	}
+
+	@Override
+	public int getHeight() {
+		return -1;
+	}
+
+	@Override
+	public int getFirstPixelSampleIndex() {
+		return 0;
+	}
+
+	@Override
+	public int getFirstSyncPulseIndex() {
+		return -1;
+	}
+
+	@Override
+	public int getScanLineSamples() {
+		return -1;
+	}
+
+	@Override
+	public void resetState() {
+	}
+
+	@Override
+	public boolean decodeScanLine(PixelBuffer pixelBuffer, float[] scratchBuffer, float[] scanLineBuffer, int scopeBufferWidth, int syncPulseIndex, int scanLineSamples, float frequencyOffset) {
+		if (syncPulseIndex < 0 || syncPulseIndex + scanLineSamples > scanLineBuffer.length)
+			return false;
+		int horizontalPixels = scopeBufferWidth;
+		if (scanLineSamples < smallPictureMaxSamples)
+			horizontalPixels /= 2;
+		if (scanLineSamples < mediumPictureMaxSamples)
+			horizontalPixels /= 2;
+		lowPassFilter.cutoff(horizontalPixels, 2 * scanLineSamples, 2);
+		lowPassFilter.reset();
+		for (int i = 0; i < scanLineSamples; ++i)
+			scratchBuffer[i] = lowPassFilter.avg(scanLineBuffer[syncPulseIndex + i]);
+		lowPassFilter.reset();
+		for (int i = scanLineSamples - 1; i >= 0; --i)
+			scratchBuffer[i] = freqToLevel(lowPassFilter.avg(scratchBuffer[i]), frequencyOffset);
+		for (int i = 0; i < horizontalPixels; ++i) {
+			int position = (i * scanLineSamples) / horizontalPixels;
+			pixelBuffer.pixels[i] = ColorConverter.GRAY(scratchBuffer[position]);
+		}
+		pixelBuffer.width = horizontalPixels;
+		pixelBuffer.height = 1;
+		return true;
+	}
+}