Emissions Designator 4M21F9W

4M21F9W is an FCC emission designator. It describes an emission with an indicated necessary bandwidth of 4.21 MHz, angle modulation, frequency modulation, composite digital and analog channels, carrying combination of information types listed above.

Emission designators are used on FCC grants and equipment authorization records to summarize the radio emission being authorized. They help identify how wide the emission is, how the carrier is modulated, whether the signal is analog or digital, and what kind of information is being transmitted.

They are useful for comparing radios, matching a grant to a modulation type, and understanding whether an authorization covers voice, data, telemetry, video, or mixed services.

An emission designator is not the whole authorization. It does not by itself prove the exact channel plan, antenna limits, output power, or every condition on the grant. For those details, read the FCC grant and the related test reports.

The bandwidth prefix uses a letter as both the decimal point and the unit. For example, 20K0 means 20.0 kHz, 8M91 means 8.91 MHz, and 345K means 345 kHz.

For 4M21F9W, the first four characters decode to 4.21 MHz. The remaining symbols describe modulation, signal nature, and information type.

The FCC classification system for emission, modulation, and transmission characteristics is defined in 47 CFR 2.201. The FCC also indicates that the full emission designation is preceded by the necessary bandwidth when the full designation is required.

• FCC emission designators combine emission classification with the necessary bandwidth of the emission.
• The three required symbols identify carrier modulation, nature of the modulating signal, and type of information transmitted.
• Fourth and fifth symbols may be added for a more complete description, but the Commission does not require them.
• When frequency modulation F is indicated, phase modulation G is also acceptable under the FCC note in this section.
• Pulse-code or other quantized direct modulation should be classified under the amplitude or angle modulation groups, not merely as pulse emission.
• The information symbol does not include constant, unvarying information such as standard frequency emissions, continuous wave emissions, or pulse radars.
• Type B damped-wave emission is an FCC exception and is forbidden.
• When the full designation is needed, the emission symbol is preceded by the necessary bandwidth as indicated in 47 CFR 2.202(b)(1).