Free tools Windows power users keep installed
One-click scans. No signup required.
There is no universally best modulation mode. Conventional AM is easiest to receive and remains useful where compatibility and simple tuning matter. SSB normally gives the best combination of narrow bandwidth and transmitter-power efficiency for voice links. DSB-SC removes carrier waste but keeps both sidebands, making it mainly a building block for coherent systems. FM uses more bandwidth in exchange for better amplitude-noise rejection, constant-envelope amplification, and generally cleaner voice or music above its threshold.
In this comparison, AM means conventional double-sideband full-carrier AM (DSB-LC). DSB-SC and SSB are also amplitude-modulation formats in the broad mathematical sense, but they are separated here because their carrier and sideband choices create different engineering trade-offs.
The four modes at a glance
| Mode | Transmitted signal | Typical receiver | Main advantage | Main cost |
|---|---|---|---|---|
| Conventional AM (DSB-LC) | Carrier plus upper and lower sidebands | Envelope detector | Simple, compatible reception | Wastes carrier power and suffers from amplitude noise |
| DSB-SC | Upper and lower sidebands; carrier suppressed | Product detector with coherent carrier | Much better RF power use than full-carrier AM | Still uses two sidebands and needs synchronization |
| SSB, usually SSB-SC | One sideband; carrier normally suppressed | Product detector/BFO with accurate tuning | Minimum bandwidth and excellent information-per-watt potential | More demanding generation, tuning, and carrier reinsertion |
| FM | Carrier frequency varies; amplitude is ideally constant | Discriminator, PLL, or digital FM demodulator | Good amplitude-noise rejection and audio quality | Bandwidth, threshold, and multipath trade-offs |
IEEE describes DSB-SC as carrier-suppressed AM and SSB as AM with one sideband removed: IEEE amplitude-modulation overview. Regulatory emission designators distinguish ordinary AM voice (A3E), SSB voice (J3E), and FM voice (F3E) in FCC technical rules.
How their spectra and bandwidth differ
Let W be the highest baseband frequency. For speech, W is set by the chosen audio filter, not by the modulation label alone.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →#1 Best Overall
- Detachable Display Unit - The display unit and the radio body can be separated. This allows you to place the head remotely. FCC ID: 2BGMW-G90
- Wide Range Auto Antenna Tuner - Unlike other QRP radios, the G90 has a wide-range internal automatic antenna tuner so you can load up your favorite field antenna! The G90 also comes with a built-in mediumwave (AM broadcast) high-pass filter.
- Beautiful Color LCD Screen - All vital operating information is clearly visible in daylight conditions. 48KHZ wide spectrum display with waterfall gives you excellent awareness of the signal conditions around you.
- Easy to Use - You can use the Quick Mode button to turn on or off various functions. Instead of setting up different functions in the menu, you can directly adjust them by pressing corresponding function keys.
- We provide a 18 months warranty on Xiegu G90. As usual, if you modify the radio's hardware, the warranty is void. [Latest Firmware Version] - Firmware V1.81 is available on Radioddity official.
Conventional AM
A full-carrier AM signal has a carrier at fc, an upper sideband above it, and a lower sideband below it. For a baseband extending from DC to W:
BAM ≈ 2W
The sidebands contain the message; the carrier is useful for envelope detection and tuning but carries no new baseband information in the ideal model.
DSB-SC
DSB-SC retains both sidebands and suppresses the carrier:
BDSB-SC ≈ 2W
It therefore occupies approximately the same bandwidth as conventional AM while moving transmitted power into information-bearing components.
SSB
SSB transmits only the upper or lower sideband:
BSSB ≈ W
For a voice signal whose lowest frequency is flow and highest frequency is M, necessary bandwidth is more precisely related to M − flow. USB and LSB are choices of sideband, not different modulation principles. Reduced-carrier SSB transmits a small carrier for tuning assistance; ordinary SSB-SC normally does not.
FM
FM produces a carrier and a series of sidebands. A practical estimate is Carson’s rule:
Rank #2
- Powerful Performance: The QT40 10 meter radio boasts a 40 watts transmission power and 28.000-29.695MHz frequency range that delivers crystal-clear communication over long distances, making it an ideal choice for outdoor enthusiasts, truckers, and emergency responders. FCC ID: T4K-ARESII
- Noise Reduction: With TX and RX digital noise reduction technology, the QT40 ensures that you'll never have to strain to hear or be heard in noisy environments.
- Accurate Signal Meter: The PWR/RX RSSI Signal Meter provides you with a clear picture of your signal strength, helping you to optimize your communication for the best possible results.
- Weather Channel: With its impressive weather band and NOAA alert feature, you can stay ahead of the curve and be prepared for any sudden changes in the weather. Whether you're out camping, hiking, or simply enjoying a day out in the park, this radio has got you covered.
- Customizable Features: The QT40 is equipped with a range of customizable features, including CTCSS/DCS, ASQ, SQ function, RF gain control, TOT, VOX, HI-CUT function, and echo function, giving you complete control over your communication experience.
BFM ≈ 2(Δf + W)
Here Δf is peak deviation. With modulation index β = Δf/W, the estimate becomes 2W(β + 1). Narrowband FM can be relatively compact; wideband FM is much wider. ITU bandwidth guidance gives DSB telephony as approximately 2M, suppressed-carrier SSB telephony as M − flow, and FM as 2M + 2DK: ITU reference material. International necessary-bandwidth definitions are covered by ITU-R SM.1138-3.
Thus, SSB is normally the most bandwidth-efficient of these four for comparable voice audio. AM and DSB-SC are about twice the message bandwidth. FM’s position depends on deviation, audio filtering, and the applicable emission mask; saying simply that “FM always uses more bandwidth” is too broad.
Transmitter power efficiency is not one single metric
Conventional AM
For a single-tone AM signal with modulation index m:
Ptotal = Pc(1 + m²/2)
Sideband power is Pcm²/2, so ideal modulation power efficiency is:
η = m²/(2 + m²)
At 100% modulation (m = 1), the theoretical maximum is 1/3, or 33.3%. This is a single-tone result for conventional AM, not a universal efficiency figure for speech transmitters. Speech has a varying envelope, and the carrier remains present even during quiet intervals, so average efficiency is commonly lower. Real transmitter DC-to-RF efficiency is a separate measure.
DSB-SC
With the carrier removed, ideal transmitted RF power is concentrated in the two sidebands. That is effectively 100% modulation-power efficiency under the narrow definition that excludes transmitter losses. The receiver must recreate a carrier with suitable frequency and phase.
Rank #3
- 30W POWER & 10M BAND: Delivers up to 30W output on the 28.000–29.700MHz 10-meter amateur band for reliable mobile communication and long-range DX operation. Ideal for overlanding, field operations, and amateur radio enthusiasts. FCC ID: T4K-AT5100
- MULTI-MODE SUPPORT: Supports FM, AM, SSB (USB/LSB), CW, and PA modes, providing flexible operation for voice communication, DX contacts, CW activities, and public address applications. Designed for licensed ham operators and emergency communication setups
- DUAL NOISE REDUCTION & ASQ: Customizable TX/RX digital noise reduction (NRC) helps reduce engine noise and cabin static. Combined with Auto Squelch (ASQ), Hi-Cut, and NB/ANL functions to deliver clearer audio during highway driving, truck operation, and off-road use
- LARGE LCD DISPLAY: Features a multi-color backlit LCD with built-in SWR, PWR, and SIG meters for real-time status monitoring. Choose from 7 display colors and 9 dimmer levels for clear visibility and personalized viewing in different lighting conditions
- ADVANCED TUNING & MONITORING: Dual Watch monitors two channels simultaneously, with CTCSS/DCS tone support for cleaner communication and 7 tuning steps from 10Hz to 1MHz for precise frequency adjustment and SSB tuning
SSB
SSB removes both the uninformative carrier and the redundant second sideband. It therefore offers the highest information-bearing power efficiency of these four for a comparable analog voice signal. The gain is paid for with sharper filtering, more complex generation, and accurate carrier reinsertion.
FM
FM’s constant envelope allows efficient nonlinear RF power amplifiers. That does not mean an FM link automatically uses less total power: RF power is distributed among sidebands, wider receive bandwidth admits more noise, and useful operation generally requires adequate carrier-to-noise ratio above the FM threshold. Compare DC amplifier efficiency, transmitted information power, received audio signal-to-noise ratio, and required field strength separately.
Receiver complexity and what operators notice
AM: simplest demodulation
An envelope detector can recover conventional AM without a carrier-recovery loop. Tuning is comparatively forgiving, and low-cost receivers are practical. The same simplicity exposes the detector to impulse noise, fading, and overmodulation. A receiver filter that is too narrow clips sidebands and reduces intelligibility.
DSB-SC: coherent detection required
A product detector multiplies the received signal by a locally generated carrier. Frequency or phase error causes output loss, distortion, or both. A suppressed carrier also cannot provide a direct tuning reference, making acquisition harder as the signal weakens.
Recommended Free Tools
SSB: precision matters
An SSB receiver selects USB or LSB and inserts a carrier with a BFO or equivalent digital oscillator. A small frequency error shifts every voice component, producing speech that sounds unnaturally high or low. Choosing the wrong sideband makes speech unintelligible. SSB transmitters use sharp filters, phasing or Weaver methods, or digital signal processing to remove the unwanted sideband.
FM: more circuitry, easier everyday use
FM receivers use an IF filter and discriminator, PLL, or digital demodulator. A limiter can remove much amplitude variation before demodulation, so the listener does not need to manage carrier phase as with SSB. Broadcast and mobile receivers commonly add de-emphasis, squelch, stereo decoding, or subcarrier processing.
Rank #4
- 40 CB Channels with Scanning: Easily scan frequencies, channels, CTCSS, and DCS to find clear signals. Access 40 CB channels to stay connected and informed during road trips, off-road adventures, and emergencies. FCC ID: 2AN62-CB606P
- Multi-Mode Support: Enjoy exceptional flexibility with AM/FM/PA support, which is ideal for communication, entertainment, and public address. Enhance functionality and sound quality by connecting to an external speaker for a richer audio experience
- User-Friendly Display: The large 2.2-inch screen is easy to read in any lighting condition. With three adjustable backlight brightness levels, you can tailor the display to your environment for optimal readability on the go
- Background Noise Reduction: Ensure clear communication with advanced noise reduction, featuring both automatic (ASQ) and manual (SQ) squelch settings. Minimize background noise for uninterrupted conversations, even in noisy environments
- Compact & Durable Design: Built with a rugged, space-saving structure for easy installation and reliable performance in any vehicle. The large, intuitive buttons ensure effortless operation, allowing you to stay focused on the road while maintaining clear communication
Noise, fading, and interference
Amplitude noise and impulse noise
AM carries information in its envelope, so atmospheric noise, ignition noise, and impulsive interference are heard directly. DSB-SC and SSB do not become noise-proof merely by suppressing the carrier; coherent detection remains necessary and in-band interference is still present.
SSB often has a practical noise advantage because its receive filter can be about half as wide as a comparable DSB filter. That admits less white noise, but it is a bandwidth benefit rather than inherent immunity.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesFM threshold and capture behavior
FM generally rejects amplitude noise after limiting and can use pre-emphasis/de-emphasis. Above threshold, it may sound much cleaner than AM. As signal strength falls below threshold, however, audio quality can collapse rapidly. Multipath causes flutter and cancellation, while the capture effect lets a stronger co-channel signal suppress a weaker one. Excessive deviation widens the signal and increases adjacent-channel interference.
Selective fading
AM, DSB-SC, and SSB can suffer distortion when propagation fades different spectral components by different amounts. SSB’s narrow bandwidth reduces exposure to some noise but does not remove selective fading. FM is also vulnerable to multipath and thermal noise; its advantage is conditional, not universal.
Where each mode fits
| Application | Why the mode fits | Typical limitation |
|---|---|---|
| Medium-wave broadcast and some aviation voice | Full-carrier AM supports simple, interoperable receivers and easy tuning | Carrier and duplicate sideband consume power; amplitude noise is audible |
| HF amateur, marine, aeronautical, emergency, and point-to-point voice | SSB conserves spectrum and transmitter power over long links | Accurate frequency control and a capable receiver are required |
| Balanced modulators, mixers, subcarriers, laboratory coherent links | DSB-SC suppresses carrier while retaining a convenient two-sideband signal | It offers no SSB bandwidth saving and needs coherent detection |
| VHF broadcast, land-mobile radio, handhelds, and amateur repeaters | FM provides robust voice/audio above threshold and permits efficient constant-envelope amplification | Channel bandwidth, multipath, capture, and threshold behavior matter |
Representative SSB and FM voice bandwidths vary by service and emission mask; an ITU report lists examples such as 11, 15, and 20 kHz FM voice emissions: ITU-R RS.2314. Amateur-band allocations and mode examples vary by jurisdiction; the ARRL band-plan page is a useful US reference: ARRL band plan.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which mode should you choose?
Choose conventional AM when simplicity and compatibility dominate
- Receivers must be inexpensive or exceptionally simple.
- An installed base or regulation already specifies full-carrier AM.
- Easy tuning is more important than minimum transmitter power.
- The service is broadcast-oriented.
Choose SSB when spectrum or transmitter power is scarce
- The link is primarily voice and point-to-point.
- Long distance, battery life, or transmitter power matters.
- The channel is narrow.
- Users can tolerate accurate tuning and more complex equipment.
Choose DSB-SC when carrier suppression is useful but both sidebands are acceptable
- A coherent receiver already exists.
- You are designing a mixer, balanced-modulator output, subcarrier, or teaching system.
- SSB’s additional filtering is not justified.
Choose FM when robust audio matters more than minimum spectrum
- Bandwidth is available.
- Amplitude noise and interference are significant.
- Good voice or music quality is important.
- Constant-envelope RF amplification is attractive.
Common misconceptions
“SSB is always twice as efficient as DSB-SC.”
SSB is approximately half the bandwidth of DSB-SC and removes its redundant sideband, but “efficiency” could mean spectrum, RF power, receiver audio SNR, or total system cost. The answer changes with the metric. FCC technical analysis discusses DSB and SSB power, bandwidth, and receiver-SNR comparisons: FCC comparison document.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Best Value
- The upgraded AT-5555N II ,its default frequency is operated in 28.000-29.700Mhz. Receiver FCC ID is T4K-AT5555NII. This 10 meter Radio is with big LCD panel, Power Output AM 60W PEP,FM 50W,SSB 60W PEP. with CTCSS/DCS Code, VOX Function,TX and RX Noise Reduction, WX weather channel and Weather Alert.Power Supply Voltage Protection.Compatible with electronic and dynamic MIC type
“FM always has greater range.”
Range depends on power, antennas, propagation, receiver noise figure, required audio quality, frequency band, terrain, and multipath. A narrow SSB link can outperform FM in weak-signal or spectrum-limited conditions.
“FM is immune to noise.”
FM rejects much amplitude noise after limiting, but thermal noise, co-channel and adjacent-channel interference, multipath, phase noise, intermodulation, and threshold collapse remain.
“DSB-SC has no carrier, so the receiver needs none.”
The transmitted waveform has no intentional carrier component, but the receiver must create or recover a local carrier reference for coherent demodulation.
“SSB cannot carry music.”
It can, but ordinary SSB is normally filtered for intelligible speech rather than high-fidelity audio. Wider audio bandwidth is possible at the cost of spectrum.
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →“AM always means full-carrier AM.”
In broad theory, DSB-SC and SSB are amplitude-modulation variants. This article uses AM as shorthand for conventional DSB-LC so the practical comparison remains unambiguous.
Quick Recap
Bottom-line engineering comparison
- AM: buys the simplest receiver and broad compatibility with wasted carrier power and poor amplitude-noise performance.
- DSB-SC: removes carrier waste but keeps both sidebands, so it saves power rather than bandwidth.
- SSB: removes carrier and one sideband, delivering the best bandwidth and information-per-watt potential for analog voice when precise synchronization is acceptable.
- FM: trades additional, deviation-dependent bandwidth for amplitude-noise rejection, clean audio above threshold, and efficient constant-envelope RF amplification.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
