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sound card + half-wave rectifier

Ottawa Dave wrote:

What does RDS Spy look for when receiving analog input from a half-wave rectifier + RDS encoder? (Section 3.3 in RDS Spy manual.) My guess is that the 19 kHz pilot mixes with the 57 kHz RDS data in the diode, to produce many mixing products. Is RDS Spy looking for the RDS signal shifted to baseband by the 3rd harmonic of the pilot? For those of us with basic 48 ks/s soundcards, it may be possible to use a second computer running gnuradio companion with an appropriate flowgraph to implement an FM demodulator + RDS signal downconverter. There already exists gr-rds for the RTL-SDR USB dongle but I suspect the performance is inferior to RDS Spy. One could create a flowgraph customized to a variety of radio solutions, e.g. a tap-off from the IF of a high quality FM receiver.

admin wrote:

This RDS source is obsolete as it is fully replaced by the 192 kHz sound card source. The diode really works as a rectifier, not a mixer. Pilot is not allowed in the input signal. Using this source the RDS Spy can decode RDS directly from any RDS encoder output, without need of any special hardware.

Keroronsk wrote:

Hello. In the manual there is thresholds levels (so it's possible to tune thresholds in program options). But in real software this window looks different. I've tried 1.02 and 1.00, and it was same. How I can if my rectified RDS level is OK?
Here is screen shot:

http://dl2.joxi.net/drive/0000/1576/1576/150325/5163e7d6ac.jpg