Stereo Tool

True, stereo tool has steep enough protection, you can see it in mpx spectrum. 16,2 kHz is good and sounds much better than 15 kHz.

WOW, stop for a moment
Frequencies above 14 000 .. are not bring that much "information".. So above 15 000 ( which is the standart ) is not even require .
But for the filter , yeah it`s a kind of "vertical" cut ! down to -90db and to pilot signal is about -110 -115 db .
Don`t forget that in the receiver we have lowpass filter. And no more than -60 - 65 db SNR. in the best receivers it can touch -70db.
Yes it`s true that transmitter phase noise and modulation noise is important too.

There's plenty of info above 14 kHz... Set the lowpass filter to 14 kHz and you'll hear the difference! Children can hear frequencies above 20 kHz even - and they are also listeners!

If somebody don't hear difference between LPF 14kHz and 16,2kHz so i think it's no good
For my perception and trade off between sound quality and useful FM bandwidth with limited deviation 15,8kHz is optimum.
SSB may give more space between RDS subcarrier, but not to pilot tone

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Urban Junglist

I`m talking about FM broadcasting , not for normal listening . In normal listening there is no lowpass at 15 may be lower . In receiver there is lowpass. That is why i say that above 15000 for FM is completely unnecessary . Let alone above 15khz... We all know that pilot signal must be completely clean from any modulation signal, RDS too.


Imagine the Analog filtering Stereos ? IS they that steep like ST? NO. There is even lower lowpass frequency limit to achieve a good pilot cross-signal . Not every bandpass is like ST bandpass .That is why there is a standart for FM . 30HZ-15000Hz for high quality broadcasting .

But if they put the pilot at 23khz and RDS at 70khz or 72 , the picture will be like this : Lowpass at 20 000 hz , pilot at 23 000hz, L-R to 66 000 hz and RDS at 70Khz or 72 It`s more like CD quality , right ?

I'm talking about FM broadcast too.
I don't use above 16kHz but because limiting highs in e.g. ST and demphasis in tuner gives very low levels and very low dynamic above 16kHz, so i'ts not recommended to use it.
I made many test and for me 15,8kHz is good maximum.

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Urban Junglist

Most FM receivers contain 15 khz lowpass, but modern ones have 16 khz (mobile phones, stereos, car radios, etc.)
It's OK to keep the lowpass at 16 khz, if you have very good sound card and high-quality transmitting equipment. This will increase the quality of the audio, especially on the receivers, stated above. Make sure you also have a highpass filter set at 30 hz minimum, as, sometimes, frequencies below cause interference.

True about lowpass in "tuners', but shape of LPF is NOT steep.. So on any tuner you will have decent difference between 15 and 16kHz steep LPF.

Many FM tuners have only 19kHz trap, and 3dB loss begins at ~17-18kHz.

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Urban Junglist

Difference between output with BETA048 and BETA049 with new "Band Coupling" filter, set to 40% (higher values are probably better, don't know yet).

www.sendspace.com/file/t572za