Software Defined Radio
DiRaGen 30 USB
AMSS
+++
AMSS - A system for adding informations to an analog AM modulated broadcast signal
AMSS (Amplitude Modulation Signalling System) is a system for transporting text informations via amplitude modulated broadcast transmitters within the long-,medium- and shortwave bands.
A comparable system for frequency modulated signals is RDS - Radio Data System for FM transmitters.
AMSS informations can be received with a suitable DRM receiver like e.g. our DRB 30 or 32 in combimnation with corresponing decoder software like DEREAM, SoDiRa or G8JCF.
In the following we will regard the transmission technique. The combination of SPARK modulator software and DiRaGen 30 USB is used to generate an AMSS signal.
+++
Chosen SPARK settings:
Audio Bandwidth: 5000Hz ( 5KHz)
Mod. Degree: 1.00 (100%)
AM-Mode: Double SidebandCarrier Suppression: OFF
Enable AMSS: ON
Music modulation via chosen MP3 playlist
+++
Transmission & performance tests
Output frequency is 10MHz.
The PC-controlled shortwave receiver DRB 32 in combination with the DRM decoder software DREAM is used for reception of the test signal.
For best performance the internal AGC function of DREAM should be deactivated (AGC off) because the DRB 32 is already equipped with an integrated AGC which is optimized for data reception.
First a input level of -20dBm is fed directly into the DRB 32 for testing the complete system at maximum input level range just before saturation occours:
An SNR (Signal-Noise- Ratio) of more than 60dB is obtained and AMSS inforations are decoded without problems. erreicht und AMSS problemlos dekodiert.
Then we insert an additional switchable step attenuator and attenuate the input signal stepwise until AMSS reception shows first signs of interruptions.
This point is achieved at an input level below -110dBm:
Finally we want to determine the threshold for error-free AMSS reception. The signal quality degrades rapidly below -115dBm with a corresponding SNR of 15dB.
Final result is a dynamic range of higher than 80dB for AMSS reception which represents an excellent value.
