Please be aware that the distance/range stated in the quick start guide is for use in the optimum conditions (No interference from other wireless devices, not blocking of the signal etc).
If the optimum conditions are not met then you can expect a reduced range/distance during use. 

Please refer to the following from the Quick Start Guide on using your ULM302MIC. 

1. For best performance, avoid placing the receiver close to radio frequency generating equipment such as computers, wireless access points,
cell phones or microwave ovens.

2. It is recommended to use only one set of ULM302MIC at the same time / location (2 microphones with 1 receiver).

3. The wireless operation might cause trouble when two or more sets of ULM300 series models are used simultaneously. In this case you should
keep a minimum distance of 1-2 meters between each microphone, between the mics and receiver, and 10-15 meters between all used ULM300
series sets.