Old Forum

Radio Data System - DSPX FM

Jim, 12.11.2009, 23:01
DSPX FM

I came back to read the posts. Above you said:
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Jan, 5.11.2009, 09:04
Re: Too low RDS signal

It was already discussed here. The DSPX SCA input cannot be used for RDS without a modification, opposite to all standard FM broadcast equipment it has too low sensitivity and cannot be adjusted. Connect the RDS encoder into the MPX path (loopthrough mode). Another way is to boost the PIRA32 RDS level above standard by changing one resistor value - more info on email.

But in the past, there was a related thread.
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Eric, 10.8.2009, 21:26
PIRA32 RDS introducing noise - Reply

We have a PIRA32 RDS and use a DSPX-FM for sound processing. The DSPX sounds great, until the PIRA is put in line. If I unplug the PIRA, I do not hear clipping/overmodulation. If I drop the stereo encoding on the DSPX, I do not hear clipping/overmodulation. But, if I have the PIRA RDS injection above the lowest level setting, I get clipping/overmodulation noise in the transmission.

My exciter will not handle a separate feed for RDS. How can I use the PIRA without creating crackles, clicks and other noise?
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Thanks!Jan, 11.8.2009, 08:52
Re: PIRA32 RDS introducing noise - Reply

The PIRA32 is used with DPSX without any problems (although the SCA injection in the DSPX unit could be higher than 10% or adjustable). RDS output to SCA, pilot to RDS input. The mistake you probably made is that you left the JP2 (MPX loopthrough) jumper closed so pilot goes twice to MPX. It's not only the PIRA32 related, this applies generally to all RDS encoders.
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So, my question is, how should a DSPX be configured with the Pira. Using the MPX method, the Pira basically picks off the stereo signal, then modifies it to including the RDS data, right? Would this best be handled by the Soundprocessor/stereo generator (DSPX)?

If that is the case, would you mind posting the mod for the Pira?

Jan, 13.11.2009, 19:35
Re: DSPX FM

Dear Sir, any questions related to the DSPX configuration must be addressed to its vendor. From the information that is available the DSPX has about 20 dB attenuation on the SCA input without any possibility of adjust. The reason is unknown for me. It makes the signal level problems when connecting most of RDS encoders and other accessories that use baseband above 53 kHz. The SCA input of the DSPX is probably designed for a specific device.
In the loopthrough connection mode (we can designate it as compatibility mode) the signal level problem does not exist since no RDS signal is handled by the stereo generator and the RDS is injected behind.

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