Use of 4G and 5G technologies for local industrial networks has become feasible in recent years. This paper studies the co-existence of two geographically limited adjacent Time Division Duplex (TDD) local networks through a field measurement campaign. The networks have the same or different TDD frame configurations. The test setup developed to conduct the interference measurement campaign can be used to study both 4G and 5G TDD technologies. Measurement results indicate that non-synchronized networks produce interference and significant decrease in data throughput in neighboring networks. Thus, networks using TDD technology are recommended to use synchronized frame configurations to avoid interference. However, local network applications and their requirements may differ between user organizations, and hence the uplink and downlink data rate requirements are different and may need different TDD frame configurations.