Tagged: Subsidiary communications authority

Using an SDR# Plugin to Tune into a Broadcast FM SCA Subcarrier (Radio Reading Service for the Blind)

Thank you to Double A again for submitting a new video where he shows how to use a new SDR# plugin called "SCATuner" to listen to an SCA audio subcarrier embedded within a broadcast FM signal.

SCA short for Subsidiary communications authority, is a separate audio channel hidden within a broadcast FM signal. SCA is typically used for niche radio programs, elevator music, music for doctors offices, and niche services such as reading for the visually impaired. In the past you needed a special hardware SCA radio to receive these channels, however receiving these channels with an SDR is relatively simple. Not all broadcast FM stations will have an SCA service, but the video shown below explains how to find one.

In previous posts Double A and others have shown how to receive these SCA Subcarriers using two instances of SDR#. However, this new plugin makes the task much simpler one click job.

Double A's video goes over how to install and use the plugin, explains SCA and demonstrates it in action decoding a radio reading service for the blind.

SDR# Plugin for Tuning an FM SCA Subcarrier (Radio Reading Service for the Blind) (with RTL-SDR USB)

Receiving the ‘Hidden’ Broadcast FM SCA Audio Subcarrier with an RTL-SDR and SDR#

Broadcast FM channels can often contain additional subcarriers hidden within the bandwidth. A common subcarrier is Radio Data System (RDS), and this is what provides song and radio station text information to your radio.

Another less commonly seen subcarrier is the Subsidiary communications authority (SCA), which is a separate audio channel hidden within the broadcast FM signal. SCA is typically used for niche radio programs, elevator music, music for doctors offices, and niche services such as reading for the visually impaired. In the past you needed a special hardware SCA radio to receive these channels, however receiving these channels with an SDR is relatively simple. Not all broadcast FM stations will have an SCA service, but the video shown below explains how to find one.

Over on YouTube channel Double A has uploaded a video showing how to decode these SCA subcarriers using an RTL-SDR, two SDR# instances and the MPX Output plugin. The idea to to use a virtual audio cable to pipe the FM Multiplex (MPX) audio output from one instance of SDR# to another. In the second SDR# instance you can then directly tune into the SCA channel. In his video he also explores the FM MPX spectrum, showing the different components, and also how to install and use RDS Spy for decoding RDS.

Tuning an FM Audio Subcarrier (SCA) & Decoding RDS Data with RTL-SDR USB