User's Manual

The outer power control can be performed by connecting filters “CTRL” or “Sh/D” to the ground, or by

connecting a resistor between one of mentioned filters and the ground. Usage of the filter “CTRL” allows to

reduce the output power down to – 1 dB relatively to the set up level. Connecting of the filter “Sh/D” to the

ground gives a power decrease down to -6.5 dB.

The current limiters in the Final Stage Board do not allow for DC current of the module U31 or U51 to rise

above 11A. The voltage drops on the current shunts R49 and R69 are monitored by the microcircuits U33 and

U53. The voltages at the outputs of U33 and U53 come to comparators U32, U52. If one of mentioned voltages

exceeds 2.5 V, the voltage at the output of U32 or U52 decreases, and the voltage at the emitter of Q32 or Q52

(the bias voltage of U31 or U51) goes down, reducing the gain of U31 or U51. At the same moment, Q31 or

Q51 opens and LED D31 or D51 start shining, indicating the current limiter activation.

Monitoring Circuitry Description.

There is the LED Board for the status indication of unit. Green LED “DC ON” goes on, when DC power supply

voltage is applied. Any red LED is on in the case of alarm. Also, with the aid of Q17 in the Control Board, the

circuitry produces the common alarm signal: low voltage at the filter “ALARM” of the unit.

“LOW OUTPUT” LED turns on, when the output power fails below -1 dB down from the set up level. The

activating signal is produced by the OA U3-B in the Control Board, which opens the key Q14, sending the

voltage to LED. This signal may be blocked by the open Q13 in the case of high load VSWR that can be the

primary cause of the power decrease. Q13 is connected to the output of OA U2-C, which compares voltages,

coming from forwarded and reversed power detectors.

“HIGH VSWR” LED turns on, when the voltage of reversed power detector is greater than ~117% of the

levered voltage of forwarded power detector. Both levels are compared by OA U2-D. In the case of alarm, the

key Q12 opens, sending the voltage to LED.

“HIGH TEMP” LED turns on, when the temperature of heatsink reaches +85˚C; the thermal switch contacts are

Closed, and the key Q8 is open.

3. Construction.

Unit dimensions are 19” W x 6-3/4” H x 5” D. It is intended for the rack mounting in the 19’ cabinet.

Four indicating LED are visible through holes in the front panel. All connectors are accessible from the back

side of unit. The cooling fan is also placed on the back of chassis.

4. Installation Guide.

Unit is intended for a rack installation in a standard 19” cabinet, where it requires 4U high slot. The installation

shall provide a proper air access to the unit; no obstacle for air is allowed closer than 3” from fan and air exits.

Copper wires # 10 AWG shall be use in DC power line. Wires shall be crimped to ring terminals.

5. Operation Guide

- The power supply voltage should be in the limits 12.8 V…14.8 V;

- Do not apply RF signal out of rated 136…174 MHz frequency range;

- The input RF power should be in the rated range - see Table 1 in Block-Diagram;

- Do not destroy the sealing and other labels.