Another problem with the 70’s wireless microphone gear was interference. FCC regulations were not enforced very strictly and consequently many commercial transmitters used by cabs, businesses, radiated on frequencies shared by the wireless microphones. Or, more often, the wireless microphones were manufactured to operate on frequencies allocated for use by much larger and more powerful commercial transmitters in use throughout many cities. This created the problem that when a powerful transmitter, say for a taxi company, made a broadcast, the broadcast could interfere with or actually be heard through the wireless microphone receiver and amplified so that the audience could hear it. To compound matters, the person making the broadcast sometimes used harsh language not suitable for minors or acceptable to church-goers and would sometimes be heard through the church audio system, clear as a bell. These occurrences produced no small frustration for the audio engineers and embarrassment for the event organizers and pastors.
Additionally, even in locations where the larger more powerful radio transmitters operated on legally defined frequencies, and the manufactures of the wireless microphone/receiver equipment also operated in legal frequencies, there arose the problem of ‘beat frequencies’. Beat frequencies are radio signals which are created by two or more transmitters interacting with one another to generate an entirely new and unintentional signal or set of signals. For example, two taxi cab drivers parked close to one another decide to make a call to headquarters at the same time, both transmitting on slightly different radio frequencies. Taxi cab radio A interacts with taxi cab radio B, creating an entirely new radio signal, usually between both frequencies, often referred to as a ‘beat frequency’. Worse yet, more than one beat frequency can be created, resulting in many new radio signals entering the RF spectrum. If a wireless receiver happens to operating on a frequency near the newly created beat frequency, then interference could occur.