IQ trim - portapack-mayhem/mayhem-firmware GitHub Wiki

SCR_0072

IQ Trim allows you to trim "radio silence" from the beginning and end of a C16 or C8 capture file.

UI Components

Field Description
Capture File Tap to open a .C16 or .C8 file from the CAPTURES/ folder.
IQ Display Shows the signal power across 240 buckets. The green line marks the Start position, the red line marks the End position.
Start Starting sample of the trim region. Adjustable manually. Step size scales with file length.
End Ending sample of the trim region. Adjustable manually. Step size scales with file length.
Samples Total number of samples in the capture file.
Max Pwr Power (complex magnitude) of the strongest sample in the capture file, after amplification. Shown in red if the amplification setting would cause clipping.
Cutoff Signal-to-noise cutoff as a percentage of Max Pwr (1–100%). Default: 7%. Used to automatically determine the Start/End trim points.
Amplify Amplification factor applied to the trimmed file (1–9×). Default: 1× (no amplification). Useful if the captured signal was weak.
Trim Applies the trim (and amplification) to the file. Overwrites the file in place — no backup is made.

Trimming Capture Files

  1. Open a capture file by tapping the file path field. You should see the signal power displayed in the IQ Display.
    • If the display shows no visible block, the captured signal was too weak for the tool to detect automatically.
  2. Either adjust Cutoff % to automatically set Start/End, or set Start and End manually.
  3. Optionally increase Amplify if the signal was weak. Watch the Max Pwr field — it turns red if clipping would occur.
  4. Press Trim. The file will be edited in place.

[!WARNING] Trim overwrites the original file without making a backup. Use the File-manager to make a copy first if you want to preserve the original.

Splitting Capture Files

Capture files can be split into multiple files by combining File Manager and IQ Trim:

  1. Use File-manager to make copies of the original capture file.
  2. Open each copy in IQ Trim and trim to the desired Start/End range.
  3. The resulting files can be trimmed further if needed.