WA3TFS SDR Upverter Design

Features

SDR up-converter/receiver shifts HF (0-30 MHz) frequencies up by 100 MHz. Used to listen to HF frequencies on an inexpensive RTL-SDR module.

• $55
  • Purchased at W3PIE hamfest
  • Can be ordered as PCB, Kit, or assembled
• SBL-1 Level 7 mixer
• 100 MHz can oscillator
• Low pass filter
  • 35 MHz
• 1 kHz to 1.7 GHz SDR Receiver - WA3TFS Design
  • QST Article
  • SDR wiring diagram
  • Parts List
  • Layout

Schematic

Pass Filter

• 9 turns on FT37-2 = 0.3 uH

• LTSpice Simulation
  • 1-100 MHz

• LTSpice Simulation
  • 1MHz-1GHz

Software

• RTL-SDR
• HDSDR - Easier to use
• SDR Sharp - Crashier

Build

• Nice silver mica caps for the band pass filter
  • My kit was missing the center cap of the band pass filter (150 pF)
  • I used a junk box ceramic disc cap
• 30pF cap installed in J_A to J_B marked 300
• Build was too tough due to very small pads on the PCB
  • Particularly tough to solder ground pads
  • Pad shapes were not round so less area to set soldering iron
• Is LO drive more than 7 dBm?
• Pin 1 orientations on the mixer and oscillator "backwards" from other board legends
  • Pin 1 shown in red circle

RTL-SDR

• RTL-SDR DONGLES (RTL2832U) - rtl-sdr.com site
  • RTL-SDR Quick Start Guide
• <1 PPM temperature compensated oscillator (TCXO)
  • Accurate tuning and almost zero temperature drift (2 PPM max. initial offset, 0.5-1 PPM temperature drift)
  • SMA female antenna port
  • Generic dongles use the less common MCX or PAL antenna ports
  • SMA is more common, so more adapters and antennas are available for it
  • It is also more durable and has lower RF insertion losses
• 4.5V USB powered bias tee
  • This allows the RTL-SDR to power low noise amplifiers (like the LNA4ALL, HABAMP, RTL-SDR Blog ADS-B LNA) and active antennas through the coax cable
  • Can be enabled in software (see V3 users guide).
• Aluminium case and passive cooling
  • These units come stock with an aluminum case and passive cooling via a silicon thermal pad
  • This stops reception failing due to heat when used above ~1.2 GHz
• Improved Antennas
  • We provide an excellent dipole antenna starter kit for newbies
  • Use the included mounts and extension cable to mount the dipole in good position for optimal reception
  • Receives terrestrial and VHF satellite signals
• Various additional improvements compared to other RTL-SDRs
  • R820T2 tuner, higher quality passive components, a choke on the USB line to reduce USB noise, a much improved PCB design for significantly less internal spurs and noise, various break-out pads, improved ESD protection, additional bypass capacitors and ferrite power line chokes, improved front end matching circuit, a modified power design for improved long term reliability, and a better LDO.

RTL-SDR V3 - HF Direct Sampling Mode

• RTL-SDR V3 can listen to 500 kHz-28.8 MHz with direct sampling
  • Direct Sampling HF Mode
• Simply connect an HF antenna to the SMA port, and choose the Q-branch mode
• There is a built in 25 MHz low pass filter, but additional HF filters may be required for optimal performance (e.g. to attenuate strong MW AM)

• Short video showing this

Wiring

• SPDT switch
  • One switch pole powers the card (turns off 12V)
  • Other switch pole switched in/out the Upverter
  • Could just move the cable

Enclosure

• Board fits perfectly in
  • Extruded Aluminum Enclosure Box - 94mm x 83mm x 30mm
  • Card just perfectly matches

Alternate Designs

• Cheaper/Better options
• Ham It Up
  • $39.95
• Ham It Up Plus
  • $49.95