I would not use a radio from the 1980's. Many problems:

1. This would not be a narrow band radio and would be therefore, illegal to operate.
2. This would not likely be an FM radio. AM is more prone to interference.
3. The receiver would not likely be double conversion. Much more prone to interference.
4. The original NiCD batteries would be long gone. Replacement batteries alone could run $50 for TX and RX.
5. A new 6ch narrow band FM radio with double conversion receiver and NEW batteries can be had for perhaps $150.
6. Why risk your model and endanger the models of others?

Get a new (or used late model) radio.