RDS Encoder

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• Adjustable phase shift
• Internal or automatic reference set switch

Supply voltage: 5 V
Supply current: 12 mA
Max. 19 kHz input sensitivity: 10 mV p-p for square, 100 mV rms for sine
Input impedance: >100 kOhm
57 kHz phase shift adjust: 0-90 degrees

Input - 19 kHz reference input connector
1: input
2: ground

Input level - 19 kHz input sensitivity adjust (trimmer 2)

Phase - Phase shift adjust (trimmer 3)

57 kHz - Free running oscillator 57 kHz set (trimmer 4)

Int./auto - Internal or automatic reference set switch
Open: internal 57 kHz reference
Short: automatic reference set (automatic pilot tone synchronisation if 19 kHz pilot tone reference is present)

LED - In-lock indicator

Encoder - Interface to the RDS encoder
1: +5V power supply
2: input for internal RDS encoder 57 kHz reference
3: 57 kHz output
4: ground

1. Adjust right RDS signal output level.
2. Set the reference switch to automatic.
3. With input shorted set 57 kHz on pin 5 of 74HC03 using corresponding trimmer. Alternativelly, if you don't have a counter, set almost maximum 19 kHz input sensitivity by trimmer 2. Then fetch a 19 kHz signal to the 19 kHz input and set the trimmer 4 to the position where the LED is lighting.
4. Fetch 19 kHz signal from a stereo encoder to the 19 kHz input and adjust right input sensitivity (start on zero position) - the LED 2 must light for all positions of trimmer 3.
5. Adjust right phase shift (0 or 90 degrees phase shift between 19 kHz pilot tone and 57 kHz RDS subcarrier, measured on transmitter input). This adjustment is impossible without an oscilloscope. Never mind, if you don't have this equipment. Simply set the corresponding trimmer to the position where you think the signal is the best. Be sure that it's difficult to recognize any differences...
6. If needed, repeat from step 4.

Simply connect the pins with the same number on 4-pin interfaces. The connection should be as short as possible. Power supply of the circuit is also provided from the RDS encoder unit through this connection.

If the stereo encoder has a 19 kHz output, it's easy. Simply fetch this signal to the pilot lock circuit using thin shielded cable.
In some cases it's necessary to fetch out the 19 kHz pilot signal from stereo encoder or stereo transmitter if the equipment doesn't have this output. This is always possible, but there exist many kinds of used circuits. It's difficult to describe any general way.
For example, the BA1404 circuit has 19 kHz output on pin 13, which can be connected directly to the PLL circuit. See following picture:

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