Stereo Tool

Bug fix: When I added the improved RDS filtering in 3.52, I have also introduced a time shift in the RDS signal which may cause RDS reception on some (especially German) radios to fail. Fixed in this 3.53 version, which is available on the download page.

unlikly how are you fast
let's me test it.

edit:

ok .. tested ... 3.53, and in this car still no RDS. (sometimes there is one word)
but i just determine that half stations in area has no rds at all in this car. But i know they have.
on every other rds reciver i found, ST rds working good.
hmm. maybe this reciver is bug

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If you sometimes see one word, try Luke's advice from the 3.51 thread: Repeat every word for at least 5 seconds. I know it's slow, but I have read that some car radios don't support changing RDS text because it would distract the driver. Changing the text really slowly could help here.

i know for that.
curentlly i have 6 words at 1.5s .. but one station in area have 40 words in mesage at 1second , and it's shown on every RDS reciver i can get.
this special reciver i found in this car is not so importent if i know that the ST RDS is shown regulary on every other.
i was just mention that case.

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capture from mpx tuner (no rds because tuner is not rds capable)

Stereo Tool ON AIR !

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Hi Bojcha,


Sorry to dissapoint you but that doesn't look good at all
Where exactly did you take the audio from? Did you alter the tuner inside or just connected to the one of the Left or Right outs on the back of the tuner??
Also there should be nothing between 15KHz and the 19KHz pilot signal.
If you alter your tuner you should also be able to see your composite signal.

This one is straight from my altered Sony ST-SA5ES tuner
Terratec Areon space -> SBS FM-transmittor (100 mW) -> Tuner

I would indeed expect something like the bottom graph... Is the reception very poor?

Also, bad reception could explain part of this, but the fact that your radio doesn't support RDS does not mean that you shouldn't see it in the graph! (Assuming that you are getting an MPX signal from your receiver).

Edit: I think I know what's wrong. Your CAPTURING sound card is not capable of capturing at sample rates above 96 kHz! (It must be the sound card that is used for capturing because you mentioned that RDS does work). So in your analysis you miss everything above 48 kHz (part of the stereo info is also missing), and the card or Windows seems to use a very poor upsampling algorithm (which could explain all the noise, and the fact that there IS noise above 48 kHz even though there should be nothing there if the card doesn't capture it.)

Luc, I never knew that there are receivers that have such low noise levels! Now I understand why you were so keen on improved filtering

What sound card are you using? I'm asking because the output looks reasonably constant, although I'm still seeing some peaks that are slightly (about 10% or so?) louder than others in your image. Of course I don't know if this is caused by the output to the transmitter or by the input from the receiver... (If it's caused by the output you could try using the FM Transmitter Calibration to get rid of it, but if it's caused by the input you would in fact be making things worse.) To be certain about this you would need external (and apparently very expensive) tooling...

ohhh

i use technics ST-Z55 with mpx output .. and realtek alc1200. the output on this souncard is really 192kHz capable but i am not sure for input... and maybe i have "not so clear" reception (5km from 100w transmitter)

and that is crazily .. so low signal (=0) between 15kHz and 19kHz.

Luk what soundcard you use for transsmiter and recive?

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Hans, this is a top notch receiver that has also been modified by me
As a matter of fact if I do a compare between the output of the audiocard and the tuner there is not much difference.
The image seems to be just a bit of luck as I can see 'noise' between -85 to -80dB which is already exceptional.

My deviation is also completely off the 75KHz scale, must be around 100KHz since the IF filters were changed to do some testing.
The reason why I did this is because I don't like noise interfering when I measure stuff and this gives me a bit of extra heardroom.
If I really need to make real life measurements I will switch the receiver to 'narrow' mode which will give me the standard IF wide.

The SBS transmittor has also been modified with handpicked mosfets/capacitors making it so that I can turn the amp and hear ... nothing.
It also helps that I insert the RF-signal into the tuner 'directly' using attenuators so that there is enough snr

For audiocards I use 2 Terratec cards, one the aureon space and the other the aureon sky, BUT , both have been flashed to Audiotrak prodigy 7.1 cards which are bassicaly the same but have much better software and more options.

The not so constant output in the graph you see on my image might be caused by the fact that it is an intro of a song and

Bojcha, like Hans said your input might not be capable of 192KHz which explains the sudden cutoff at 48KHz (96KHz/2) and the fact that you are 5km's away of the transmitter is the explanation of the 'noise' that we are seeing.