(tr) µSDX 5-Band QRP SDR Multimode HF Transceiver


The super-compact fully assembled (tr)µSDX 5-Band QRP class-E driven multimode SDR HF transceiver created by DL2MAN and PE2NNZ puts the world in the palm of your hand! Despite its small size, it covers 5 HF amateur bands 80, 60, 40, 30 and 20 meters and operates in LSB, USB, CW and DATA modes.

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(tr) µSDX 5-Band QRP SDR Multimode HF Transceiver

This transceiver can be used to make QRP SSB and CW contacts, or (in combination with a PC) can be used for digital modes such as PSK31, FT8, JS8, FT4, RTTY, FSK, JT4, JT9, JT65, MFSK, WSPR and so on. It has up to 5 Watts PEP SSB output power.

It is supplied with an OLED Display, onboard microphone, and tiny onboard speaker and for improvised QSO onboard PTT Key can be used as an emergency CW Key. Further on, the (tr) µSDX transceiver has a micro USB CAT and programming interface, and while it produces typically 5W @ 13.8V Power Supply, it does 0.5W output from a 5V USB supply alone.

Typically it draws 80 mA on RX (with MS5351 – less with Si5351) and 500 mA on TX @13.8V and has typical 85% PA Efficiency. It is supplied with OnBoard SWR Bridge and Voltage / Current measurement hardware, to help in tuning and operation.


(tr) µSDX 5-Band QRP SDR Multimode HF Transceiver

The (tr) µSDX transceiver has been created to try out what can be achieved with minimal hardware while moving complexity towards the software; here the approach followed is to simplify the design where possible while keeping a reasonable performance.

The result is a cheap, easy-to-use, versatile QRP SSB / CW transceiver that actually is quite suitable for making QSOs (even in contest situations).

The (tr) µSDX transceiver’s unique form factor allows you to operate from anywhere. With a whip antenna, you can even operate it hand-held. Press the PTT button to transmit and talk straight to the built-in microphone while holding the radio in your hand.


Full-Featured, yet easy to use the (tr) µSDX 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 an OLED display, so all operating information is available at a glance. Free firmware upgrades are available via the internet.


General Overview
(tr) µSDX 5-Band QRP SDR Multimode HF Transceiver


Pin-Out of External Connections
(tr) µSDX 5-Band QRP SDR Multimode HF Transceiver


Main Features and Specifications:

  • OLED Display.
  • Built-in Speaker.
  • Built-in Microphone and PTT.
  • PA Stage Efficiency: 80%.
  • BNC Antenna Socket.
  • 13.8V Power Supply Provides up to 5 Watts PEP SSB Output Power.
  • Bands: 80, 60, 40, 30, and 20 m.
  • Modes: USB, LSB, CW, Digital + AM, FM.
  • DSP Filter: 3000, 2400, 1800, 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.
  • 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 800 kbits/s I2C) and the amplitude of the PA (through PWM of the PA key-shaping circuit).
  • Attenuators: 0 dB, -13 dB, -20 dB, -33 dB, -40 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.
  • CAT support (Kenwood TS-480 subset).
  • Compact Size: 90 x 60 x 30 mm.


3b (tr) µSDX Firmware                                      4 (tr) µSDX Manual

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