Note
The Elecraft KPA1500 is a compact, solid-state linear amplifier delivering a full 1500 watts of power across all amateur bands from 1.8 to 54 MHz.
Two-Enclosure Layout: To maximize station layout flexibility and minimize operating desk space, the KPA1500 splits the system into two separate units: the RF Deck and an external Power Supply. Both units share identical enclosure dimensions.
Quiet Cooling: Because the power supply can be placed completely out of reach (such as under a desk), its fans run continuously when the amp is powered, isolating that sound from the operating position. The RF Deck’s internal fans engage and scale up speed automatically based on temperature.
Power Output: 1,500 Watts PEP (Peak Envelope Power) for CW, SSB, and Data modes.
Duty Cycle: 100% ICAS for heavy-duty modulation modes such as FM, RTTY, FT8, and JT65. Key-down time limits are 5 minutes maximum for 1.8–30 MHz, and 50 seconds maximum for 50 MHz.
Drive Power: Typically requires only 50 to 60 watts of drive power to reach the full 1,500W output.
Efficiency: Approximately 50% (varying slightly by frequency band).
T/R Switching: Transmit-Receive switching utilizes PIN diodes, making the operation entirely fast and noise-free (silent break-in).
The KPA1500 features a built-in ATU based on an "L" matching network consisting of 8 capacitors and 7 inductors switched via high-speed relays.
Matching Range: It can successfully match loads with an SWR up to 3:1 at the full 1,500W output. At reduced power (e.g., 500W–750W), it can handle wider mismatches—up to 10:1 SWR on the HF bands.
Tuning Memory: The ATU splits the 1.8 to 54.2 MHz operating spectrum into narrower frequency segments (ranging from 10 kHz steps on 160m to 200 kHz steps on 6m). Storing successful "Full Search Tune" data allows the amplifier to instantly recall matching solutions as you change frequencies.
Standby Mode Pass-Through: The ATU remains completely accessible when the amplifier is switched to Standby (STBY) mode, allowing a "barefoot" transceiver to utilize the tuner.
Instantaneous Band Switching: It features automatic RF-based band switching to safely sense and follow frequency changes upon transmission.
Enhanced Mode (Frequency Tracking): By connecting dedicated control cabling (via the DE-15 AUX port or 3.5mm XCVR SERIAL jack), the KPA1500 supports digital communication protocols (like Icom CI-V, Kenwood, Yaesu BCD, FlexRadio) to track the radio's frequency without needing to transmit first.
Elecraft K-Line Integration: When paired via the KPAK3AUX cable with an Elecraft K3 or K3S transceiver, integration is seamless and bidirectional. Tapping band switches on the amplifier shifts the radio's band, and the transceiver dynamically selects appropriate per-band drive levels depending on whether the amplifier is online (OPER) or offline (STBY).
The front panel provides a clear layout for configuration, including an alphanumeric LCD and dual LED bargraphs displaying real-time Forward Power and SWR. The amplifier protects itself through two tiers of fault conditions:
Soft Faults: Triggered by minor issues like mild overdrive or transient high reflected power. The KPA1500 activates an internal 3 dB attenuator in the drive path, blinks the `OVR` LED, and flashes a message on the LCD. It drops back to normal operation automatically once drive power is reduced.
Hard Faults: Triggered by severe conditions like severe SWR mismatches, component failures, or dangerous high-voltage out-of-range limits. The amplifier drops offline immediately into Standby (STBY) mode, illuminates the `FAULT` LED, and sounds a warning tone until manually cleared or reset.
Additionally, the RF Deck includes a dedicated internal low-level directional coupler output (-60 dBm) on the rear panel specifically to support transceivers capable of closed-loop pre-distortion (such as PureSignal) to reduce intermodulation distortion (IMD).
Specifications
– Frequency Range: All Amateur bands from 1.8 to 29.7 MHz and 50 to 54.2 MHz.
– Power Output: 1500 W PEP CW/SSB/Data.
– Duty Cycle at 1500 Watts:
100% ICAS for 100% duty cycle modulation modes (FM, RTTY, FT8, JT65, etc.);
1.8-30 MHz: Maximum 5 minutes key down / Minimum 5 minutes receive (after 5 minute TX)
50 MHz: Maximum 50 seconds key down / Minimum 50 seconds receive
– Drive Power: 50-60 W, typical, for 1500 W 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.
– Heat Sink Temperature: 110ºC, maximum.
– Key In (Transmit Enable): +5V maximum, open circuit on receive, closed to ground on transmit (5 mA max.).
– Efficiency: Approximately 50%. Efficiency varies by band.
– Antenna Tuning Unit Matching Range and Power Limits:
1.8 – 2 MHz: 1500 W into 16 to 150 Ω (3:1 SWR)
750 W into 12 to 200 Ω (4:1 SWR)
3 – 30 MHz: 1500 W into 16 to 150 Ω (3:1 SWR)
750 W into 5 to 500 Ω (10:1 SWR)
30-54 MHz: 1500 W into 16 to 150 Ω (3:1 SWR)
500 W into 10 to 250 Ω (5:1 SWR)
Note: Matching specified to a 1.0:1 to 1.6:1 output SWR.
– Autotune Power Range: 10 W - 1500 W (For better matching accuracy, tune with >20 W).
Power requirements
200 to 250 VAC, 50/60 Hz, 20 amps max.
