Larcan FM-250, Техническое руководство

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FM-250 FM BROADCASTING EXCITER
Issue Date: 21 Jan 2003
output power in the Exciter with respect to the Control voltage (The ALC Output is used to
control the Gain of the RF PA via the Mosfet gate voltage). This arrangement controls the
power output of the RF PA and the other inputs to the circuit are only there for protection
purposes, by reducing the output power during fault conditions.
•
LK1 is used to insert protection from High reflected power . (option)
•
LK2 is used to change the standard Temperature back off level from 55
°°
C to 60
°°
C .
•
LK3 is used to insert protection from High RF PA Current . (option)
g) Telemetry connection (see circuit diagram)
The Telemetry outputs at PL7 provide voltage free contacts for six functions ,
•
RF Fault. This provides indication of low Forward power.
•
VSWR Fault. This provides indication of High reflected power.
•
TEMP Fault. This provides indication of High temperature at RF PA.
•
PSU Fault. This provides indication of internal PSU fault.
•
STEREO Indication. This provides indication of Stereo Pilot (19kHz)
•
PLL Lock. This provides indication of Synthesizer in Lock.
The
Pilot detection is routed from the Display module via PL6 pin 6 and TR5/RL4/c .
The PLL Lock detection is derived from the Synthesizer module via PL5 pin 1 and
TR6/RL5/c .
The Enable input, on PL7 pin 13 requires a ground connection to disable the RF PA. This is
done via D29, D23, and TR4 to PL2 pin2 .
The Mono/Stereo input, on PL7 pin 14 requires a ground connection for Mono. This is only
used when the Stereo coder option is installed.
The +12VS voltage output at PL7 pin 15, is a 12V/20mA current source used for test
purposes and external control use.
3.
DISPLAY MODULE (980509)
a) Psu and Input requirements
The power supply input is connected at PL1 pin 24 and 25 . This dc input is nominally +21.5V
with the 0V connection at PL1 pin 1 and 2 . The -12V dc input is connected to PL1 pin 21 .
IC3 provides the internal +12V supply and IC12 provides the +5V .
PL1 FUNCTION TABLE
PL1 Function Comment
PL1 pin 1 0V Ground connection
PL1 pin 2 0V Ground connection
PL1 pin 3 MPX Input MPX metering input
PL1 pin 4 Lock (indication) Provides data for Led D8
PL1 pin 5 Enable (indication) Provides data for Led D7
PL1 pin 6 Pilot (Decoder output) +9V nom. for detection
PL1 pin 7 Pre emphasis (indication) Provides data for Led D1
PL1 pin 8 RF Fault (indication) Provides data for Led D2