Note
The Elecraft KPA500 is a compact, solid-state linear power amplifier designed for amateur radio use. Known for its rugged reliability and seamless station integration, it covers the 160-meter through 6-meter bands and delivers a conservative 500 watts of output power.
When paired with Elecraft transceivers (like the K3, K3S, or K4) using the optional KPAK3AUX cable, the integration is total. The radio and amplifier communicate bi-directionally:
Changing bands on the radio automatically changes the band on the amp, and vice-versa. The transceiver automatically remembers separate drive levels for every band depending on whether the KPA500 is in Operate or Standby, completely eliminating the risk of accidentally driving the amplifier with 100 watts.
The amplifier is often paired directly with the KAT500, Elecraft's matching 500-watt high-power automatic antenna tuner. Together with a transceiver, this combination forms an incredibly compact, automation-heavy desktop station that easily handles varying antenna impedances while maintaining a small enough footprint for portable or DXpedition use.
Features
The KPA500 utilizes a highly sophisticated "soft and hard fault" protection system. If the amplifier detects an input overdrive or a brief high-SWR condition, it doesn't just instantly drop offline and interrupt your transmission. Instead, it intelligently drops its output by 2.5 dB temporarily (a soft fault), giving the operator a chance to lower the drive power or correct the issue. If the condition is severe or prolonged, it enters a hard fault mode and safely bypasses into standby.
Intelligent, Universal Band Switching: The amplifier features an incredibly fast internal RF frequency counter. If you are using it with a non-Elecraft radio (such as a Yaesu, Icom, Kenwood, or FlexRadio) using just a basic PTT key line and an RF feed, the KPA500 will automatically sense the frequency of your first transmission or a quick "dit" and switch to the correct band instantly.
For transceivers that support it, it can also accept direct band data cabling (like BCD or serial data) to switch bands before you even press the PTT button.
Silent QSK Operation: Instead of loud, clacking mechanical relays, the KPA500 utilizes high-speed diode switching for its Transmit/Receive (T/R) system. This enables ultra-fast, completely silent QSK (full break-in) CW operation, meaning you can hear signals between your own transmitted code elements without any relay noise.
The KPA500 came in two configurations:
– Factory Assembled & Tested: Ready to plug in right out of the box.
– Modular No-Soldering Kit: A comprehensive kit where all the complex circuit boards are pre-assembled and tested at the factory. The user simply performs mechanical assembly, mounts the transformer, runs wiring harnesses, and fastens the enclosure—requiring zero soldering iron work.
Specifications
– Frequency Range: All Amateur Bands from 1.8 to 29.7 MHz and 50 to 54 MHz
– Power Output 500 watts PEP CW/SSB/Data
– Duty Cycle at 500 Watts 10 minutes key down / 5 minutes standby
– Drive Power 30 to 40 watts for 500 watts output
– Input VSWR Less than 1.5:1
– ALC Out Negative-going, adjustable
– Metering Power Output, SWR (bargraph and on the LCD display), supply voltage and current, temperature, frequency band
– PA Current 20 A maximum
– PA Voltage 60 VDC, nominal
– Heat Sink Temperature 90°C, maximum
– Key In +5V maximum, open circuit on receive, closed to ground on transmit (1 mA max.)
– Efficiency Approximately 50%
Power requirements
100 to 125 VAC or 200 to 250 VAC, 50/60 Hz, approx.1000 VA
