What changed
Amplifiers — edited Aug 31, 2026 by Unknown editor
This is the first recorded version, so every line is shown as added. Note: Imported from content/wiki
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The most common question from a new HF operator is "will an amplifier fix my signal?" Usually the
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answer is no.
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## The arithmetic
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Signal strength is logarithmic. Going from 100 W to 1,000 W is 10 dB — under two S-units. If a
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station cannot hear you at 100 W, ten times the power often still will not get you through, because
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what limits you is usually the antenna, the noise at *their* end, or propagation.
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For comparison:
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- 100 W → 200 W: 3 dB, half an S-unit. Not detectable by ear.
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- A dipole → a 3-element yagi: 5–7 dB, plus front-to-back rejection of noise. Cheaper.
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- Raising a wire from 20 to 40 feet: often more improvement than any amplifier.
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Improve the [antenna](/wiki/station/antennas) first, then the feedline, then consider power.
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## When an amplifier is the right answer
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- Heavily compromised antennas that you genuinely cannot improve (HOA, apartment, small lot).
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- Contesting and DXing where you must break a pileup against equally equipped stations.
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- Emergency and net control roles where being copyable by everyone matters.
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- Weak-signal VHF work such as [EME](/wiki/operating/weak-signal-and-scatter).
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## Types
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- **Vacuum tube** — 3-500Z, 4CX1000 and friends. Tolerant of high SWR, cheap on the used market,
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need tuning and warm-up, and hold lethal voltages inside.
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- **Solid state** — no tuning, instant on, LDMOS devices at 600–1,500 W. More expensive, and
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unforgiving of mismatch without protection circuits.
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## What comes with it
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- **Legal limit.** The US amateur limit is 1,500 W PEP output (§97.313), and the rule to use the
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minimum power necessary still applies.
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- **Power.** A kilowatt amplifier wants a 240 V circuit; check what your shack can supply.
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- **RF exposure.** More power means a mandatory station RF exposure evaluation — see the FCC's
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rules and calculators.
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- **[RFI](/wiki/station/rfi-and-noise).** Everything marginal in your house and your neighbors'
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becomes a problem at high power. Bond and filter before you transmit.
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- **Duty cycle.** [FT8](/wiki/operating/digital-modes/ft8) and RTTY are 100% duty cycle; run an
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amplifier well below its rating on those modes.