Looks to be a very crude setup when it comes to TX/RX switching.
The way this circuit diagram is drawn, top half is a transmitter train, and bottom half is a receiver train. Now, find a line that connects to a pair of diodes D21 1 and 2. It is located on lower right corner and a line goes from TX section to RX section.
Transmitter is always connected to the antenna. Receiver has a pair of diodes to prevent more than 0.7V of RF going into the section. Also, Q47 acts as a shunt to short out the receiver input when transmitter is active.
I guess for a 4W RF output, this must work well enough. On larger radio, I've seen using PIN diode as switch on receiver front end. On even larger, I've seen vacuum relay.