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Linear Amp Gemini HF-1K 472kHz-50MHz 1kW Solid State Linear Amplifier

  • 1kW Output
  • High Spectral Purity
  • 460KHz* to 50MHz All Bands
  • Touch Screen Full Colour LCD Display
  • Full Diode Switched QSK
  • Fully automatic Band switching
  • Network and remote capability
    • Multiple antenna outputs
    • 0dBm SMA predistortion output
    • Advanced Cooling
    • DUAL NXP BLF188XR LDMOS with Full Protection
    • 100-260V 50-60Hz power input
    • Weight 19Kg

* With external low pass filter (not supplied)

The Gemini HF-1K is a solid-state 1kW 1.8MHz – 50MHz power amplifier with additional capability at 472kHz. It uses a PAIR of BLF188XR dual-LDMOS power devices for reliability and high spectral purity and has an internal highly reliable low-noise switching power supply, in order to reduce the overall weight. The thermal design is very conservative with a large heatsink, and OFHC heatspreader. This, assisted by several fans and a sophisticated thermal management system, allowing the channel temperature of the LDMOS device to remain within limits which should ensure extended life, even with with heavy usage and yet quiet in operaiton with fans only operating when required.

A major objective of the RF design has been to significantly exceed the spurious signal generation requirements of the international approvals standard (ETS 300 783 pts 1 and 2)  for amateur radio equipment. To this end the Gemini HF-1K has more extensive filtering than is usual in HF PAs.

While LDMOS power FETs are amongst the most rugged RF power amplifier devices currently available, they are sensitive to RF overdrive. The Gemini HF-1K has both extensive monitoring to minimise the risk of damage by overdrive and a conservatively designed input circuit.

The Gemini HF kW employs full touch-screen control using a 480 x 272 pixel 108mm mm full colour TFT display. A wide range of monitoring functions can be displayed, including power output, PA drain current, VSWR and heatsink temperature. 

As with other Linear Amp UK designs, there is no provision for ALC, as this is a major cause of bad signals.

Band selection is fully automatic. The presence of valid in-band signals is detected and will initiate switching automatically to that band.

A high-speed, very low distortion, solid-state switching circuit allows very fast  (>50wpm) full break-in operation.

A single input and three selectable antenna output connectors are provided. The latter can be preset on a band by band basis.

A 0dBm (basis 100W output) SMA feedback output is provided to allow connection to transmitters with predistortion linearisation capabilities or for other monitoring functions.

The Gemini HF-1K has full network capability allowing remote operation and firmware upgrades. See links below for the remote software.

The amplifier is built in a very robust all aluminium case. A  modular assembly approach has been adopted with non-RF and high current DC interconnects being distributed as a single bus.

Operating frequencies:                               460 – 479kHz*

                                                            1.8 – 2.0MHz

                                                            3.5 – 4MHz

                                                            5.0 – 5.5MHz

                                                            7.0 – 7.3MHz

                                                            10.1 – 10.2MHz

                                                            14.0 – 14.4MHz

                                                            18.0 – 18.2MHz

                                                            21.0  - 21.5MHz

                                                            24.8 – 25.0MHz

                                                            28.0 – 29.7MHz

                                                            50.0 – 54.0MHz

*when used with an external accessory low pass filter unit (not supplied)


Power output:                                     >1 kW at 1dB gain compression (200W+ on 460-479KHz)

Power input:                                        5, 10, 50W customer specified (50W standard)

3rd order IMD distortion:                       better than -30dB at 1kW

11th order IMD distortion:                      better than -70dB at 1kW

Harmonic suppression:                          better than 70dB (all harmonic products)

Input VSWR:                                        better than 1.5:1

Load VSWR tolerance:                            <1.5:1 for best performance with  2.5:1 high VSWR trip.

Typical 2-tone test plots at 1kW pep are shown below - click on the image for a larger pdf version.