From: "Holger Waechtler" <[EMAIL PROTECTED]> > no, e.g. the L64781 and the tda10021 report no inversion. Some revisions > of the TT DVB-C card too. The reason for the inversion is probably that > the hardware designer swapped the I/Q wires between tuner and demodulator.
AFAIK, there is no such thing as "I/Q wires", only a (typically differential) IF signal between the tuner and the demodulator. From my understanding, the spectral inversion is generated in the tuner - You _add_ the IF centre frequency to the desired target frequency to calculate the PLL frequency. If I understand the downconversion process correctly, the PLL frequency is _subtracted_ from the input frequency: input target frequency - (target frequency + IF) = -IF Thus, the target frequency ends up _spectrally inverted_ at the IF, and the demodulator has to perform a spectral inversion to recover the original signal. Or is my understanding completely wrong...? Regards, -- Robert Schlabbach e-mail: [EMAIL PROTECTED] Berlin, Germany -- Info: To unsubscribe send a mail to [EMAIL PROTECTED] with "unsubscribe linux-dvb" as subject.
