TR-50 Theory of Operation
Theory of Operation
I. Power Control
The control board draws a general 13.8V dc power supply, which is converted through U1,
a 3-terminal regulator, to 8.0V dc for the receiver and transmitter.
Fig. 1 Power Supply Block Diagram
II. Relay Control
When a valid signal is detected, the COR goes low and trigger PTT of the transmitter. At
the same time, the audio output from discriminator is routed to MIC input of the transmitter.
The potentiometer VR3 is used to adjust the receive audio output to the proper level for
transmit audio deviation.
III. Float Charging Function
The TR-50 provides selectable AC (100-240V ac) power supply. Normally users can equip
battery back-up system connected to the external DC jack with floating charge function in
the mean time. This provides auto-revert to DC battery once the AC mains fails.
IV. Fan Control
This repeater provides three options of cooling fan control: PTT controlled, temperature
controlled and continuous operation. The power supply of the fan is controlled through a
5V voltage detector, HT7050A. When the input is above 5V, the output is high-Z; when
lower than 5V, the output goes low.
