Comdel CX600 Series, Руководство пользователя

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The high current required by the RF power amplifier (PA) is monitored by the HALL EFFECT CURRENT
MONITOR PCB (Figure FA0502RX) mounted on the 40V DC filter capacitor. This PCB uses a Hall effect
device to monitor the DC current feeding the PA600 RF power amplifier.
C. Oscillator Control Board (OCB)
The oscillator control board (Figure FA0403RX) has six parts, oscillator clock, three stages of gain, circuitry
for output power control and monitoring circuitry. The oscillator clock is a TTL compatible output device that
determines the frequency of operation. This square signal is amplified by three tuned stages of gain,
producing a relatively clean sinusoidal 1 watt output. The DC voltage that powers the last gain stage is
adjustable through control transistor Q5 to control the RF output level of the OCB.
The gain control circuitry smoothes output control and stabilizes output power against line and load
variations and limits output power during high VSWR conditions. Control is achieved through the LM 356
operational amplifier, IC1. This op-amp compares the forward power signal (from the power monitor board) to
that of the DC reference level applied to the non-inverting input. The reference level is set either from the
front panel potentiometer or from Pin 5 of the J1 connector.
The LM 356 drives the gain control transistor, Q5, until enough signal from the forward power detector in the
directional coupler is applied to the inverting input to the op-amp. When the inverting signal equals the
reference voltage on the non-inverting input the drive level holds constant.
The non-inverting input is also the point to which some of the protection circuits connect. The CX controller
pulls this point down when load conditions bring the amplifiers near their over-voltage, or over-current limits.
This limits the drive to the amplifiers until the match between the generator and the load is corrected.
The reflected power limiter performs in the same way when the signal from the reflected power detector in the
directional coupler reaches a pre-set limit. The Q6 transistor does the pull-down function until SWR
conditions are within safe limits. The OCB also includes linearizing circuitry allowing both forward and
reflected analog power level signals to appear at connector J1 as linear presentations of the incident and
reflected RF output power. Two squaring ICs U2 and U4 are used to condition the square law signals from the
directional couplers.
Typical Specifications
(OCB)
Output load impedance 50 ohms
Output RF power level 1 watt (max)
Input power Pin 10 +15 VDC at 170 mA max
Pin 8 -5 VDC at 24 mA max
Remote power control input impedance
Pin 2 on J1 2 K ohm
Reflected power limit Internally set to 100W
D. Driver
The CX600 driver (Figure FA0002RX) is a two-stage Class "C" amplifier with feedback. The first transistor
amplifies a 1 watt (typical) input from the OCB to about 5 watts. The circuitry between the two stages include
two wideband impedance matching transformers and a loss section. The loss sectio n provides added stability
to the system and isolation between stages. The second stage of the driver sends 20 watts (max) to the driver
output connector. There are no adjustments or tuning required for this module.