SingalsEverywhere: Running OpenWebRX on a PlutoSDR with PlutoWEB Firmware

Over on YouTube Corrosive from the SignalsEverywhere channel has uploaded a new video that shows how to install the the PlutoWEB Firmware on a PlutoSDR, which allows OpenWebRX to run directly on the PlutoSDR itself. OpenWebRX is a SDR streaming platform that enables people to connect to the SDR remotely over the internet. Multiple users can access the SDR at the same time as well. Many public OpenWebRX servers running on KiwiSDRs can be found at sdr.hu as the KiwiSDR uses it by default.

The PlutoSDR is a low cost (typically priced anywhere between $99 - $149 depending on sales) RX/TX capable SDR with up to 56 MHz of bandwidth and 70 MHz to 6 GHz frequency range. It also has an onboard FPGA and ARM Cortex-A9 CPU which can be used to run programs on the PlutoSDR itself.

Corrosive's video shows us how to install PlutoWEB which is an unofficial firmware package for the PlutoSDR. It comes preinstalled with many programs such as OpenWebRX and dump1090. He then shows how to set up OpenWebRX and then shows a demo of it in action.

OpenWebRX via PlutoSDR using PlutoWEB Firmware

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Weather Satellite Images from Geostationary COMS-1 Received

COMS-1 Geostationary Satellite Footprint
COMS-1 Geostationary Satellite Footprint https://www.wmo-sat.info/oscar/Satellites/view/33

COMS-1 is a geostationary weather satellited operated by the Korean Meteorological Agency (KMA) which was launched back in 2010. It is similar to NOAA GOES satellites as it is also geostationary orbit (@128.2°E - footprint covers all of Asia + AUS/NZ), and so is far away enough to image the entire disk of the Earth at once. Unfortunately, unlike the GOES satellites which have in the past few years become relatively easy for hobbyists to decode, the COMS-1 LRIT and HRIT downlink data is encrypted by KMA. KMA only appear to provide decryption keys to governments, research institutes and large organizations upon request.

However, recently Australian @sam210723 was able to successfully create code to decrypt the key message file and obtain the images. From a previous Twitter post of his, it appears that the encryption keys from the KMA example code are actually valid and can be used without needing to apply for a key.

Sam notes that he'll soon release a full blog post on his results, but for now he has an older post from last year that explains a bit about the satellite and decryption of the LRIT Key. His code is available on GitHub, and in a recent Twitter post he shows some example images that he's been able to receive using an Airspy SDR.

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Using an RTL-SDR and OpenCV To Create an EMI Heatmap of Circuit Boards

Over on YouTube and his blog user Charles Grassin has uploaded a short video and blog post showing how he's using an RTL-SDR EMI (electromagnetic interference) probe and OpenCV to create a visual EMI heatmap.

Earlier this month we posted about Dmitris' experiments in which he was able to create a home made EMI/EMC probe out of a loop of semi-rigid coax and an RTL-SDR V3. This type of probe is useful for determining what components or areas on a circuit board are emitting electromagnetic interference. EMI testing for PCBs may be critical for passing compliance tests.

Charles' project takes the RTL-SDR EMI probe idea a step further by combining it with OpenCV. OpenCV is an open source library of code for computer vision applications. With the EMI data generated by the RTL-SDR EMI probe, and a camera pointed at a PCB, Charles is able to overlay a heatmap on top of the visual image which reveals the EMI hot spots on a PCB.

The video below shows the EMI heatmap of an Arduino PCB being mapped out. His blog post shows some other examples like a keyboard and a hairpin RF filter. The code he's created is open source and available on his EMI_Mapper GitHub page.

EMI mapping (OpenCV and RTL-SDR)

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KerberosSDR Batch One End of Stock, Batch Two Preorders Available

If you weren't aware, KerberosSDR is our recently released 4x Coherent RTL-SDR which can be used for tasks such as direction finding and passive radar. KerberosSDR was successfully crowdfunded over on Indiegogo, and we have recently completed shipments to all backers. Currently there is only about 20 units of the batch one production left in stock.

We are currently offering discounted preorders for batch two units on Indiegogo which we expect will be ready to ship in July or hopefully earlier. If you are interested, please order soon to avoid missing out as the price will be raised again once we are shipping. Batch two will be the same as batch one except for some minor changes. For example we have decided to convert the microUSB port into a USB-C port as we have found that there are many very poor quality microUSB cables on the market which could cause issues for users. USB-C cables are generally of a higher quality.

More information about KerberosSDR is available on the Indiegogo page.

KerberosSDR Updates

Since our last post on this blog about KerberosSDR we have made some enhancements to the software.

  • The KerberosSDR code is now fast enough to run at 1-2 Hz update rates for direction finding and passive radar on a Raspberry Pi 3 B+.
  • There is now a web interface, so the KerberosSDR can be controlled via a WiFi hotspot and internet browser. Useful for use on the Pi 3 and Tinkerboard.

For future updates we are currently working on several new features:

  • Filters to remove low confidence DoA results on the Android app.
  • A secondary heatmap type display on the Android app based on signal strength, for two direction finding indications.
  • Methods to determine the center of multiple bearing intersection points.
  • Further enhancements to processing speed, possible improved results from processing gain and possible better accuracy from improved DoA algorithms.

Within the next few weeks we will also release full tutorial videos that will show how to set up and use the KerberosSDR for direction finding and passive radar with a Raspberry Pi 3 or Tinkerboard. If you prefer a text based explanation we already have a guide up at rtl-sdr.com/ksdr.

Below is an image that demonstrates the KerberosSDR direction finding Android app. A user of KerberosSDR has also submitted two of his own screenshots that show that he was able to determine the location of a GSM transmitter with a linear antenna array.

KerberosSDR Direction Finding Results
KerberosSDR Direction Finding Results. Multiple data points collected during a drive, with bearings pointing towards the TX tower (red marker). Circular array of whip antennas used at freq. 858 MHz.
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Scanner School Podcast Talks SDR Topics with Signals Everywhere Host

Recently Scanner School released episode 70 of their podcast, and on this episode they talk about various SDR topics with Corrosive from the Signals Everywhere YouTube channel. If you follow out blog, you'll know that Corrosive is a YouTuber that is consistently putting out high quality YouTube videos on a range of SDR and other radio related topics.

Scanner School is an online workshop that aims to help you get setup with an RTL-SDR based DMR/NXDN/P25 trunking system in four classes. They also have a weekly podcast. The description of this weeks podcast with Corrosive reads:

Corrosive has been working on his YouTube channel for about 4 years, and has a ton of videos on the SDR topic. If there is something that I am looking a trying when it comes to SDR, the first place I look is on Corrosive's channel.

Today we talk about some advanced SDR topics, both for receiving and transmitting.

While we talk about the more advanced topics of SDR today, I know we all have to start somewhere. If you are looking for online training to help you get started with SDR, check out our new Intro to SDR Workshop. This course will guide you though purchasing an excellent and affordable SDR to get started with.

Additionally, we will turn this SDR into a DMR, P25, and NXDN trunked receiver that can do more than your expensive scanner.


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HackSpace Magazine Discusses SatNOGS, Cubesats and More

HackSpace is a monthly magazine dedicated to modern maker projects. This month issue 18 was released and it focuses on space based projects. The HackSpace Magazine is available for free online in PDF form, and physical copies can also be purchased.  There are several interesting articles but one in particular shows us how to set up a SatNOGS ground station with a Raspberry Pi 3, RTL-SDR and a satellite antenna such as a turnstile. 

A problem with low cost satellites like cubesats is that it is difficult to monitor them as data can only be collected when they are passing over a ground station. So in areas with no ground stations data is simply lost. SatNOGS is an open source project that aims to make it easy for volunteers to build and run RF ground stations that automatically monitor satellite data, and upload that data to the internet for public access. SatNOGS ground stations typically use RTL-SDR dongles as the radio.

A related article in the magazine also discusses cubesats, giving an overview of some previous cubesat launches and what sort of payloads are available. A third article under the space topic discusses the Libre Space Foundation which is the team behind the SatNOGS and various other space based projects that aim to democratize space. Readers may also be interested in the articles showing how to build an ISS countdown timer and how to build a Slim Jim antenna.

HackSpace Magazine SatNOGS Article
HackSpace Magazine SatNOGS Article (Excerpt)
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Testing a $2 USB Powered LNA with RTL-SDR

Over on his blog '19max63' has posted about his tests with a $2 Aliexpress low noise amplifier (LNA) and his RTL-SDR. The LNA is advertised as for boosting HDTV signals, but 19max63 has found that it does a decent job on other frequencies too. It can be found on Aliexpress for less than $2 including free shipping, by searching for "TV Antenna signal amplifier". One example listing is this one.

An LNA is useful to help lower the noise figure of a radio system which results in higher SNR values (especially at the UHF and higher bands), and can be used to overcome losses in the signal chain from components like coax cables and connectors. However, an LNA will not always help and when combined with strong in or out of band signals will make reception worse by causing overload and intermodulation products. Better quality LNAs have a low noise figure, and are able to handle stronger signals and not overload so easily.

Ultra Cheap $2 LNA
Ultra Cheap $2 LNA

Upon opening the cover, 19max63 found that the cheap LNA consists of a BFG425W transistor which should cover 40 MHz to 3 GHz, but may be band limited by the passive components. The BFG425W also has a max gain of 20dB at 2GHz and a noise figure of 0.8 dB at 900 MHz. 

In 19max63's tests, the LNA was able to improve his DAB radio (174 to 240 MHz) reception significantly, allowing him to receive several extra stations. His further tests also seem to show that it does a decent job at other frequencies from 137 MHz NOAA satellites to 1090 MHz ADS-B. Many of the comparison images do seem to show signs of overloading and intermodulation, but ADS-B in particular looks to be boosted quite nicely. So this looks like it might be a very cheap way to try and improve ADS-B reception.

Check out the his post for multiple SNR comparison images.

Cheap LNA PCB
Cheap $2 LNA PCB
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SignalsEverywhere: SDR Console V3 Transmitting with PlutoSDR

Over on YouTube Corrosive from the SignalsEverywhere YouTube channel has uploaded a video showing us how to use SDR-Console V3 and a PlutoSDR to transmit ham radio voice. In the video he sets his PlutoSDR to transmit from his microphone at 445.5 MHz, and to receive at 434 MHz. He is then able to talk to a friend using a handheld who is receiving at 445.5 MHz and transmitting at 434 MHz.

SDR Console v3 Transmitting With PlutoSDR

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