junger d07 Operation Manual page 81

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 50μs in Europe and
75μs 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
Spectrum of
MPX signals
Compatible monaural signal
(L + R) = M
power of the M - signal
proportional to the square of the
amplitude of the M-signal
P ~ M 2
M
MPX-power
Overall power of the Multiplex signal from the sum of components of the MPX
spectrum :
Monaural signal (M=L+R)/2
Auxiliary carrier
Double side band suppressed 23kHz to
carrier modulation
RDS signal
DARC signal
Auxiliary carrier
- pilot ton -
power of the (-S) - signal
proportional to the square of the
amplitude of the (-S) - signal
P ~ (-S) 2
-S
15 19 23
Illustration of base band spectrum of a MPX signals
30Hz to
19kHz
(S=L-R)/2 38kHz to
Differential signal
(L - R) = S
Double sideband
suppressed carrier
power of the (+S) - signal
proportional to the square of the
amplitude of the (+S) - signal
P ~ (+S)
2
-S
38
15kHz base band
approx 9% of overall power
38kHz lower side band
53kHz upper side band
RDS
(Radio Data System)
auxillary carrier
DARC
(DAta Radio Channel)
auxcillary carrier
53 57 76
B 7 FM-Transmission d07
Frequenz
in kHz