J10 is the LNB (or block converter) connector. Besides providing the input signal to the 700, it provides 18 volt DC power to the LNB. This power output is protected against short circuit with a "crowbar" circuit that shuts down power in the event of a
momentary flow of excess current. Once a short has occurred, it may be necessary to completely open the LNB cable feed, or momentarily disconnect primary power before the crowbar circuit will permit resumption of DC.
The 18 VDC output for the LNB is diode protected, so multiple 700 receivers can be connected to a common LNB via L band splitters without concern. If it becomes necessary to remove the DC voltage from the coax, the jumper wire closest to the back of the tuner, looping down to the circuit board can be clipped. (see Fig. 1)
If multiple receivers are connected to an LNB, the display can indicate LNB Open on any receiver that is not furnishing enough current to extinguish the LNBO warning. -This condition will NOT activate the alarm relay.
70 MHz IF loops are made with RG59 "F" jumpers. A two channel receiver requires a jumper from J9-IF OUT to J4-IF IN. J5-IF OUT is the 70 meg source for external
devices. NOTE: As the squelch system runs on noise, the squelch will not operate if the 70
System Operation MA700SYS.SAM
SECTION 41
System Operation and Customization
The 700 Series SCPC system can be assembled in a
large variety of configurations to meet specific
requirements.
COMPONENTS to make up a 700 system consist of the following:
1:Basic chassis/case which contains power supply, microcomputer control, and a
complete front panel. See "700 Front Panel Operation" for control and display details.
2:A receiver card (CARRIER 1) for the #1 SCPC carrier, which also contains the L band transponder tuner. Optionally, the CARRIER 1 card can be supplied without L band reception. In this configuration, the system functions as a 70 MHz receiver
3:An optional receiver card (CARRIER 2) for the #2 SCPC carrier. This card receives a 70MHz IF signal from the Carrier 1 card. -The Carrier 2 card has an IF buffer so that the 70 MHZ IF is available to loop to other demodulators, if needed.
4:Audio processor "baby boards" for the receiver cards. These contain companding circuits (3:1 or 2:1 typical) and deemphasis, if used.
COAX CONNECTIONS and their functions -back panel (see Fig.2) :
