Fixing USB Reset Problems for 24/7 rtl_433 Monitoring

Rtl_433 is an RTL-SDR compatible command line based tool for monitoring various 433 MHz ISM band devices, such as temperature sensors, weather monitors, TPMS, energy meters etc. A full list of support devices can be found on the rtl_433 Github.

Over on his blog “raspberrypiandstuff” mentions that he’s been using rtl_433 and an RTL-SDR on a remote headless Raspberry Pi to receive and monitor temperature and humidity from his weather station. From the data he’s able to produce some nice graphs that show changes over time.

However, one problem that he ran into was that the USB controller on the Raspberry Pi would sometimes hang. The only solution he’d previously found to fixing it was to physically disconnect and then reconnect the RTL-SDR. But now “raspberrypiandstuff” writes that he’s found a new solution which is to use a small C-program called usbreset.c. Combined with a bash script that detects which device the RTL-SDR is on the bus, this tool helps to automatically reset the USB on the Pi if it fails to keep the RTL-SDR logging 24/7 without physical intervention.

This may be a solution to look into if you’re experiencing similar issues with 24/7 monitoring on the Raspberry Pi. If you’re also interesting in rtl_433 monitoring, “raspberrypiandstuff” also has a post on creating a simple GUI for rtl_433.

Some LimeSDR Demonstration Videos

Recently Michael DG0OPK wrote in and wanted to share some videos of the LimeSDR in action that he’s uploaded to YouTube. The first video shows LimeSDR running with the SDRangel software and receiving the 950 MHz mobile phone band. SDRangel appears to be GPU accelerated so the waterfall can show a lot of detail very quickly.

The second video shows the LimeSDR transmitting DVB-S/S2 on and ODROID XU4, and the signal being received on a PC using and Airspy, and being watched live with a standard DVB-S2 TV Card. The Odroid XU4 is a single board computer like the Raspberry Pi but much more powerful.

On his channel Michael also has some other LimeSDR videos that you can check out such as testing the LimeSDR with GNURadio on the 23cm band for full duplex DVB-S2, and running the LimeSDR at full speed 60fps, 50 MHz on a i7 PC.

The LimeSDR is a full duplex RX/TX capable SDR with a 100 kHz – 3.8 GHz frequency range, 12-bit ADC and up to 80 MHz of bandwidth. A unit currently a unit currently costs $289 USD on Crowd Supply.

Interest Check: KD0CQ Pre-Modified SUP-2400 Downconverters

Over on his blog KD0CQ has posted an interest check. He’d like to know if anyone would be interested in purchasing pre-modified SUP-2400 downconverters from him. We’ve posted about the SUP-2400 a few times in the past. Basically the SUP-2400 is a cheap (about $5 – $10 USD) DirecTV device which can be modified and turned into a downconverter for your RTL-SDR. A downconverter allows you to listen to higher frequencies, up to 4.5 GHz in the case of the SUP-2400 and an RTL-SDR. 

The modification involves some decent soldering skills as it involves removing some small SMD components and using wires to bridge some points. KD0CQ writes that he’s thinking of selling premodified SUP-2400 units for $20 – $25 to interested customers. If you think that you’d be interested in this please comment on his post.

SUP-2400 Circuit.
SUP-2400 Circuit.

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

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.

Listening to July’s Arecibo Observatory Ionospheric Heating Campaign

During July 24-31 the large Arecibo Radio Observatory in Puerto Rico (the big dish antenna that you may be familiar with from the movie ‘Contact’) ran an Ionospheric heating experiment which involves transmitting 600kW of net power up into the Ionosphere. This type of experiment is used for researching plasma turbulence in the ionosphere and upper atmosphere.

“The new Arecibo ionosphere HF heater nominally transmits 600 kW net power and has a unique Cassegrain dual-array antenna design that increases gain of three crossed dipoles for each band, using the signature 1000-foot spherical dish reflector,” explained Chris Fallen, KL3WX, a researcher at the University of Alaska-Fairbanks HAARP facility. He has reported that Arecibo would use 5.125 or 8.175 MHz, depending upon ionospheric conditions, but emphasized that these are estimates and frequencies may be adjusted slightly. On July 25, Arecibo was transmitting on 5.095 MHz.

Over on YouTube Mike L. used his SDRplay RSP1 together with our BCAM HPF to record some transmissions from the observatory.

Z33T’s Review of the ColibriNANO: $350 USD 10 kHz – 55 MHz SDR Dongle

Over on YouTube Mile Kokotov (Z33T) has uploaded his review of the ColibriNANO, which is a $350 USD 10 kHz – 55 MHz direct sampling SDR dongle built by Russian company Expert Electronics. It features a 14-bit direct sampling ADC which is then decimated into 16-bits at bandwidths of up to 3 MHz, or 24-bits at up to 768 kHz. This should give it excellent dynamic range preventing any sort of overloading.

In the video Mile gives the Colibri an excellent rating. In the video description he writes:

The Colibri-NANO USB stick is a powerful direct sampling SDR receiver with frequency range from 10 kHz to 55 MHz. ColibriNANO is not another cheap USB dongle found on e-bay. This high quality SDR receiver has been developed by Expert Electronics and has strongly and solidly build aluminum body, Electrostatic discharge (ESD) protection, USB 2.0 interface and a quality SMA antenna connector.

ColibriNANO has 14 bit Ananalog-To-Digital Converter, with a clock frequency of 122.88 MHz. Coverage is 10 kHz to 55 MHz, with low pass RF-filter on 55 MHz to protect from strong FM transmitters. The filter can be turned off so you can use the receiver in undersampling mode up to 500 MHz. In that case external filters and preamlifier (like the 2m filtered preamplifier from the same producer) is recommended for maximum results.. 

This excellent little SDR-receiver has nine IQ sample rates, from 48 kHz to 3 MHz so the frequency span on the spectrum window can be changed from 48 kHz up to 3 MHz.

There are no bandpass filters in the device, So one can think that a 14-bit Analog-To-Digital Converter may be subject to overload if you have powerful transmitters nearby. But the software has extensive RF gain control, so you should not have to worry too much. 
As I said before the Analog-to-Digital Converter in this wonderful SDR-receiver uses 14 Bit, and with decimation process results in an excellent 110 dB Blocking Dynamic Range. 

Another nice feature of the ColibriNANO SDR is the combined attenuator/pre-amplifier stage, which can be fine-adjusted in 0.5 dB steps from -31 to +6 dB. Together with the low noise floor and an excellent sensitivity, the result is a receiver with excellent large signal handling capabilities. The ColibriNANO is a perfect HF little SDR scanner which can be compare with much more expensive 
The Colibri-NANO can be operated directly attached to the computer of the user, or can be used remotely at a distant location. This is done with the freely available ExpertRemote software. 

At the location of the SDR a small computer is required (for example a Raspberry-Pi) and for the internet connection can be used a relatively slow internet link. This, for example, allows you to use the SDR receiver at some quiet location anywhere on the world.
Expert Electronics Software for the ColibriNANO allows you to use all the potential of the receiver: remote operation, synchronization with the transceiver, IQ channel bandwidth up to 3 MHz, control of the preamplifier and LPF and so on…

All mode for demodulation are supported. Here are Some of the software features:
– IQ output via Virtual Audio Cable
– Compatibility with any sound card installed on your PC for the audio output
– Synchronization with transceivers via CAT interface
– Remote operation with the ColibriNANO receiver 
– Special interface to control the CW Skimmer
– Screen resolution Supports FullHD and 4K monitors

And the important thing is that All new versions of the software are free!

To control the ColibriNANO via Internet you need freely available ExpertRemote system, based on the client-server connection. This system allows you to place the receiver and server in the remote location with low RF-noise but has the internet connection. This might be some remote village or place with no electrical interference and 3G/4G Internet (or any other connection type). 

Using the ExpertRemote system you can enjoy in clear noiseless reception from your phone, tablet, notebook or PC. Even simple antennas, placed in a “quiet” place, allows you to listen weak signals from the DX-stations better than in urban area filled with all kind of RF-noise.

Another feature of this system is that the receiver’s software can be synchronized with transceivers and be used as the panorama adapter with high resolution. In that way you can use the transceiver to transmit signals, and receive on your remotely located receiver via the ExpertRemote system. 

The ColibriNANO can be used with third party software like HDSDR etc.
You can find more information about this great 14 bit SDR-receiver on Expert electronics official website.
If you are interested in Radio technic and electronics fell free to visit my web-pages:

This device appears that it will soon compete with the Airspy HF+ which is an upcoming SDR that claims similar performance for HF. We will work on comparing the two in a later review post.