Difference between revisions of "WA3TFS SDR Upverter Design"

Revision as of 17:14, 14 October 2021

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

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)