RFL 9780 RFL Electronics Inc.
April 8, 2003 2-14 (973) 334-3100
2.8.4 POWER AMPLIFIER MODULE
The RFL 9780 Power Amplifier is driven by the transmitter module, and raises the power of the
transmitter to the level chosen for the application. It also includes a level monitoring circuit that will
send a TX FAIL alarm to the logic module if the transmitter fails. The amplifier has a transformer-
isolated output, and a 50Ω output impedance. Section 9 of this manual contains additional information
on the RFL 9780 Power Amplifier.
2.8.5 OUTPUT FILTER MODULES
RFL 9780 Output Filter modules are used to reduce the harmonic content of the RFL 9780 Power
Amplifier’s output signal to a level that is at least 55 dB below the carrier level. In order to cover the
RFL 9780's entire operating range (30 kHz to 537.5 kHz), there are four different RFL 9780 Output
Filters. A fifth Output Filter module is available which covers a wider frequency range. Refer to Table
2-2 for approximate filter ranges. Four out of the five filters listed are equipped with jumpers for
selecting the desired passband frequency range and the fifth has a fixed range, which covers the top of
the RFL 9780's frequency band. All five filters are entirely passive, and require no input power for
proper operation. Some of the Filter modules have additional circuitry to sense impedance mismatch to
the load (reflected power). For additional information on the RFL 9780 Output Filter modules, refer to
Section 10 of this manual.
2.8.6 RECEIVING SECTION
The RFL 9780 Receiving section consists of the following 4 modules: RF Interface, IF/BF, Carrier
Level Indicator and Limiter/Slicer. Each of these modules is described briefly in paragraphs 2.8.6.1
through 2.8.6.4. Additional information on these modules can be found in Sections 11 through 14 of
this manual.
2.8.6.1 RF Interface Module
The RFL 9780 RF Interface Module provides an interface between the Input I/O module and the IF/BF
module. It consists of an attenuator, an amplifier, and a programmable filter, which is used to attenuate
excess rf energy from the receiver input. The filter is programmable from 30Khz to 535Khz using a
bank of DIP switches, SW1 through SW4.
2.8.6.2 IF/BF Programmable Demodulator Module
The RFL 9780 IF/BF Programmable Demodulator Module demodulates the received input signal and
brings it down to the 9780’s baseband frequency of 4 kHz.
2.8.6.3 Carrier Level Indicator Module
The input stage of the Carrier Level Indicator Module is a narrow band filter, which sets the basic
bandwidth for the receiver section. 200, 500 and 1000 Hz filters are available.
The module also contains circuitry to monitor and display the received signal level. The display is a
digital panel meter which reads directly in dB and is visible with the front panel of the unit closed. The
module also monitors the signal and sets an alarm bit in the logic module if the level falls below a user
settable limit.
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