Vision/Sound modulator BTM 501/1
Within the vision/sound modulator, the vision carrier (38,9 MHz) is amplitude-
modulated by the processed video signal and VSB-filtered. The audio proces-
sing, the matrixing and the modulation of the 1st sound carrier also takes place
in the vision/sound modulator. The vision sound modulator supplies the
l
IF vision carrier and
l
IF sound carrier 1.
Quarz oscillator
The oscillator in the vision sound modulator is locked to the external reference
frequency (REF).
SAW filter
Following the VSB modulation, the saw filter limits the band width, ensuring
flawless adjacent channel operation.
Sound part
The sound part contains two symmetric audio inputs with switchable input impe-
dance (600 ohm/>12 kohm).
The level can be set between 0/+6 dBm (referenced to 600 ohm) using swit-
ches on the assembly and in a range from -3 ... +3 dB on the front panel.
The substitute sound inputs are asymmetric, highly resistive and not tunable.
(Level = +6 dBm / 600 Ohm)
Preemphasis
The preemphasis (50
µ
s) can be switched off on the assembly to carry out
measurements.
Matrixing
The transmission mode (mono/stereo/2sound) is determined from the data line
in the sound2 modulator. This information is then passed to the
vision/sound modulator via the "stereo" control line.
Sound IF
The sound carrier frequencies 33,4 and 33,158 MHz are derived from the
vision carrier frequency 38,9 MHz and are frequency-modulated directly by the
matrixed audio signals.
Sound carrier lowering
The sound carrier can be lowered by 3 dB with a switch on the assembly.
Switchover to
the substitute signal
The switchover to the substitute signal occurs at the same time with the video
processor. The timing of the switchover is determined in the video processor
and this information is passed on to the vision/sound modulator via the
"MAIN/AUX" control line.
Operation
Manual
ü
PAL modulator 1 HU
2 - 7
Summary of Contents for PAL 1 HU
Page 1: ...Manual PAL modulator 1 HU version 1 2 print March 96 BH_1760E Hirschmann...
Page 4: ...Index Manual 0 4 PAL modulator 1 HU...
Page 5: ...Introduction Introduction Manual PAL modulator 1 HU 1 1...
Page 7: ...Operation Operation Manual PAL modulator 1 HU 2 1...
Page 14: ...Block diagram Vision sound modulator Operation Manual 2 8 PAL modulator 1 HU...
Page 22: ...Operation Manual 2 16 PAL modulator 1 HU...
Page 23: ...Service Service Manual PAL modulator 1 HU 3 1...
Page 27: ...Data sheets Data sheets Manual PAL modulator 1 HU 4 1...