µSDX Plus V2 QRP SDR HF Transceiver


The revolutionary µSDX Plus V2 QRP class-E driven SDR HF transceiver puts the world in the palm of your hand! Despite its small size, it covers 9 HF amateur bands from 80 to 10 meters and operates in SSB, CW and DATA modes.


Available options and accessories allow the µSDX Plus V2 QRP SDR HF transceiver to be tailored to your needs, including the optional CW Keyer, Handheld Microphone, Data mode and CAT Control Interface, 100W Power Amplifier, External ATU, and Low Pass Filters Unit. Whether you’re bagging a new peak on a SOTA outing, pounding out QSOs on Field Day, activating a new POTA park or working rare DX from the comfort of your home station, your µSDX Plus V2 QRP SDR HF transceiver will provide the features and performance you need.

This transceiver can be used to make QRP SSB and CW contacts, or (in combination with a PC) can be used for the digital modes such as PSK31, FT8, JS8, FT4, RTTY, FSK, JT4, JT9, JT65, MFSK, WSPR and so on. It can be fully continuously tuned through 80 m – 10 m bands in the LSB and USB modes. With a 2400 Hz bandwidth it has up to 3 – 5 Watts PEP SSB output and features a software-based full Break-In VOX for fast RX/TX switching in voice and digital operations.

The SSB transmit stage is implemented entirely in a digital and software-based manner: at the heart, the ATMEGA328P is sampling the input audio and reconstructing an SSB signal by controlling the SI5351 PLL phase (through tiny frequency changes over 800kbit/s I2C) and controlling the PA Power (through PWM on the key-shaping circuit). 

In this way a highly power-efficient class-E driven SSB signal can be realized; a PWM-driven class-E design keeps the SSB transceiver simple, tiny, cool, power-efficient and low-cost (ie. no need for power-inefficient and complex linear amplifier with bulky heat-sink as often is seen in SSB transceivers).

For the receiver, most parts are implemented in the digital manner (software): the ATMEGA328P is implementing a 90-degree phase shift circuit, the (CW/SSB) filter circuit and the audio amplifier circuit (now a class-D amplifier). This has simplified the µSDX circuit a lot, and there are a number of advantages and features (compared to an analogue approach): there is no longer a need for an I/Q alignment procedure due to the very accurate 90-degree Hilbert phase shifter, and there are now adjustable IF DSP filters for CW and SSB, and there is an AGC and there is a noise-reducing DSP signal conditioning function and there are three independent built-in attenuators in the analogue front-end which helps to utilize the full dynamic range.

The speaker is directly connected and driven by the ATMEGA. A digital mixer with a narrow low-pass window (2 kHz), steep roll-off (-45 dB/decade) combined with an oversampling and decimating ADC are responsible for a processing gain, dynamic range and alias rejection sufficient to handle weak and strong signal conditions (e.g. contests or listening on 40 m just next to broadcasting band).

The µSDX Plus V2 SDR HF transceiver’s unique form-factor allows you to operate from anywhere. With a whip antenna, you can even operate it hand-held. For extreme portability, you can use the optional compact portable antenna, external wide-range ATU, small 12V external battery, and optional CW keyer.

The µSDX Plus V2 SDR HF transceiver’s unique form-factor allows you to operate from anywhere. With a whip antenna, you can even operate it hand-held. Press the bottom red PTT button to transmit and talk straight to the built-in microphone while holding the radio in your hand. For extreme portability, you can use the optional external wide-range ATU, built-in 12V battery, optional CW keyer or handheld microphone.

Transmit efficiency is also excellent, further improving battery life. Full-Featured, yet easy to use the µSDX Plus V2 QRP SDR HF transceiver features a compact design with all controls optimized for convenient use. You simply dig through simple menus to set the power level, adjust the keyer speed, or change filter settings. The radio has the 1602 liquid-crystal display, so all operating information is available at a glance. Free firmware upgrades are available via the internet.

  • LCD-1602 Display
  • Built-in 12V Lithium Ion Battery
  • Built-in Speaker
  • Built-in CW Decoder
  • IRF MOSFET Power Transistors
  • BNC Antenna Socket
  • 13.8V Power Supply Provides up to 3 – 5 Watts PEP SSB Output Power
  • Bands: 80, 60, 40, 30, 20, 17, 15, 12 and 10 m
  • Modes: USB, LSB, CW, Digital
  • DSP Filter: 4000, 2500, 1700, 500, 200, 100, 50 Hz
  • Functions: Automatic Gain Control (AGC), Noise Reduction (NR), Voice Trigger, Voice Trigger Xmit (VOX), RX Attenuator (ATT), TX Noise Gate, TX Driver Control, Volume Control, dBm/S-meter
  • SSB Reverse Sideband/Carrier Suppression Transmission: better than -45 dBc, IMD3 (two tones) -33 dBc, reception: better than -50 dBc
  • Open source firmware, built in for Arduino IDE; allows experimentation, can add new functions, can share contributions through Github, software complexity: 2000 lines of code
  • Software-based VOX that can be used as fast Full Break-In (QSK and semi-QSK operation) or assist in RX/TX switching for operating digital modes (no CAT or PTT interface required), external PTT output/PA control with TX-delay
  • Fully digital and software-based SSB transmit-stage: samples microphone-input and reconstruct a SSB-signal by controlling the phase of the SI5351 PLL (through tiny frequency changes over 800kbits/s I2C) and the amplitude of the PA (through PWM of the PA key-shaping circuit)
  • Three independent switchable analog front-end receiver attenuators (0 dB, -13 dB, -20 dB, -33 dB, -53 dB, -60 dB, -73 dB)
  • Receiver noise level MDS: -135 dBm (200 Hz BW) at 28 MHz
  • Receiver front-end selectivity: steep tuning frequency -45 dB / ten times roll-off +/- 2 kHz
  • Blocking dynamic range: 20 kHz offset 123 dB, 2 kHz offset 78 dB
  • CW decoder, straight/Iambic-A/B keyer
  • VFO A/B + RIT and and Split, and switch the corresponding relay band filter through I2C
  • CAT support (Kenwood TS-480 subset), you can stream audio, press keys, and display text through CAT
  • Compact Size: 83 x 38 x 124 mm
  • Charge: Charging Port for the Built-in Lithium Battery
  • ON/OFF Button: to Power On or Shut Down the Transceiver
  • DC 13.8V/3A: External Power Supply Port
  • KEY/MIC: Automatic CW Key Connection (A, B, Single Key) / External Microphone 
  • CAT/PTT: Serial Communication Port (CAT Control Commands Compatible with Kenwood TS-480) / External Power Amplifier, PTT Signal
  • HP: Headphones (when connected mutes the internal speaker)