The HR70 is a digital display analog FM transmitter. Apply a signal to the XLR or RCA inputs of the HR70. Select what frequency you would like to broadcast those signals on –87.5 to 108 MHz– and you are now sending signals via FM radio, assuming the antenna is connected properly. The HR70 also has a talk over circuit built in. Even though the HR70 is a micro power RF transmitter and requires no FCC licence, for it to function properly good RF practices still apply.
The wire antenna that is provided is set up for the middle of the band or about 92MHz. For any transmitter to operate at its′s best, it must be earth grounded. You can think if it sort of “pushing” the signal against the earth. Range can vary widely, depending on grounding, antenna placement, obstructing building/walls, etc.. We have had people report ranges of 150′ or more down to 30′ or so. Some experimenting may be required at your venue to find the optimum installation for your situation.
What is the maximum distance an FM transmitter can broadcast without a license? The quick answer is approximately 200 feet for an FM Transmitter covered under Part 15 (Read FCC Public Notice dated July 24, 1991). The full answer is much more complicated than that: 250 µV/meter @ 3 meters (also measured as 48 dBuV/m).