No at least not for cryptographic steganography  I should say first that steganography is a much slipperier subject than cryptography  its harder to specify and analyze  But a spreadspectrum signal need not be any harder to detect than a narrowspectrum  A signal that is transmitted at a very low bitrate may be difficult to detect but even this is not necessarily true  In steganography the message is normally hidden inside another message  The study of analog technical ways to transmit signals secretly is not really within the purview of steganography  it includes tricks like lineofsight infrared lasers transmissions as short high data rate bursts and other esoteric tricks