Best HF amplifiers

An amplifier is the most misunderstood purchase in amateur radio, because power and perceived signal strength are related logarithmically and nobody finds that intuitive. Going from 100 W to 400 W is four times the power and one S-unit on the other operator's meter. Going from 100 W to 1000 W, a tenfold increase, is about 10 dB, which is under two S-units.

Meanwhile, getting a wire antenna from 20 ft to 40 ft can easily be worth several decibels on a DX path, and fixing a lossy feedline can hand back 3 dB you were already paying for. Both cost far less than an amplifier.

None of that means amplifiers are pointless. It means they are the last upgrade rather than the first. Everything here is researched from published specifications and verified owner reports rather than from testing we have not done.

The arithmetic, stated plainly

What to fix before buying an amplifier

1. Antenna height. Raising a dipole from a quarter wavelength to a half wavelength up changes the takeoff angle substantially, and on DX paths that is worth more than a power increase. Check with the antenna height calculator.
2. Feedline loss. If you are losing 3 dB in coax you are throwing away half your existing power, and fixing it is cheaper than buying more. Run the coax loss calculator.
3. Antenna type. A resonant full-size antenna against a short loaded one is often several decibels, in both directions.
4. Receive noise. An amplifier does nothing whatsoever for your ability to hear. If you cannot hear them, more transmit power is the wrong tool entirely.
5. Only then consider an amplifier.

What an amplifier demands from the rest of the station

• Power. A 500 W amplifier at 12 V draws upward of 60 A, well beyond a normal station supply. Many HF amplifiers run from mains directly for this reason.
• Feedline and connectors rated for the power. PL-259 is fine at HF legal limit; the coax must be too.
• An antenna and tuner rated for the power. A tuner rated at 100 W will fail, sometimes spectacularly.
• A fresh RF exposure evaluation. This is not optional. Your compliance distance scales with power, and the FCC requires every station to have an evaluation on record. Re-run the RF exposure calculator.
• Attention to common-mode current. More power makes every RFI problem in the house louder, and a feedline choke goes from advisable to necessary.

When an amplifier is genuinely the right answer

There are real cases. If you are already running the best antenna your property allows on good feedline and still losing marginal DX contacts, more power is the remaining variable. Contesters and DX chasers competing into pileups are fighting other stations for a slot and power decides who gets heard. And if a physically small antenna is your only option because of restrictions or space, power partially compensates for what the antenna cannot do.

What is not a good case: being unable to hear the station you are calling, general dissatisfaction with a station whose antenna has never been optimised, or the belief that an amplifier will fix a high SWR. It will not, and driving an amplifier into a bad match is how amplifiers die.