Complex transmissions often consist of multiple distinct frequencies or data streams combined together. A subsignal represents one of these isolated streams, such as the color burst in analog video or a specific telemetry channel riding on a main carrier. Isolating a subsignal requires targeted filtering or demodulation to extract its specific data without interference from the rest of the composite waveform.
Heard on the job
The spectrum analyzer shows the main carrier is clean, but the telemetry subsignal is getting buried in the noise floor.