The term frequency used in wireless applications describes the primary radio carrier where the data is modulated.  In trying to identify the best frequency for your application, there’s no such thing as a good frequency or a bad frequency. Each frequency simply has advantages and disadvantages. It’s the balancing of those characteristics that allows us to identify the most appropriate frequency for your specific application.

The frequencies used by industrial Ethernet and serial radios can be broken into two main groups – those that are individually authorized from the Federal Communications Commission (FCC) known as licensed frequencies and another that group that operate in specific frequency bands and power levels known as unlicensed frequencies. There’s also an industry-specific set of frequencies that we’ll touch on later.

FCC-Licensed Frequencies

The FCC-licensed frequencies most commonly used in industrial wireless networks are:

  • 150-174MHz
  • 217-220MHz
  • 450-470MHz

An inherent advantage to this group is the network owner’s exclusive use of the licensed frequency, reducing the likelihood of interference from other sources. Additional advantages include:

  • Greater range (15-30 miles)
  • Less terrain/vegetation signal loss
  • Line of sight flexibility
  • Lower signal loss through the cable and connectors

But the use of FCC-licensed frequencies also creates certain boundaries that wireless network owners need to consider. These include:

  • Limited bandwidths creating data rates from 9,600 – 64Kbps
  • A higher noise floor, requiring more receive signal
  • Larger antennas, with the size based on the wavelength in use

License-Free Frequencies

Common license-free frequencies for industrial applications are:

  • 900MHz
  • 2.4GHz
  • 5.8GHz

Using a license-free frequency automatically saves you the time and expense of securing an FCC license, which can require lead times of up to six months. License-free options also offer certain advantages such as:

  • Larger bandwidths allowing higher data rates (up to 300Mbps)
  • Simple Ethernet bridging/networks
  • Self-healing MESH networking for redundancy and reliability
  • Wi-Fi access for third-party devices (2.4GHz and 5.8GHz)

The inherent nature of license-free frequencies also presents their most basic disadvantage: Since the frequencies are unlicensed, anyone can use them, and the shared use of these resources continues to evolve. Other boundaries involved in the use of license-free frequencies include:

  • Lower tolerance of line-of-site obstructions
  • Reduced range, with the frequency and power limited by the FCC

The reduced range frequently entails additional system costs to cover the necessary repeaters.

Exclusive-Use Frequencies

Municipal water/wastewater treatment applications also have exclusive access to 4.9GHz, a high-speed frequency licensed specifically by the FCC for public safety concerns. This exclusive use offers advantages like:

  • Virtually no user interference
  • Greater security
  • High data rates (up to 72Mbps)
  • Simple Ethernet bridging/networks
  • Self-healing MESH networking for redundancy and reliability

The exclusivity also represents this frequency’s most basic limitation: it can only be used for municipal applications. Other boundaries to consider include:

  • The use of proprietary technology, precluding Wi-Fi access
  • The requirement for absolute line of sight, necessitating the use of repeaters and increasing the system’s overall cost

Designing the right wireless network for your industrial application requires a significant level of expertise and a clear understanding of the advantages and boundaries presented by each frequency. Contact ESTeem to learn how we can help you achieve your most critical communication goals.

Learn more:
Which Unlicensed Frequency is Best for Your Application?
Industrial Wireless Network Antennas Simplified