The Yaesu FT-736R CAT interface port uses Transistor-Transistor Logic (TTL) which operates at 0V, 5V levels for "0" (low) and "1" (high) logic
states. Computer RS-232 serial (COM) ports operate at -10V, +10V levels for low and high logic states. You therefore need an RS-232/TTL converter to control this radio.
Yaesu sells a converting interface for about $100 retail. You can build a converter for about $10. You need the following parts:
- (1) DB25 Female 25 pin connector and shell
- (1) 6 Pin DIN plug
- (2) 2N2222A NPN transistors
- (3) 10K resistors
- (1) 11K resistor
- (1) 4.3K resistor
This circuit can be built within the shell of the DB25 connector. Use the schematic diagram below, provided by Eduardo Jacob EA2BAJ, as a
your guide for making the connections.