Bandwidth: Wide vs Narrow

Bandwidth refers to how much radio spectrum a channel occupies. On GMRS, channels use either 25 kHz wideband or 12.5 kHz narrowband, and which one applies depends on the channel number. Getting this wrong can cause poor audio quality or interference with adjacent channels.

Which channels use which bandwidth

• Channels 1–7 (462.5625–462.7125 MHz): 25 kHz wideband. These are the main simplex/repeater output channels
• Channels 8–14 (467.5625–467.7125 MHz): 12.5 kHz narrowband. These are the repeater input channels, also usable for low-power simplex
• Channels 15–22 (462.550–462.725 MHz): 25 kHz wideband. These are the shared GMRS/FRS interstitial channels

Why it matters

Wideband transmissions carry more audio information, resulting in louder, fuller sound. Narrowband uses less spectrum but the audio is quieter and slightly more compressed. The key issue is mismatch:

• Wideband radio on a narrowband channel: your signal bleeds into adjacent channels, causing interference to other users. Your transmitted audio is also wider than the receiver expects, which can sound distorted
• Narrowband radio on a wideband channel: your audio will sound quiet and thin to other stations. You're not causing interference, but you're not using the full channel capacity either

Most radios handle this automatically

If your radio is programmed with the standard GMRS channel plan (and most factory-programmed radios are), it already uses the correct bandwidth for each channel. The only time you need to worry about this is when programming with CHIRP or manually entering frequencies:

1. Set channels 1–7 and 15–22 to Wide (25 kHz)
2. Set channels 8–14 to Narrow (12.5 kHz)

Interoperability

When communicating with FRS radios on the shared channels (15–22), both sides use 25 kHz wideband, so there's no mismatch. FRS radios on channels 8–14 also use narrowband. The bandwidth settings are defined by the FCC in Part 95, so any properly type-accepted radio should already be configured correctly out of the box.

If you're hearing distorted or unusually quiet audio from another station, a bandwidth mismatch is one of the first things to check — especially if they're using a radio programmed manually or through software. See also: Channels and Frequencies for the full GMRS channel plan.