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The Gemini HF-1K is a solid-state 1kW 1.8MHz – 50MHz power amplifier with additionalcapability at 472kHz. It uses a PAIR of dual-LDMOS BLF188XR power devices for reliability, and has full high speed QSK capability using a diode switching circuit.
The HF-1K is a Linear amplifier so suitable for all modes of operation – SSB/CW/RTTY/AM/FM/Data etc.
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.
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-1K employs full touch-screen control using a 480 x 272 pixel 108mm mm full colour TFT display. A wide range of monitoring functions are displayed, including power output, PA drain current, VSWR, band and antenna in use 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 fullly automatic – no CAT needed. The presence of valid in-band signals is detected and will initiate switching automatically to that band. The amplifier will not transmit if out of band,
A high-speed, very low distortion, solid-state switching circuit will allows silent fast full break-in operation (QSK) to over 50wpm.
A single input and three selectable antenna output connectors are provided. The latter can be preset on a band by band basis.
A rear panel 0dBm SMA output is provided to allow connection to transmitters with linearisation capabilities. This is 0dBm at 100w output or 10dBm at 1kW output and is optimised as a predistortion low level ouput for Anan and other SDR transceivers. It can, of course, be used for any other time of low level signal monitoring applications such as spectrum analysis.
The Gemini HF-1K has full network capability allowing remote operation and future firmware upgrades.
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, 10W, 50W, customer specified (50W supplied as 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 (we recommend use of an external ATU above 1.5:1)
Operating Manuals, Remote Software and Firmware updates are available from http://linearamp.co.uk/ghf_software.html