Displaying RDS information

This is a duplication of the work that Nick has done (see link), with the exception that the radio used here (a Ford 5000RDS) has an SGS-Thomson TDA7330 rds decoder chip rather than the Philips SAA6579. However, the same outputs (RDDA, RDCL and Quality) are available from either device

[The TDA7330 may actually be a TDA7331, which is an improved version. Ford, unfortunately, seem to insist on having their suppliers mark their ICs with non standard part numbers].

The pics below show the radio, the TDA7330 (bottm rh corner, below the ribbon cable) and the spectrum of a typical transmitted signal, which is a composite of L+R, pilot tone, L-R [double sideband suppressed carrier], and RDS [again, double sideband suppressed carrier].

The audio spectrum (10KHz/horizontal division, 10dB/vertical division) shows just how low level the rds modulation is, being some 30dB down on the L+R audio level.

Invalidation of radio warranty

This was achieved by wiring to the reverse side of the main pcb....

The RDDA, RDCL and Quality connections all exist as plated through holes from the top side. Not only that, but these three points also have test pads tracked, which is where the added wires where actually soldered. A 25way D connector was internally fitted as shown below. The pin numbering mimicks those of the 20 pin TDA7330 chip, for clarity.


The following circuit (again lifted straight from Nicks web page) uses a 16F84 PIC (with Nicks source code)to interface with the PC, running - you guessed it - Nicks RDS monitor software.

To be finished...