ALF-RDS (Accurate positioning by Low Frequencies) is a German system for the transmission of DGPS information on low frequencies (in this case 123, 7 kHz). Data is transmitted in RDS format. RDS (Radio Data System) is a one-way data transmission system used by FM broadcasters worldwide to broadcast program, time and traffic information on a 57 kHz BPSK DSB sub carrier with suppressed carrier and a bit rate of 1187.5 bps. In the case of ALF-RDS, the transmission is made in SSB with a decreased level pilot carrier to reduce bandwidth.
|
Parameter |
Value |
|
Frequency range |
HF |
|
Operation modes |
Broadcast FEC |
|
Modulation |
BPSK |
|
Symbol rate |
1187.5 Bd |
|
Receiver settings |
DATA, CW, LSB or USB |
|
Input format(s) |
AF, IF |
The basic RDS data unit is a group which consists of four blocks, each having 16 data bits and 10 error detection and correction bits. Groups are divided into type A and B, each containing 16 different groups.
In the upper window, a Display Mode can be selected. The default display mode is All Blocks, which displays the information of each block. Binary will display the contents of a group in binary format.
In the lower window, other information like flags, time, program information and transmitted text is displayed.