Technical Manual
GUARDIAN VHF 110W MOBILE 2-9
2.4.14 Test Interface
The test interface provides the following functions:
Joint test action group (JTAG) connector access for board test and Flash boot sector programming
Board reset and control access
Board power supply and on-off switching access
H8 serial debug port access
2.4.15 LED
The control logic incorporates a 3-color LED used for status information. It is controlled by the FPGA to show red,
green, or off. It is optically coupled to the top face of the radio by a light pipe. The hardware is configured so
during hardware reset, before the keypad MPU software is running, the LEDs are off.
2.4.16 RECM Power Consumption
The control logic operates at input voltage 7.7V. The average current consumption of the control logic is:
Standby mode: 60 mA
Receive mode @ 500 mW: 330 mA
Transmit mode @ 2W: 1,000 mA
Transmit mode @ 5W: 1,500 mA
2.5 RECM Transceiver
RF shields covers the board.
2.5.1 Interface
J2 is the transceiver antenna connector. RF signals are transmitted and received through this surface mount RF
connector. Transmitted and received RF signals are routed from this connector through a short RF cable to the
RX/TX relay on the Motherboard.
2.5.1.1 Transmit Chain
The pre-driver amplifier (Q7, etc.) amplifies the TXLO signal from the synthesizer section. The Q7 output power is
typically 13 dBm measured at C77/R44/R49 node.
R44, R49, and R52 are part of a 3 dB pie attenuator network. The gain control is made up of CR5, CR6, and
associated components. This circuit yields more than 50 dB of useful attenuation range. The circuit is part of a
DAC controlled closed loop system, in conjunction with the detector/power control circuit (U12, U13, and
associated components), which controls the transmitter output power level. The power amplifier (PA) is a
Mitsubishi M68776, 7.2V, 6W gained controlled power amplifier.
The harmonic filter (C209, L30, C81, C82, L31, C83, and C84) attenuates harmonics created by the power
amplifier. The harmonic filter insertion loss is 0.4 dB typically at 174 MHz. The output of the harmonic filter
connects to the 20 dB coupler (U12). This coupler is part of a DAC-controlled closed loop system designed to set
the transmitter output power level. The insertion loss through the coupler (U12-1 to U12-3) is 0.2 dB typically.
2.5.1.2 Power Amplifier Control
Transmit output power level is controlled by the detector/power control circuit and the gain control amplifier input
via VCONTROL. This closed loop system is designed to keep the transmitter output power constant over variations
in temperature, transmitter supply voltage (7.5VT), and RF power levels into the transmit chain. The detector/power
control circuit is made up of the 20 dB coupler (U12), an RF rectifier circuit (CR11, CR12, etc.), and an integrator
(U13). The DAC line labeled PWRSET at the non-inverting input of U13 sets the transmitter to the desired power
level. U12-2 samples the transmit signal. The sampled RF signal is rectified by the temperature stable circuitry of
CR11, CR12, etc, and is routed to the inverting input of the integrator at U13-4. The output of the integrator at U13-
1, labeled VCONTROL, controls the gain of the power amplifier. Any change in transmitter output power level is
automatically corrected by the loop.