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View Full Version : Whats up with this Spectral?


acov
2007-05-05, 05:21 PM
I received a Pantera show on CDR from someone...

dont worry i wont upload it here but i wanted to know to account for the seemingly weird spectral but decent frequency?

would it still be considered lossless because of the frequ?

guygee
2007-05-06, 07:50 AM
I was trying to figure out the significance of the spike at 19KHz. I was wondering if the way that stereo signals transmitted by FM might have something to do with it:

A stereo FM broadcast consists two signals are mixed in such a way that two output signals are produced, one is (L + R) and the other is (L - R). In turn, these two signals are processed to produce FM signals, one at the carrier frequency and the other at the carrier frequency plus 19kHz, that are transmitted from the station. When you tune to the station, de-modulation in your radio receiver recovers the two signals, (L + R) and (L - R). To get the individual L and R channels these two signals are added to produce:

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

i.e., the original left signal, and subtracted to produce:

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

i.e., the original right signal.

Could the 19KHz spike be an artifact of some problem with the reproduction of an FM stereo signal? I'm really not sure if I am on the right track...I would be interested in anybody else's thoughts on this.

AAR.oner
2007-05-06, 08:21 AM
yep, looks to be from an FM source due to the pilot tone at 19kHz, which shows as a "stripe" on a SA and a "spike" in FA

i'll move this thread to our "Lossy or Lossless?" forum so that some of our resident experts will see it, they know far more than i on the subject

acov
2007-05-07, 01:35 AM
i guess im wondering, well not on this site, but were i to trade with someone somewhere could i legitmately advertise this as a lossless show?

Five
2007-05-10, 02:43 PM
I can hardly see anything in the sa pic... it looks like its cutting off at 10-11kHz yet there's the carrier up there which is strange. could you upload a sample to rapidshare or similar or put up some cep sa pics? see here (http://www.thetradersden.org/forums/showthread.php?t=4288) for some links.