19 November 2021

Looking for clean SS HF PA w/QSK - part 8 (KM3KM Mercury IIIS LDMOS kit)


Hi all,

here is another way how to get the SSPA for HF. The question is - if it meets all of our requirements and needed features...
In that case it is a bit special stuff as it is sold as the kit which has to be assembled and tested before using it in the hamshack.

As you know my preview parts talked about:
ACOM 1200S
LINEAR Amp Gemini HF-1K

Azden AZR-1000

Elecraft KPA1500

KM3KM Mercury IIIS LDMOS kit

This solid state HF amplifier uses a single LDMOS for fully automatic operation from 160m to 6M making 1200W with input power between 50 and 90W depending on your ALC setting. Protected against antenna SWR over 2 to 1 and also against excessive input power. Built-in power supply for 120 or 240 VAC without changing taps in the transformer, just changing the power cable plug.

Fans work silent and color front panel display. Output to three antennas selectable in the display with operator finger.
This is a kit that you put together at home but assembly is very easy to do.

• Solid state amplifier (BLF189XRA)
• 1.8 - 54 MHz
• All Protections
• RF Band Decode
• FWD / SWR Meter
• Output Digi 700 Watts
• Output SSB/CW 1200 Watts
• Antenna Selector Switch
• 7 Inch Touch Color Screen
• Di Voltage / Di Current Meter

• Integrated Power Supply 120-240v

• W12 x L13.5 x H5.5 inch

• Weight 26 pounds


Maintains linearity under full output power (1200watts). 

Low harmonic content (below -43dBc on HF & -65dBc on VHF bands) thanks to an efficient Chebyshev filter. 

Fast and effective protection systems maintain the amplifier’s safety from operational damage.
Compact linear amplifier with 1200 watts SSB/CW & 700 watts DIGI-MODE of output power on all amateur bands from 1.8 to 54MHz (<800watts 50 to 54MHz) 

Auto sensing power supply from 120 to 240VAC.

There is nothing said about the T/R switching but it looks like relay T/R switching is used so no QSK unfortunately. 

The powerful PSU is built-in. Also extremely low noise fan cooling system is designed for that amp so you will not feel like sitting on the tarmac waiting for the jet to take off. (compare to KPA1500 or Palstar LA-1K or the SPE 1.5K amps...)

No ATU unit built-in just three antennas switch installed. So compare to other SSPA like B26-PA RF2K-S there seems to be disadvantage.

This amp provides a COOL SOLID 1 KW output on CW. It is the best bang for the buck on the market. This amp is high tech simplicity. Everything is modular and easily replaced if repair is needed which is not likely. Running 1 KW all the time leaves 200 watts of head room and because you are running near max the amp is more efficient and produces less heat than other amps designed to run at 1500 watts when you run them at 1 KW.

Five stars overall rating on eHam from currently 48 reviews is really promising... 

KM3KM website:

Assembly manual:

Operating manual:

73 - Petr, OK1RP
"auf die Dauer hilft nur Power" (Erich, HB9FIH)

16 November 2021

Looking for clean SS HF PA w/QSK - part 7 (B26-PA RF2K-S)


Hi all,

when I talked to Reinhard, DH3NAB about their latest version of the SSPA (www.rf-kit.de) he advised me to wait until their new version (with PIN diodes switching, reaches <5ms switching time) will be launched. The year was 2019.

As you know my preview parts talked about:
ACOM 1200S
LINEAR Amp Gemini HF-1K

Azden AZR-1000

Elecraft KPA1500

Here is what the RF-Kit offers these days...

The new version B26-PA RF2K-S 

The RF-Kit B26-PA RF2K-S comes at first as a kit. In this case Kit does not mean that you get 100 plastic bags with individual parts, you need to assemble and solder boards, drill housing parts or connect the PA.

The PA kit is always delivered as an almost finished device. To make the kit an operational device, it is necessary to obtain a Raspberry® Pi 4 - 2GB and a power cord. All other necessary parts such as 1 x coaxial cable, power plug, USB cable, HDMI cable and micro SD card are included in the scope of delivery.

To finish the kit the Raspberry has to be installed (spacers are already mounted for this purpose and also the necessary fixing screws are included). Connect the supplied USB and HDMI cables, solder in the coaxial cable. Thereafter, commissioning takes place with the necessary calibration / setting.

No special tools are necessary for all this work. Screwdrivers, soldering iron, DVM, Ampere meter / current clamp and RF power meter are everything.

If you have any questions, please contact RF-Kit and a very large community at Groups.io with more than 1,300 members. A current version of the operating instructions is also available there at any time.

A micro SD card is included. Since the PA has a LAN port for possible "remote operation", the operating software can be downloaded from the Internet, and always updated with the availability of a new version.

General Features:

  • Frequency Range: 1.8-30 MHz and 50-54.2 MHz

  • RF-Output: 1500 Watts - 6m: 1100 Watts (with headroom)

  • Exciter Drive Level: 50 Watts on all bands 

  • Efficiency: Up to 70% varies by band

  • TX/RX switching: 1mS PIN-Diode switching

  • Internal Automatic Antenna Tuner ( unlimited Memories )

  • 1X TRX and 4x Antennas

  • Excellent signal quality

  • Very silent operation due to speed controlled low noise fans

  • Dual LDMOS devices rated at 3400 Watts

  • 7-inch Color Touch Screen

  • Multiple user selectable displays

  • -55 dB output for Predistortion

  • Auto RF Sens Band Selection

  • TCI Interface for SunSDR

  • YAESU® Band Data Interface

  • YAESU BCD Band DATA output for external devices

  • CAT Connectivity through USB

  • CAT through IP ( UDP )

  • LAN Connectivity (full Remote operation)

  • Wi-Fi Connectivity ( Host or Client mode )

  • Quiet internal PSU 90-290 VAC

  • 800W output 110 VAC;  full power at 230 VAC

  • Power Meter from 1 W through 2 KW

  • Sleep mode for low power consumption

  • Software Update via Internet

  • Full Remote Internet operation via PC, Tablet or cell phone
    Supports platforms such Apple® IOS, Android®, Linux® and MS Windows®

  • FCC approval for ready build kit's in US

  • External Power/ON applying +12V

  • Dimensions HWD: 7,4 x 12,2 x 16,7 inch. / 19 x 31 x 42,5 cm

  • Weight: 35,2 lbs / 16 Kg

  • FCC approval for ready build kit's in USA

   Join the RF2K user group at Groups.io

All of these sounds really promising and frankly speaking it looks like one of the best SSPA on the market in its category! 

You can order it directly from Germany or from their official distributors in USA.

As I had no chance to test it yet, I can only highlight that:

- ATU is built-in
- PSU unit is built-in
- PIN diodes with switching time <2ms is built-in
- 4 antenna ports are built-in 
- low noise fans used (no annoying high level "jet" noise expected)

The questions remains:

- amplifier reliability in 48hrs contest at full power and run mode
- related to preview point the cooling efficiency and operating temp
- protections functionality against badas or tired operator's mistakes

What I am missing at the first look in...?

- 6 antenna ports implementation to cover all basic ham bands

RF-KIT website:


Assembly manual:

User manual:

Controller upgrade manual:

73 - Petr, OK1RP
"auf die Dauer hilft nur Power" (Erich, HB9FIH)