MHz feed is removed from an operating demod causing AFC to lock out of range. It may
require up to a minute for lockup when the 70 MHz baseband feed is restored.
ALARM RELAY (J-1)
NO and NC contacts are available to drive external customer
equipment. The alarm relay is a miniature type (rated at 1 amp AC max) and is
intended to drive control type circuits only.
AUDIO OUTPUTS:
Both balanced and unbalanced outputs are provided. Balanced
outputs are 600 ohms with a 300 ohm source termination in each leg. The unbalanced
output is tapped off of one of the "hot" balanced terminals with an additional 300 ohms
in series to the output phono jack.
The factory meter calibration is made to the balanced output with a 600 ohm load. If
only the unbalanced output is used into 600 ohms, the signal will be 6 dB down. If the
600 ohm balanced output is used for program purposes and the unbalanced output is
used for monitoring, the unbalanced load should be Hi-Z to preclude unbalancing the
program output.
METER CALIBRATION:
(see Fig. 1)
Two factory calibrations are provided for audio
output; 0 dBm and +8. The 700 is shipped in the zero mode. To change to the +8
mode, remove the top cover of the receiver and locate the 3-pin header J 10. Move
the shorting plug from pins 2 and 3 over to pins 1 and 2.
If a level other than +8 or 0 is desired, change the output level of the receiver to the
level desired, using the front panel level adjustment. Note meter calibration pots VR5
and VR6 at each end of the header. Each pot sets the calibration of the respective
end of the header pins. These pots can be adjusted to calibrate the meter to a
customer defined value in either or both positions.
FREQUENCY SEARCH (and disable of same):
Whenever the audio noise level
becomes high, a noise-sensing squelch circuit is activated. In addition to muting the
audio and causing the alarm relay to close, the receiver AFC is disabled and replaced
by a variable tuning voltage. This voltage scans frequencies to 50 kHz below and
above the specified SCPC carrier frequency, thus compensating for LNB
downconverters which might be off frequency.
This feature can be disabled by removing the jumper on header J2 on the receiver
board (see Fig.1).
AUDIO PROCESSOR BOARDS
are the baby boards mounted in a vertical direction on
the edge of the receiver cards. Companding schemes and adjustments are to the
customer's specification and are not field adjustable.
Deemphasis time
is alterable with jumper placement. Instructions for settings from 0
to 100 microsecond time are etched on the top of the boards.
System Operation MA700SYS.SAM
SECTION 42
