Modulation Manual
Different modes of communication in amateur radio—AM, FM, SSB, digital modes like FT8, PSK31, RTTY, DMR, and more—are suited to specific situations. Your choice depends on distance, noise conditions, equipment, purpose, and legal constraints.
When and Why to Choose Different Modes
|
Scenario |
Best Mode(s) |
Why It Works Well |
|---|---|---|
| Local Chat via Repeater | FM (VHF/UHF) | Clear voice, easy to set up, supported by repeaters |
| Long-Distance Voice (dx0 | SSB (HF) | Narrow bandwidth, efficient over hundreds/thousands of miles |
| Low-Power (QRP) Operation | CW, FT8, PSK31 | Extremely efficient at weak signal communication |
| Contesting / Quick QSO's | SSB, CW, FT8 | Short, fast, bandwidth-efficient exchanges |
| Emergency Communications (EMCOMM) | FM, SSB, Winlink (email) | Dependable, compatible with public service agencies |
| Digital Text Chatting | PSK31, Olivia, RTTY | Narrow bandwidth, good for low-power, low-noise |
| Digital Voice | DMR, Fusion, D-STAR | Internet-linked talk groups, clean audio |
| Satellite Communication | SSB, FM | Narrower modes fit satellite constraints better |
| Experimentation / Development | All Modes + SSTV, APRS | Test and explore technologies (slow-scan TV, GPS beacons) |
Legal & Practical Considerations
Band Plans
Band plans are non-enforceable guidelines created by the amateur radio community to reduce interference.
For example, digital modes have “gentleman’s agreements” about which parts of a band they use. If you transmit SSB where FT8 is common, you'll cause disruption.
Licensing Privileges
Each license class (Technician, General, Extra in the U.S.) has access to different parts of the HF/VHF/UHF spectrum:
FM Voice (2m, 70cm) - Technician +
SSB Voice (20m, 40m) - General or Extra
FT8, PSK31 (HF Bands) - General or Extra
DMR/Fusion (UHF/VHF) - Technician +
CW [Morse] (Many HF Bands) - Technician has limited access, General+ more
Technician licensees can use digital modes, but only on a limited set of HF frequencies.
Mode Bandwidth and Interference
Modes like AM and wide FM take up significantly more space than SSB or FT8.
If you're in a crowded band (like 20m on a weekend), it's courteous and efficient to use narrow-bandwidth modes like SSB or digital.
FT8, for instance, fits dozens of simultaneous QSOs in the space of one SSB voice transmission.
Equipment Capability
Some radios only support analog modes (like FM, SSB).
Others (e.g., SDRs or digital transceivers) support digital audio, digital data, and PC integration.
Use what your rig allows—but be mindful of what’s legal for your license and appropriate for your band.
Summary
Choosing the right mode isn't just about preference—it's about respecting the band, operating efficiently, staying legal, and using the best tool for the job. As you advance, you'll get a feel for the right mode for any given situation:
Use FM for local voice, SSB for long-distance, and FT8/PSK31 when conditions are poor.
Match your mode to the spectrum, goal, and legal privileges.