Tagged: rtl-sdr

QuestaSDR (Formerly UnoSDR) Updated: Now Supports Airspy and many new Features

Back in March Vi Vitaliy wrote in to let us know about an RTL-SDR compatible SDR program called UnoSDR that he had been working on. Vi now writes that the software has been updated, and the name has been changed to QuestaSDR to avoid confusion with SDRUno – SDRplays official software package. Vi writes:

In new version I added support AirSpy r2, AirSpy mini, Perfomance Window, Record AF, record and play iq raw data, frequency bookmarks, waterfall color scheme, change fft size, fps … calibrate options, support if converter.

The software is still in beta, and Vi would be interested in hearing any feedback or bug reports if you have any.

QuestaSDR can be downloaded from sdr-labs.com.

QuestaSDR (Formerly known as UnoSDR)
QuestaSDR (Formerly known as UnoSDR)

Receiving Outernet with a Grid Antenna and LeanDVB

Recently Luigi Freitas wrote in to us and wanted to share his fairly unique Outernet setup which is based on a Grid dish antenna, low cost SPF-5189 LNA, C.H.I.P mini single board computer generic RTL-SDR, and the open source LeanDVB decoder software.

Last month we made a post about LeanDVB, a lightweight DVB-S decoder, which with a few configuration changes can be used to also demodulate the Outernet signal. Luigi places his 2.4 GHz WiFi grid antenna (which still works for the 1.5 GHz Outernet signal) on a tripod and points it towards the Outernet satellite in his area. He connects the antenna up to a SPF-5189 based LNA, which is a 50 – 4000 MHz LNA that is very cheaply found on eBay for about $7 USD. Then a cheap generic no-TCXO $8 RTL-SDR is used together with the LeanDVB software.

In his post Luigi shows how to set up the LeanDVB software for decoding the Outernet signal by piping the output of rtl_sdr into it, and getting all the settings correct. To get the final files he then shows how to pipe the decoded packets in the Skylark decoder, and then the files can be accessed from the regular Outernet web GUI.

The LeanDVB Decoder GUI showing a successful lock
The LeanDVB Decoder GUI showing a successful lock

Showing what Solar Power Inverter Interference Looks Like

Over on YouTube user ALI6359 has uploaded a video showing what severe interference from a neighbors poor quality solar power inverter looks like on his RTL-SDR dongle. An inverter converts the DC power produced by solar panels into AC power which is used by common household equipment. Inverters typically use switching techniques to convert the power, and this can cause RF noise if the inverter is poorly designed and not shielded.

In the video ALI6359 shows strong interference all across the VHF spectrum. He also writes in the video description that the interference also occurs all over the entire HF band. He writes:

This is what happens if you or your neighbours install a dodgy quality solar power system. i am using a uhf phased array antenna facing away from the source of interferance but i am picking up very strong interferance. just touching the antenna connector of the rtlsdr is enough for the interferance to show up. i once had a HF upconverter (stopped working now) it used to show very strong interferance through the enitre HF band. the solar inverter certainly fails the part 15 FCC requirements.

In a previous post we also showed how interference from Ethernet over powerline adapters can destroy the entire HF band as well.

A Homebrew One Transistor Upconverter for the RTL-SDR

Recently Qrp Gaijin wrote in to us and wanted to share his experiences on building a one transistor diode-ring mixer upconverter for his RTL-SDR. An upconverter for the RTL-SDR translates low HF frequencies ‘up’ into ones that are receivable by the RTL-SDR. This is a different method to the direct sampling mode used in the V3 dongles to achieve HF reception.

Qrp Gaijin’s post goes into some detail about his circuit and shows the schematic as well. He also shows the results with an active loop antenna, RTL-SDR and the upconverter in some videos. In the email to us he also notes that his upconverter is still a work in progress as the LO is quite noisy and he suspects that it may be too weak to drive the 1N4148 based diode ring mixer. There is also no filtering on the circuit yet, so there is some broadcast FM breakthrough.

Another project he worked on was attempting the direct sampling mod on a standard RTL-SDR. However, Qrp Gaijin’s method is slightly different to most attempts as instead of soldering the wires into the Q-branch holes he simply uses hot glue to hold them mechanically in place. This may be an idea to consider for those who want to attempt the mod on a standard RTL-SDR, but don’t have any soldering tools or experience.

Homebrew RTL-SDR upconverter: physical construction

Receiving SSTV Images from the ISS with a V-Dipole and RTL-SDR

During July 20 – 24, 2017 the ISS (International Space Station) was transmitting SSTV (Slow Scan Television) images down to earth in celebration of the ARISS (Amateur Radio on the ISS) 20th Anniversary. The ISS transmits SSTV images on celebratory occasions several times a year. More information about upcoming ARISS events can be found on their website ariss.org.

Over on YouTube and his blog, user Tysonpower has created a video and writeup of his experiences with receiving the ISS SSTV images using an RTL-SDR, FM Trap filter and a V-Dipole antenna. The V-Dipole antenna is a super simple satellite antenna for NOAA/Meteor/ISS etc satellites that recently became popular due to Adam 9A4QV’s writeup on it.

Despite Laptop and PC troubles, he was able to capture several images. He also notes that he was able to use a Baofeng and Yagi antenna to receive the signal indoors.

Note that Tysonpower’s YouTube video is narrated in German, but there are English subtitles available if you turn on YouTube’s closed captions which should be on by default on this video.

[EN subs] ISS SSTV Event Juli 2017 - Empfang von drinnen und V-Dipole

Configuring OpenWRT and RTL_TCP for WiFi Streaming

In his last video YouTube user GusGorman402 showed us how to install OpenWRT and the RTL-SDR drivers on a cheap used $20 router. The idea is that the router with custom third party Linux firmware can be used as a remote device for streaming raw data from an RTL-SDR over a network connection. Normally something like a $35 Raspberry Pi is used for something like this, but an old router could be cheaper and should have even better network performance as it is designed for high data rates (assuming the CPU on your router is powerful enough to run the RTL-SDR).

In his new video Gus shows how to properly configure OpenWRT and RTL_TCP for WiFi streaming of radio data. This includes things like setting up port forwarding and determining network performance.

We’ve also seen this post by GoJimmyPi which was inspired by Gus’s original video. This is a text and screenshot based tutorial which goes through the same process.

Configuring OpenWrt and RTL_TCP for wifi

SDRTrunk Setup and Use Tutorial

Over on his blog John Hagensieker has uploaded a tutorial that shows how to set up SDRTrunk with RTL-SDR dongles. SDRTrunk is an application that allows you to follow trunked radio conversations, and decode some digital voice protocols such as P25 Phase 1. It is similar to Unitrunker and DSDPlus combined into one program. It is also Java based so it is cross platform and so can be used on Linux and MacOS systems as well.

John’s tutorial contains many useful screenshots, so it should be great for a beginner. He starts from the beginning, with finding trunking frequencies over on radioreference.com, then goes on to the installation and use on Linux. He also later explains how the Airspy can be used instead of multiple RTL-SDR to cover 10 MHz of bandwidth so that multiple systems can be monitored.

SDRTrunk Running and decoding a P25 Phase 1 System
SDRTrunk Running and decoding a P25 Phase 1 System

Potentially Receiving up to 10 GHz with an RTL-SDR and Multiple SUP-24000 Downconverters

Back in 2016 KD0CQ discovered that a $5 DirectTV device with model name SUP-2400 could be used as a downconverter with an RTL-SDR for receiving frequencies of up to 4.5 GHz. A downconverter is a device that converts high frequencies such as 4.5 GHz down into a frequency actually receivable by the RTL-SDR. The SUP-2400 is able to be modified into a useful downconverter by opening it up and manually removing some mixing harmonic filters.

In his latest post KD0CQ shows how you could combine four modified SUP-2400 downconverters to create a quarduple conversion mixer which allows you to receive up to 10 GHz. The post goes into the mixing math and practicalities of this idea. KD0CQ writes that some amplification will most likely be required to push the signal through, and in the past he’s managed to receive up to 7.5 GHz.

The SUP-2400 Directv upconverter that can be converted into a downconverter.
The SUP-2400 DirecTV device that can be converted into a downconverter.