HF Shortwave Monitoring and Decoding

~150 minIntermediate

Explore the HF shortwave bands from 3–30 MHz: receive time signals, decode RTTY and FT8, monitor international broadcasters, and build a long wire receiving antenna.

Prerequisites
Everything needed before starting

Hardware

  • •RTL-SDR Blog V4 (direct sampling) or any SDR + upconverter
  • •SDRplay RSP1C/RSP2 (recommended alternative)
  • •Ham-It-Up or SpyVerter upconverter (if using RTL-SDR V3 or older)
  • •20–40 meter long wire antenna + 9:1 UNUN
  • •Copper ground rod or connection to electrical ground

Software

  • •SDR# or GQRX for HF reception
  • •fldigi for RTTY/PSK31/CW decoding
  • •WSJT-X for FT8/WSPR monitoring
  • •VB-Audio Cable (Windows) or PulseAudio loopback (Linux) for audio routing
  • •Computer with accurate time sync (NTP or GPS)
Step 1 of 813% complete
Step 120 min
HF Reception Setup with an Upconverter

HF (High Frequency, 3–30 MHz) is where shortwave broadcasts, amateur radio, maritime, aeronautical, and diplomatic communications occur. RTL-SDRs can't natively tune below ~22 MHz with acceptable performance, so an upconverter shifts the HF band up by 125 MHz (to 128–155 MHz), placing it comfortably in the RTL-SDR's sensitive range.

Upconverter options

Ham-It-Up v1.3 (Nooelec)

~$45

Most popular. 100 kHz–300 MHz input. LO at 125 MHz. Noise figure ~7 dB. Requires separate 5V power.

SpyVerter R2 (RTL-SDR Blog)

~$35

Compact, powered via bias-tee from RTL-SDR V3/V4. Good NF. Plug directly onto the SMA connector.

SDRplay RSP1C / RSP2

~$99–169

Native HF SDR, no upconverter needed. Better performance than RTL-SDR+upconverter. Highly recommended if budget allows.

SDR# / GQRX configuration

With Ham-It-Up (125 MHz LO), tune SDR# to: desired_HF_freq + 125,000,000

Want to hear 7.200 MHz?

Tune to: 7.200 + 125 = 132.200 MHz

Want WWV at 10.000 MHz?

Tune to: 10.000 + 125 = 135.000 MHz

In SDR# with SpyVerter: enable "Converter Offset" in settings and enter 125000000 Hz. SDR# will display the real HF frequency automatically.

RTL-SDR V4 direct sampling mode

The RTL-SDR Blog V4 added a hardware HF input path using the RTL2832U's direct sampling Q-branch. Enable in SDR# with Source → Direct Sampling → Q Branch. Covers 500 kHz–14 MHz with reduced sensitivity compared to an upconverter. Adequate for strong shortwave broadcasters and WWV; marginal for weak amateur and utility signals.

The RTL-SDR Blog V4 has a built-in HF direct-sampling mode (no upconverter needed) that works adequately for strong signals. For serious HF monitoring, an upconverter to 125 MHz shifts HF into the RTL-SDR's sweet spot for much better sensitivity.

HF Reception Setup with an Upconverter