LTE Band 20 and Band 71: Frequencies and mW-to-dBm Conversion

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LTE Band 20 and LTE Band 71 are paired low-band frequency allocations used for wide-area cellular coverage. Band 20 occupies the 800 MHz range and is strongly associated with Europe, while Band 71 occupies the 600 MHz range and is primarily used in North America. Both use frequency-division duplexing (FDD), with separate uplink and downlink ranges.

The frequency band explains part of a network’s propagation behavior, but it does not guarantee coverage by itself. Antenna height, transmit power, bandwidth, terrain, building materials, network design, and device support also determine usable service. Radio specifications commonly express power in milliwatts (mW) or watts, while RF engineering often uses decibel-milliwatts (dBm).

LTE Band 20: European 800 MHz FDD spectrum

LTE Band 20, also called the European 800 MHz band, uses the following paired ranges:

  • Downlink: 791–821 MHz
  • Uplink: 832–862 MHz
  • Duplexing: FDD
  • Duplex spacing: 41 MHz between corresponding uplink and downlink frequencies

In an FDD system, the base station transmits to the device on the downlink range while the device transmits back on the uplink range. The two directions operate at the same time on separate frequencies. The 11 MHz separation between the upper downlink edge and lower uplink edge provides a duplex gap, while practical deployments also account for guard bands and channel bandwidth limits.

Band 20 was created in the European 800 MHz digital-dividend spectrum and has been deployed widely across Europe. It is also used in other regions that adopted compatible 800 MHz arrangements. National licensing, refarming decisions, and operator channel assignments determine whether a particular network actually provides Band 20 service.

The band is valuable for broad rural coverage and improved indoor reach compared with higher-frequency LTE allocations. Typical LTE channel bandwidths can include 5, 10, or 20 MHz, subject to the operator’s license and network configuration. A Band 20-capable handset may therefore connect over a wide area, but the available bandwidth and performance depend on the specific cell.

Device support is common in international and European phone models, routers, mobile hotspots, and industrial modems. Compatibility still requires more than a frequency-band listing. The modem must support the required LTE category, carrier aggregation combinations, regional firmware, and the operator’s authentication and network features. A device that supports Band 20 but lacks the operator’s other required bands may have limited capacity or may fall back to another radio technology.

LTE Band 71: North American 600 MHz FDD spectrum

LTE Band 71 uses lower-frequency 600 MHz spectrum and has this paired structure:

  • Downlink: 617–652 MHz
  • Uplink: 663–698 MHz
  • Duplexing: FDD
  • Duplex spacing: 46 MHz between corresponding uplink and downlink frequencies

Band 71 was developed from the North American 600 MHz broadcast-spectrum repurposing process and is especially associated with United States deployments. The allocation is divided into blocks that operators may hold in different combinations, so a network may use only part of the full 617–698 MHz range. Canada and other markets may use related 600 MHz arrangements, but national band plans and device certifications must be checked separately.

Compared with Band 20, Band 71 operates at lower frequencies. That generally supports longer propagation distances and better penetration through some building materials, allowing operators to cover large rural areas or improve the reach of a low-band layer. The lower frequency also requires antennas and RF front ends designed for the 600 MHz range.

Band 71 support is concentrated in North American versions of phones, fixed-wireless terminals, cellular routers, and IoT equipment. Many international models omit it even when they support Band 20 and other LTE bands. Conversely, a device designed for the United States may support Band 71 but omit European bands or lack the frequency combinations needed on another operator’s network.

As with Band 20, the downlink and uplink ranges do not describe a guaranteed user experience. Network loading, the assigned channel block, uplink limitations, antenna placement, and the device’s supported LTE category affect throughput. Band 71 can provide a strong coverage layer while higher bands supply additional capacity in dense locations.

Low-band propagation, compatibility, and deployment choices

Both bands are considered low-band LTE, but their propagation characteristics are not identical. Lower frequencies generally experience less free-space path loss over the same distance than higher frequencies. They can also diffract more effectively around some obstacles and often provide better building penetration. These are useful tendencies, not standalone coverage guarantees.

  • Band 20 at about 800 MHz: A mature European coverage layer with broad handset and infrastructure support. It is often used to extend service across rural areas and inside buildings.
  • Band 71 at about 600 MHz: A lower-frequency North American coverage layer suited to wide geographic cells, rural deployment, and improved reach from existing sites.

For a network operator, the choice is usually determined by licensed spectrum rather than by a simple preference between the two bands. Band 20 cannot substitute for Band 71 on a device or network that lacks compatible RF hardware, and Band 71 cannot substitute for Band 20 in a European deployment unless the local operator has a compatible 600 MHz allocation.

Device compatibility should be evaluated at several levels:

  • Band support: The modem and RF front end must explicitly support Band 20 or Band 71.
  • Regional variant: The same phone model name may have different frequency support in European, North American, and Asian versions.
  • Carrier aggregation: The device must support the band combinations used by the network to combine low-band coverage with mid-band capacity.
  • Uplink capability: A device may receive a strong downlink while its lower-power uplink remains the limiting direction.
  • Certification and provisioning: Operator approval, firmware configuration, SIM provisioning, and regulatory certification can affect actual access.

Coverage planning also distinguishes conducted power, measured at a radio connector, from radiated power, which accounts for antenna gain and losses. A larger transmit-power figure does not automatically create a larger service area. Noise, interference, receiver sensitivity, antenna pattern, terrain, and the required data rate all influence the cell edge.

Convert milliwatts to dBm with practical examples

dBm is a logarithmic power unit referenced to 1 milliwatt. The conversion from milliwatts to dBm is:

Power in dBm = 10 × log10(power in mW)

The inverse conversion is:

Power in mW = 10(power in dBm ÷ 10)

Only positive power values can be converted with the logarithm. A value below 1 mW produces a negative dBm result, 1 mW equals 0 dBm, and values above 1 mW produce positive dBm values.

Worked milliwatt-to-dBm conversions

  • 0.1 mW: 10 × log10(0.1) = −10 dBm
  • 0.5 mW: 10 × log10(0.5) = −3.01 dBm
  • 1 mW: 10 × log10(1) = 0 dBm
  • 2 mW: 10 × log10(2) = 3.01 dBm
  • 10 mW: 10 × log10(10) = 10 dBm
  • 100 mW: 10 × log10(100) = 20 dBm
  • 1,000 mW: 10 × log10(1,000) = 30 dBm

Watts must first be converted to milliwatts: 1 W = 1,000 mW. Therefore, 0.1 W equals 100 mW and converts to 20 dBm; 1 W equals 1,000 mW and converts to 30 dBm; and 5 W equals 5,000 mW and converts to approximately 36.99 dBm.

Useful reference points follow a tenfold pattern: 1 mW is 0 dBm, 10 mW is 10 dBm, 100 mW is 20 dBm, and 1,000 mW is 30 dBm. Doubling power adds about 3.01 dB, while halving power subtracts about 3.01 dB. When reading an LTE specification, the result should also be labeled as conducted power, EIRP, or another defined measurement, because those measurements are not interchangeable.