Category: HF

Using an Airspy HF+ with SDR# and WSJT-X to Decode FT8 + SpyServer FT8 Decoding Demo

Over on YouTube user TheGazLab has uploaded a video that reviews the Airspy HF+, and also shows how to use the HF+ with SDR# and WSJT-X in order to create a FT8 monitor. The Airspy HF+ is high dynamic range HF/VHF receiver designed for DXing.

In the video TheGazLab demonstrates to us the decoding in real time, and explains the CAT control SDR# plugin that he's using. The CAT control plugin when combined with a virtual serial port driver allows the WSJT-X program to automatically tune SDR# to the FT8 frequency selected in WSJT-X.

Later in the video he also discusses the SpyServer network which allows SDR# users to connect to remote public Airspy and RTL-SDR units over the internet. He demonstrates connecting to a public server in the UK, and decoding FT8 via the remote server. The video also shows the new SpyServer interface by  which nicely lays out the world SpyServer network on a map, making it easy to choose a desired location to listen to.

Airspy HFPlus, SDR# and WSJT-X with full CAT control decoding FT-8

Creating a Standalone WSPR Receiver with an RTL-SDR V3 and Raspberry Pi 3

Thank you to Zoltan for submitting his scripts for installing the rtlsdr-wsprd WSPR decoder onto a Raspberry Pi, and showing us how to configure it for an RTL-SDR V3 dongle running in direct sampling mode. This set up allows users to create an extremely low cost and permanent RX WSPR monitor.

WSPR is an amateur radio digital HF mode designed to be decodable even if the signal is transmitted with very low power and is very weak. It can be used to help determine HF radio propagation conditions as WSPR reception reports are typically automatically uploaded to wsprnet. Direct sampling mode on the RTL-SDR V3 allows you to receive HF signals without the need for an upconverter. For best results it is recommended to use a simple bandpass filter for the band of interest.

Zoltan's tutorial comes with a companion YouTube video where he demonstrates his set up. He uses a random wire antenna on his roof directly connected to an RTL-SDR V3, which is connected to a Raspberry Pi 3.  The Pi 3 communicates to his home network via an Ethernet cable.

Making a standalone WSPR receiver with RPi and RTL-SDR V3 using rtlsdr-wsprd

A Tutorial on Receiving HF SSTV with a Raspberry Pi and RTL-SDR V3

Thank you to Giuseppe (IT9YBG) who has written in to share his tutorial about setting up a direct sampling RTL-SDR V3 based SSTV receiver on a Raspberry Pi. He writes that he uses the receiver to continuously receive images at 14.230 MHz, but with a frequency tweak in the command line code the system could also be used to receive the VHF SSTV images sent by the ISS.

In the tutorial he uses the free QSSTV software for decoding. An RTL-SDR together with the CSDR DSP software is used to set up a command line based receiver, which pipes the SSTV audio into a virtual audio sink, and then into QSSTV. The receiver setup procedure is similar to the method used in our RTL-SDR V3 QRP monitoring station tutorial, and is a very nice way of setting up an efficient command line based RTL-SDR audio output.

QSSTV Running on a Raspberry Pi with RTL-SDR V3 Radio
QSSTV Running on a Raspberry Pi with RTL-SDR V3 Radio

RadioForEveryone: RTL-SDR Max USB Cable Length, Dongles Image Gallery, Ham-it-up Plus Review

Recently Akos has uploaded three new posts on his RadioForEveryone blog. The first post is a review of the "Ham-It-Up Plus", which is a US$65 upconverter that allows you to listen to HF on RTL-SDR dongles without direct sampling. Compared to the non-plus Ham-It-Up, the plus version includes a TCXO and the noise source circuit is populated. In his post Akos reviews the history of the Ham It Up generations and discusses the connectors and power options. He also reviews the performance and finds that the Plus seems to have better SNR.

In the second post Akos has uploaded his collection of various images of different RTL-SDR dongle brands. The images include circuit board photos so you can easily compare the differences in design between brands.

Finally the third post is an experiment to determine the maximum USB cable length that can be used with RTL-SDRs. His results show that the maximum is 9 meters which is actually more than the USB2.0 spec which states 5m as the maximum. We note that longer than 9m cable runs can also be achieved by using active repeater USB cables or USB hubs.

Testing RTL-SDR max coax length
Testing RTL-SDR max coax length

Connecting an RTL-SDR Panadapter to a uBITX Transceiver

The uBITX is a US$129 HF SSB/CW QRP transceiver kit that works from 3 MHz to 30 MHz with up to 10W TX power. It's a fully analogue radio, but it can be combined with an RTL-SDR to create a panadapter display thanks to a tutorial released by KD8CEC.

The method requires that you use the custom CEC firmware, or modify other firmware,  as this appears to change the output frequency at the tap point. The tap point is made accessible by soldering on an extra SMA connector for the RTL-SDR to connect to. The rest of the work is entirely performed in the uBITX software manager, Omni-Rig and SDR-Console V3.

uBITX with RTL-SDR Panadapter
uBITX with RTL-SDR Panadapter

An Introduction to SDR and SDR Applications for Shortwave Listeners

Over on the SWLing Post blog, author Thomas Witherspoon K4SWL has uploaded a new article titled "Software Defined Radio Primer Part 1: Introduction to SDRs and SDR applications". The article originally appeared in the June 2018 issue of The Spectrum Monitor magazine, which can be purchased online for $3 per issue.

The idea behind the article is to introduce people to SDR from a shortwave listening point of view, so high performance HF SDRs like the Airspy HF+, Elad FDM-S2 and WinRadio Excalibur are discussed. Thomas notes that these SDRs can perform as well as traditional DX-grade receivers that can cost two to three times more. He also explains what advantages SDR's bring to the shortwave radio listening hobby. This may be a good article to show those still using older hardware radios that haven't yet converted to the SDR world. 

The article is currently part one of a three part series, with parts two and three to be released in October and November.

DXing with SDR in a Car
DXing with SDR in a Car (Photo: Guy Atkins)

Japanese RTL-SDR Products Now Available for International Shipping on

Thanks to 'Nobu' for letting us know that his RTL-SDR products sold on are now available for international shipping (in Japanese, please use the Google Translated version if needed). Before offered international shipping you had to use a third party Japanese forwarding service in order to purchase his products.

Japan has a strong RTL-SDR scene, with a few small Japanese companies and individuals (including Nobu) selling custom RTL-SDR products on their local Amazon store. Products such as upconverters, galvanic isolators, LNAs, filters, cooling products and more are available. Back in 2015 we reviewed some of these products in a post available here. Since then we've found continued use in particular with the galvanic isolator which helps reduce noise from the computer and nearby electronics at HF frequencies. 

Some Japanese RTL-SDR Products available for International Shipping on
Some Custom Japanese RTL-SDR/RF Products available for International Shipping on

Soft66IP: An OpenWebRX RTL-SDR Internet Server now Crowd Funding on Kickstarter

Over on Kickstarter a retrofit PCB for RTL-SDRs called Soft66IP has appeared for crowd funding. The PCB includes a 50 MHz upconverter and RF amplifier on board and incorporates space to plug in an Orange Pi Zero single board computer, and an RTL-SDR.

The project is by Kazunori Miura who is the creator of the Soft66 range of RTL-SDR retrofit products. The kickstarter appears to be for the "Soft66IP", which has been around since early 2017. The main difference appears to be that now OpenWebRX is preloaded on the SDCard, and that there is a custom script running on the Orange Pi Zero which allows you to choose between OpenWebRX and HDSDR. Presumably clicking on HDSDR runs an rtl_tcp server, which can then be connected over the network.

The idea is that this system will be used together with software like OpenWebRX, which would enable the RTL-SDR and radio stream to be accessed online from anywhere in the world via an Ethernet connection. Examples of OpenWebRX receivers can be found on, just search for "RTL-SDR" on the page to find relevant examples.

There are several support options, with the main board (without Orange Pi Zero or RTL-SDR) starting at US$22, and US$88 for the main board including RTL-SDR, Orange Pi Zero, enclosure and SD card. The system could probably be home built for much cheaper, but there is a convenience in purchasing a ready to use system. Although if you're interested in HF and want an internet connected SDR, then you might be better off shelling out for a $299 KiwiSDR instead, which is also an OpenWebRX based SDR.

Soft66IP: Main board + RTL-SDR + Orange Pi Zero.
Soft66IP: Main board + RTL-SDR + Orange Pi Zero.