Radio Frequency (RF)

The wireless transmitters used for Project H2O use radio frequencies (RF) to transmit data to Madison Water Utility. The exposures to RF from a wireless meter are much lower than many common household devices, including cell phones, laptop computers, and microwave ovens. The meters use about 1/4 the power of a cell phone, and total daily transmission time is less than 15 seconds per day*.

Comparison of Typical Radio Frequency (RF) Exposures

Relative Power Density in microwatts per square centimeter (µW/cm2)

FM radio or TV broadcast station signal 0.005
SmartMeter device at 10 feet 0.1
Cyber cafe (Wi-Fi) 10 - 20
Laptop computer 10 - 20
Cell phone held up to head 30 - 10,000
Walkie-Talkie at head 500 - 42,000

Source: Richard Tell Associates, Inc.


In addition to wireless transmitters at the meters, there are 11 collectors and 141 repeaters across the city to relay information back to Madison Water Utility.

Collector/Repeater Power Operating Range:

Average Power – 10 Watts (battery trickle charge)

Peak Power - 50 Watts

Frequently Asked Questions

Is it safe? Are there any health hazards associated with these devices?

Wireless meters use very low power radio frequencies (RF) that result in much smaller levels of exposure than many existing common household electronic devices. Public Health Madison and Dane County has completed a report on this type of system which comes to the following conclusion:

"A thorough review of the relevant literature suggests that there is little evidence to support an association with any potential health effects that may result from the installation and/or normal operation of the smart meter. This conclusion was based upon the reported infrequent and low level of RF emissions from the device and the lack of data supporting an association between RF exposures at this level to the development of non-thermal effects in exposed individuals. Therefore, PHMDC supports the deployment of AMI network technology proposed by the City of Madison Water Utility and do not foresee any potential individual and/or community health danger due to the installation and operation of this technology."

Additional resources are linked at the bottom of this page.

Will the radio transmitters interfere with WiFi, a security system, cell phone or other RF devices?

The radio transmitters operate in compliance with FCC regulations that require coexistence with other RF devices operating in the 902-928 MHz band. The low-power design, short transmission time, and frequency hopping techniques of the units help reduce the probability of interference with other wireless devices. The likelihood of interference between the radio transmitters and other RF devices is extremely low.

Radiofrequency Output Information for the Water Meter Communication Module

  • Operating frequency of the meter communication module is in the Industrial, Scientific, and Medical (ISM) band at frequencies from 902 to 928 MHz
  • The transmission time is extremely short, less than 10 milliseconds.
  • The module transmits a message every minute. Total transmission time is less than 15 seconds per day.
  • When not transmitting data, the module radio remains off.
  • The module's power output is 0.516W (the average light bulb is 60W).
  • The water module power density is 0.215mW/cm2 at 20 cm. The FCC guideline for Maximum Permissible Exposure (MPE) is 0.610 mW/cm2 at 20 cm.
  • FCC ID: EWQ100WC.
  • IC: 864D-100WC

RF Output Information for the Data Collectors and Repeaters

The current configuration of the fixed network system includes 91 repeaters located throughout the city on street light poles, and 10 data collectors on existing MWU facilities or other governmental buildings.

  • The data collector ccu power density is .0014 mW/cm2 at 20 feet.
  • The repeater ccu power density is .0013 mW/cm2 at 20 feet.


* Transmission time is less than 10 milliseconds and the module transmits a message every minute. Therefore, 10 milliseconds times 60 minutes in an hour times 24 hours in a day equals 14,400 milliseconds or 14.4 seconds per day.

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