Junger Audio d07 - Digital Transmission Processor - Manual (Page 65)

B 7 FM-Transmission d07
Pre-Emphasis
Increase of high frequencies to enhance the signal to noise ratio for FM
transmission equals to a time constant of a high pass filter of 50
µ
s in Europe and
75
µ
s in America. It will be laterally reversed at the receiver end. This value does
not comply with todays spectrum of audio signals. But it is not possible to change it
because of the innumerable receivers. Therefore modern audio signals may easily
over drive an FM transmitter, causing nasty interferences.
Adaptive Pre-Emphasis
Function of the d07 that makes it possible to dynamically accommodate the level of
an audio signal to the high frequency boost of an FM transmitter. The effect is that
over driving by high frequency signal components in critical programs will be
avoided (s.a. pre-emphasis).
MPX-Spektrum
38 23 19 15 53
Differential signal
(L - R) = S
Auxiliary carrier
- pilot ton -
Illustration of base band spectrum of a MPX signals
Frequenz
in kHz
Compatible monaural signal
(L + R) = M
Spectrum of
MPX signals
Double sideband
suppressed carrier
power of the M - signal
proportional to the square of the
amplitude of the M-signal
P
M
~ M 2
power of the (-S) - signal
proportional to the square of the
amplitude of the (-S) - signal
P
-S
~ (-S) 2
57 76
RDS
(Radio Data System)
auxillary carrier
DARC
(DAta Radio Channel)
auxcillary carrier
power of the (+S) - signal
proportional to the square of the
amplitude of the (+S) - signal
P
-S
~ (+S) 2
MPX-power
Overall power of the Multiplex signal from the sum of components of the MPX
spectrum :
Monaural signal (M=L+R)/2 30Hz to 15kHz base band
Auxiliary carrier 19kHz approx 9% of overall power
Double side band suppressed 23kHz to 38kHz lower side band
carrier modulation (S=L-R)/2 38kHz to 53kHz upper side band
RDS signal
DARC signal