FM

kspv schrieb:

Whether the sound we hear in case of stereo-FM transmission in India (Radio City, Radio Mirchi etc.) is a full frequency range one (20 Hz-20KHz) ? Why I am asking this question, is that I know the Worldspace is not full frequency range sound, being MP3 compressed and pruned for band-width optimization.

KSPV: why is this question relevant?
let's say that FM in India is not full bandwidth. What are you going to do about it?
Stop listening to radio?
Somehow lobby in Parliament that it should be full bandwidth 'cuz audiophiles like you prefer full bandwidth FM sound?
Build a freq expander box to make the FM transmission full bandwidth for your listening pleasure?

The info from Worldspace is probably written/documented on their website hence you know. I *bet* that you cannot tell from listening to the broadcast!

Most importantly: are you missing the frequency extremes?
The very fact that you have asked the question implies that you cannot tell from listening!
So, it probably does not matter!
So, don't get so hung up about this & just tune in & listen & enjoy.
If it bothers you so much, get into DXing!

Dxing sad the Shortwave is almost dead

My question is of academic interest. Besides, the curiosity arose because I could sense a difference, and felt that the FM transmissions are voiced in a particular way. I just wanted to know whether my guess is correct (not because I could approach the Indian Parliament, and do something about the 'audiophile' part of it). My observation is that if I wanted to approximate to the kind of sound I get when I press the 'CD-direct' button on my amplifier while using my CD player as the source, it required ample use of the tone controls of my amplifier in case of FM radio.

Secondly, Worldspace actually claims 'CD quality' sound in their brochures, and that is what most people believe it to be. On the contrary, from my listening experience, I felt that it may not be so. In the end, I could infact confirm my hunch that it is not so, by going into the details of satellite stereo transmission. The next time you feel that one can not tell the difference between Worldspace transmission and the CD-sound, all you have to do is to switch on your subwoofer during the Worldspace session, and observe whether it produces any sound.

Whether the sound we hear in case of stereo-FM transmission in India (Radio City, Radio Mirchi etc.) is a full frequency range one (20 Hz-20KHz) ? Why I am asking this question, is that I know the Worldspace is not full frequency range sound, being MP3 compressed and pruned for band-width optimization.

Hi kspv,

An interesting question, that I feel deserves further ventilation

A. The little known fact is that No FM Stereo radio transmissions extend to 20 KHz.

FM Radio transmissions first commenced in Single Channel Only ( Mono ).

My knowledge on this is a little rusty, (and the 'net connection by Sify is CRAWLING today, so I cant research and be 100% sure.) but single channel FM Radio transmissions extended upto 14 KHz or 15 KHz only. This too was a 'vast' improvement over AM radio which extend to 8KHz.

When stereo FM transmissions commenced, they had to be 'backward compatible' i.e. all earlier, non stereo receivers should continue to receive FM radio. Hence the FM Stereo radio transmissions consisted of 2 signals transmitted simultaneously:

1. A mono signal, i.e. a mix or sum of the left + right channels. (L+R channels)

2. A 19KHz tone that was modulated to carry the small amount of 'difference" info: the Difference between the Left & Right Channels (L-R).

Hence the stereo receiver received 1&2 while the old mono FM receivers received only 1, and simple did not even know of the existence of 2.

The Stereo FM receiver, recovers the L & R signals by adding and subtracting 1 & 2. viz:

(L+R) + (L-R) = 2 L ( i.e. 2x Left channel, a simple resistor will divide the signal by half to get just L or the Left channel )

(L+R) - (L-R) = 2R.

The 19 KHz stereo carrier tone is removed using a low pass filter. ( this was in the days before the extremely sharp digital filters. )

Hence FM stereo supports only 17 KHz ( or is it 18KHz.... my rusty knowledge ).

B. FM radio stations the world over ( with the exception of a few audiophile FM stations) typically Compress the sound, so that it has a perceived Louder sound. The sound is also 'equalised' to make it sound "better" on ther basic FM receivers used by most listeners. The equalisation & compression also provides better perceived sound quality in fringe areas and noisy environments like cars.

So much for FM radio.

However, all that said, even with its 17KHz bandwidth, FM Radio transmissions when done well, can approach Hi Fi quality pretty well.


WORLDSPACE:
This is a satellite based service, and bandwidth on satellites is spares or Very Expensive. World space uses its own satellite, and squeezes in as many channels as possible. As you have correctly quoted -- they claim "NEAR CD" quality.

How NEAR ? and "Near ENOUGH" for whom ?

http://transmitters.tripod.com/stereo.htm

well written article about stereo FM that may be intersting to the valuable info provided by Mr. Amp Nut

get into DXing!

DXing is hardly Hi Fi, infact me thinks its not even fi !



Also,
Thanks for the pointer, ani on that article.

Wow, I got my answer!!