Description:
uSDR is optimized and modified based on the open source work uSDX/QCX-SSB.

uSDX/QCX-SSB GitHub: https://github.com/threeme3/QCX-SSB/tree/feature-rx-improved

This is a shortwave QRP SSB/CW transceiver. The ultra-small size makes it easy to carry for outdoor use. It adopts 1602N LCD screen, built-in speakers. Support to connect to PC and use FT8, JS8, FT4 and other digital mode software control, support CW automatic decoding.

Features:
- 8 band coverage 80m/60m/40m/30m/20m/17m/15m/10m
- Excellent PCB layout design in line with high-frequency circuit design principles to ensure excellent performance
- Can reach 3-5W power in 8 bands and reserve TO-220 package pads required for upgrades
- High emission efficiency, 80m/60m/40m/30m/20m efficiency is higher than 85%, 17m/15m efficiency is higher than 80%, 10m efficiency is higher than 70%
- High-precision for KDS brand TCXO, frequency accuracy is better than 1PPM, frequency stability is better than 0.5PPM
- Independent core board and RF board to avoid own signal interference.
- Ultra-small size: 83 x 38 x 124mm(excluding protruding parts)
- Rich interfaces (CAT, PTT OUT, MIC/KEY, K-head microphone)
- All LPF parts use 100V C0G/NP0 capacitors
- Use original genuine Omron magnetic latching relay
- Use original genuine LM4562 or LM833 op amp chip
- Built-in speaker with cavity
- BNC antenna interface

Function List:
- Simple, fun and versatile QRP SSB HF transceiver with embedded DSP and SDR functions
- EER Class-E driven SSB transmit-stage
- Approximately 5W PEP SSB output from 13.8V supply
- All-Mode support: USB, LSB, CW, AM, FM
- DSP filters: 4000, 2500, 1700, 500, 200, 100, 50 Hz passband
- DSP features: Automatic Gain Control (AGC), Noise-reduction (NR), Voice-triggered Xmit (VOX), RX Attenuators (ATT), TX noise gate, TX drive control, Volume control, dBm/S-meter
- SSB opposite side-band/carrier suppression transmit: better than -45dBc, IMD3 (two-tone) -33dBc, Receive: better than -50dBc
- Multiband support, continuously tunable through bands 160m-10m (and from 20kHz..99MHz with loss in performance)
- Open source firmware, built with IDE for Arduino; allows experimentation, new features can be added, contributions can be shared via 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
- Simple to install modification with 8 component changes and 8 wires
- Lightweight and low-cost transceiver design: because of the EER-transmitter class-E stage it is highly power-efficient (no bulky heatsinks required), and has a simple design (no complex balanced linear power amplifier required)
- 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)
- Fully digital and software-based SDR receiver-stages (optionally): samples I/Q (complex) signal from Quadrature Sampling Detector digital mixer, and performs a 90-degree phase-shift mathematically in software (Hilbert-transform) and cancels out one side-band by adding them
- Three independent switchable analog front-end receiver attenuators (0dB, -13dB, -20dB, -33dB, -53dB, -60dB, -73dB)
- Receiver Noise level MDS: -135 dBm at 28MHz (in 200Hz BW)
- Receiver Front-end selectivity: steep -45dB/decade roll-off +/-2kHz from tuned-frequency
- Blocking dynamic range: 20kHz offset 123dB, 2kHz offset 78dB
- CW decoder, Straight/Iambic-A/B keyer
- VFO A/B + RIT and Split, and corresponding relay band-filter switching via I2C
- CAT support (TS480 subset)