Elecraft KPA500
$$$$·
| Frequency | 1.8-29.7 MHz (all amateur bands, 160-10 m), 50-54 MHz (6 m) |
| Bands | 160m, 80m, 40m, 30m, 20m, 17m, 15m, 12m, 10m, 6m |
| TX power | 500 W (500 W PEP output on CW, SSB and data from 30 to 40 W of drive; Elecraft rates it as '500+ watts.' A pair of VRF2933 RF power MOSFETs runs at 60 VDC nominal (20 A maximum), about 50% efficient. Rated duty cycle at full output is 10 minutes key-down then 5 minutes standby, so sustained high-duty digital operation runs warmer. Soft faults from input overdrive or high SWR cut output about 2.5 dB temporarily and recover automatically; severe faults switch the amplifier to standby.) |
| Modes | CW, SSB, Data (FT8/RTTY and similar), AM/FM (within the 500 W PEP rating and duty cycle) |
| Weight | 11.8 kg (26 lb) |
| Year | 2011 |
| rf input | SO-239, 50 ohm (drive from the transceiver via PL-259 coax); 30-40 W for full output |
| rf output | SO-239, 50 ohm, single antenna output; no internal antenna tuner |
| pa key | RCA phono PA KEY input: grounded on transmit (sinks up to 1 mA); if the radio's key line is not a contact closure it must sit at +4 to +16 VDC on receive |
| alc out | RCA phono ALC output: negative-going, adjustable, 0 to -12 VDC |
| rs232 xcvr | RS-232 (XCVR) DE-9 serial: band/frequency data from other transceivers (cannot update firmware) |
| rs232 pc | RS-232 (PC) DE-9 serial: KPA500 Utility and firmware updates; Elecraft supplies a USB-to-RS232 (KUSB) cable for modern PCs |
| aux k3 | AUX DE-15 (15-pin) for the KPAK3AUX cable: Enhanced Mode with the K3/K3S (band data, keying, operate/standby sensing) |
| ground | GND thumbscrew for station ground |
| ac mains | IEC AC inlet, 100-125 VAC or 200-250 VAC, 50/60 Hz, approx. 1000 VA; voltage changed at the fuse block without opening the cabinet |
| power req | AC mains only: 100-125 VAC or 200-250 VAC, 50/60 Hz, approximately 1000 VA, from a built-in low-noise linear supply on a toroidal transformer. Runs on a standard 120 V household circuit; 240 V is supported. Voltage is switched at the fuse block (changing fuses and reinserting the block) without opening the cabinet. |
Makes a full 500 watts (Elecraft rates it 500+) from only 30 to 40 watts of drive, so any 100 W radio drives it easily and even the KX3 and KX2 reach 180 to 220 watts. RF-sensing band switching follows almost any transceiver with just keying and RF connected, and the built-in linear supply keeps it to one box and one mains cord. PIN-diode switching is silent and supports QSK, and the unit is the same size as the K3S with a full metering display.
It is a 500-watt amplifier rather than a kilowatt, and it has no built-in antenna tuner, so automatic matching means buying the KAT500 alongside it. The rated duty cycle at full output is 10 minutes key-down then 5 minutes standby, which matters for long high-duty digital runs. The current factory-assembled price is high compared with imported 500-watt amplifiers.
The KPA500 is a compact 500-watt solid-state linear amplifier covering 160 through 10 meters plus 6 meters. It is built to match the Elecraft K-line but works with most transceivers through RF-sensing band switching, needs only 30 to 40 watts of drive, runs from a built-in linear supply, and uses silent PIN-diode switching. It has no internal tuner, so operators who want automatic matching add the KAT500, while those who need full legal-limit power step up to the KPA1500.
The Elecraft KPA500 is a 500-watt solid-state linear amplifier covering all amateur bands from 1.8 to 29.7 MHz plus the 6-meter band at 50 to 54 MHz. Its output stage is a pair of VRF2933 RF power MOSFETs running at 60 volts, and it needs only 30 to 40 watts of drive for full output, so any 100-watt transceiver drives it with room to spare. A built-in low-noise linear power supply on a toroidal transformer runs the amplifier from 100-125 or 200-250 VAC, and the mains voltage is changed at the fuse block without opening the cabinet.
The amplifier is designed to work with almost any radio. It senses the transmitted RF and uses an internal frequency counter to switch to the correct band automatically, so only keying and RF connections are required; an RCA PA-key input and a negative-going RCA ALC output handle keying and drive control. It uses silent PIN-diode transmit/receive switching that supports full break-in, and protection circuitry reduces output about 2.5 dB on input overdrive or high SWR and recovers on its own, dropping to standby only on severe faults. An alphanumeric display and LED bar graphs show power, SWR, voltage, current, temperature and band.
The KPA500 is the same size as the K3S and forms the amplifier of Elecraft's K-line. Over the KPAK3AUX cable (a DE-15 connection) it runs in Enhanced Mode with the K3/K3S, sharing band data and keying and letting the radio set two per-band drive levels. It has a single SO-239 antenna output and no internal tuner, so it is usually paired with the KAT500 autotuner. The smaller KX3 drives it to about 220 watts and the KX2 to about 180 watts; operators who need full legal-limit power use the KPA1500 instead.