RDS Surveyor is being developed by Christophe Jacquet, a French radio ehtusiast.
RDS Surveyor needs a source of RDS data (a bitstream at 1187.5 bit/s). One way to achieve this is to use a radio receiver USB dongle such as the RTL-SDR. Another way is to hook a classical radio set to your computer, and that is what this page describes. You need to proceed in two stages:
The PR-D1 was available from Sangean at the end of the 1990s. The service manual of the PR-D1 is now available online.
The PR-D1 has its own RDS decoder chip, an SAA6579 from Philips Semiconductors (now NXP). I suppose that one could tap the RDS bitstream directly from this chip, but I found easier and safer to use the multiplex output instead.
The first thing to do is to remove the back cover of the radio set. First remove the two screws at the back (do not remove the antenna screw!). After that, only “clips” hold the back cover in place. Look at the service manual, press inwards at the places where clips are located. Be careful, the clips are fragile, and I personaly broke a few of them (which is not so much of an issue, the back cover still remains in place without any problems).
After removing the back cover, you have he main circuit board in from of you. At the bottom left-hand corner, there is a wide horizontal connector, which contains the two pins of interest for us: the ground and the multiplex signal.
Solder wires to these pins, and there you go! Personaly, I used an audio shielded cable after the first test showed above, and connected it to a .1"-jack socket on the front panel to take the signal out of the radio. There is room for a jack socket at the top left-hand corner of the front panel (as seen from outside), just near the antenna connection.
My RDS demodulator uses a TDA7330 from STMicro and an optocoupler (TLP521-4). The output of the optocoupler is level-adapter to be fed into a sound card.
The optocoupler outputs are open-drain. They are connected to the medium point of a voltage divider. The sound card output is at this point, too. In this way, if the sound card's input impedance is infinite (no leak current), then the voltage is either 0 (low) or 1.5kΩ / (10kΩ + 1.5kΩ) ⨯ 5V = 0.65V. This is the right level for the line input of a sound card, that accept voltages up to 0.7V. In practice the input impedance won't be infinite, so the voltage will be lower than 0.65V, but still high enough for the decoder to work. In any case, the voltage will be between 0V and 0.65V, so the sound card should not be damaged.
My prototype on Veroboard:
This circuit works fine for me. However, if you with to use it, you do it at your own risk. I could not be held responsible of any damage caused to any person or equipment (radio set, computer, etc.).