Category: Applications

An RTL-SDR Panadapter for the TECSUN PL660 Shortwave Radio

Thank you to Joseph IT9YBG for submitting his article describing how he has made an RTL-SDR based panadapter for his TECSUN PL660 portable shortwave radio. The post is a series of pictures that show how Joseph was able to open the PL660 and connect a coax cable to the IF output, and mount the connector on the plastic cover for easy access. He then connects that IF output to the RTL-SDR via a 10pF capacitor.

The result is that Joseph is able to receive the IF output of the PL660 at 451 kHz in SDRUno with his RTL-SDR Blog V3 running in Q-Branch direct sampling mode. He notes that although the IF bandwidth from the PL660 is small, it is possible to decode digital signals by passing the audio demodulated by SDRUno into decoding software. 

RTL-SDR Blog V3 Panadapter for the Tecsun PL660

Receiving Analog TV from Turkmenistan Unintentionally Bouncing off a Russian Military Satellite

Over on Twitter @dereksgc has been monitoring the 'Meridian' communications satellites, which are Russian owned and used for civilian and military purposes. The satellites are simple unsecure repeaters, meaning that actually anyone with the hardware can transmit to them, and have their signal automatically rebroadcast over a wide area. This has been taken advantage of recently by anti-Russian invasion war activists who have been trolling the satellite with SSTV images of the Ukrainian flag, as well as audio.  

Apart from intentional abuse, a side effect of being an open repeater is that sometimes the satellite can pick up powerful terrestrial signals unintentionally, such as analogue broadcast TV from Turkmenistan. Over on his blog, @dereksgc has written up an excellent post documenting the background behind this finding, his entire setup involving the hardware he's using and how he's aligning with the satellite, and what software he is using to decode the TV signal. In his hardware setup he notes that he uses a HackRF, but that a RTL-SDR would suffice.

Testing Tire Pressure Monitoring System Sensors with RTL-SDR and rtl_433

Thank you to Ross for writing in and sharing with an articles that he's written about testing Tire Pressure Monitoring System (TPMS) sensors using an RTL-SDR and the rtl_433 decoder.

TPMS is a system installed on many modern cars (or retrofitted on older cars) that wirelessly monitors the tire pressure on vehicles in order to provide dashboard information that can improve safety and fuel economy. TPMS system typically transmit on license free bands, such as 315 MHz which can easily be received with an RTL-SDR.

Ross owns a 2008 Toyota Tacoma which has a built in TPMS system. Unfortunately he found that one of his sensors was broken as the TPMS warning light was consistently on, despite knowing that his tire pressure was correct.

Instead of purchasing an expensive TPMS diagnostic tool, Ross broke out his RTL-SDR and fired up rtl_433 which already contains a ready to use TPMS decoder. From the data received, Ross was able to determine that only three sensors were transmitting. Ross then goes on to use the RSSI signal power strength measurements provided by the rtl_433 output, while moving the antenna next to each wheel to determine exactly which wheel had the faulty sensor.

Ross's post goes into further details about his setup and the data he received from the sensors. He also created a follow up post, describing a bash script he wrote to automate the process.

TPMS Data Received

SignalsEverywhere: Review of SDR++ on Android

In our last post we mentioned that a 'pre-release' public version of SDR++ for Android was recently released. Now over on the SignalsEverywhere YouTube channel Sarah has uploaded a new video where she reviews and demonstrates the new SDR++ Android App. 

In the video Sarah demonstrates how to connect and start a SDR, shows SDR++ in action, then tests listening to NOAA weather audio reports, Inmarsat reception via the bias tee support, P25 and broadcast FM. She also shows how it's possible to use the split screen multitasking feature on Android to send audio from SDR++ into APRSdroid for APRS decoding.

She goes on to show how to fine tune the screen PPI resolution for different sized devices, and how to set up multi-VFO listening on the HF bands. Next, she compares the audio decoding quality between SDR++, SDRTouch and RFAnalyzer. Finally she shows that a HackRF running at a wideband 20 MHz of bandwidth can run smoothly. 

The Android SDR App That Beats Them All! Supports RTL-SDR Airspy HackRF and Many More!

SDR++ Android App Public Pre-Release Now Available

SDR++ is an open source program compatible with most software defined radios including the RTL-SDR that has been going through rapid development making it now one of the top software choices.

Yesterday a public 'pre-release' Android version of SDR++ was made available for download. The release is announced as a 'pre-release' due to various bugs still existing. However, we note that we have been testing a private release for the past few weeks, and we can say that it is working great most of the time. The Android App replicates most of the desktop experience perfectly, and it operates very smoothly on most modern devices.

The author Alexandre Rouma writes:

I'm happy to release the first public pre-release of SDR++ for android. It's still quite early and has a few bugs and quirks that you might run into:

  • SDR MUST be plugged in before starting SDR++ and you MUST press refresh in the SDR source you're using before pressing play if you first plugged in the SDR or unplugged/replugged, otherwise expect a crash. The USB handling still needs some work.
  • There are still a few UI glitches
  • There is no easy way to select a path for recording or file for playback
  • The audio sink on Android may have higher latency
  • All menus sometimes close when app goes in the background.
  • Resizing the menu and/or waterfall is kinda fiddly, be precise when trying to grab the resize bar!!!
  • At some size menu sizes, the app crashes. If this happens, start in landscape
  • On Samsung devices, the keyboard doesn't always work for some obscure reason...


  • Android 9.0
  • OpenGL 2.1

Since phones usually have a high screen resolution, set the DPI scaling in the Display menu or you'll have a hard time using the app.

Current Device/Protocol Support:

  • Airspy
  • Airspy HF+
  • HackRF
  • PlutoSDR (network only)
  • RFspace
  • SDR++ Server
  • SpyServer

In any case, I'd love to get some feedback on it, so feel free to try it out and let me know!

Download Here:

PS: If you like this work, feel free to support me on Patreon, since putting it on the App Store won't be cheap and I want to make sure it's completely free with no ads!

SDR++ Android App Screenshot. Credit: goscickiw

New York Times Story on Intercepted Russian Forces Radio Communications

The New York Times have recently run an incredible video story about how Russian radio communications are being intercepted and recorded by ham radio operators and open source radio monitoring hobbyists in Ukraine. Some of the communications reveal the extent of the logistical issues experienced by the invading forces, and perhaps have even recorded evidence for war crimes.

It appears that much of the invading Russian forces use simple unencrypted analogue voice over HF channels that can be intercepted and recorded by anyone with an HF software defined radio, or anyone willing to monitor nearby web-based SDRs like KiwiSDRs and WebSDRs. In the video screenshots of recordings played back in SDR# and various WebSDRs are displayed.

The story focuses mostly on the audio recordings that highlight communications between Russian forces discussing attack plans, including plans to bombard residential areas with artillery. These recordings are cross-referenced with reports and videos of actual tank sightings and destruction in the areas discussed on the radio.

A later recording highlights communications from a distressed Russian vehicle under attack, requests for air support being unfulfilled, and urgent requests for supplies like fuel, food and water. 

Russia Struggled to Capture a Ukrainian Town. Intercepted Radio Messages Show Why.

Some of the monitoring projects involved are highlighted in the story and they include, Project Owl, Ukrainian Radio Watchers, ShadowBreak and NSRIC (Number Stations Research and Information Center). We are also aware of at least one other organization attempting to record communications within Ukraine as well that may be making use of RTL-SDRs, HackRFs and other SDRs.

Detecting Interstellar High-Velocity Clouds with a Radio Telescope and an RTL-SDR

Over on Facebook Job Geheniau has recently described his success in detecting interstellar high-velocity clouds with his telescope consisting of a 1.8 meter dish, amplifiers, band pass filters, and an RTL-SDR.

High-velocity clouds or HVC's are areas of interstellar gas that are moving at very high velocities relative to that of the galactic rotation.

Job has been ticking off some amazing amateur radio astronomy milestone results recently with his radio telescope and RTL-SDR. So far he has managed to image the Cygnus star forming region, complete a Hydrogen line survey of the northern sky, measure the galactic rotational curve, and create a radio image of the milky way.

His latest post about detecting high velocity clouds reads:


CIII High Velocity Cloud detected with 1.8 meter JRT.

The receiver was a RTLSDR connected to some amplifiers, band pass filter and a 1.8 meter dish.

HIGH VELOCITY CLOUD CIII with JRT (Job’s Radio Telescope)

“High-velocity clouds (HVCs) are large collections of gas found throughout the galactic halo of the Milky Way. These clouds of gas can be massive in size, some on the order of millions of times the mass of the Sun and cover large portions of the sky. They have been observed in the Milky Way's halo and within other nearby galaxies.

HVCs are important to the understanding of galactic evolution because they account for a large amount of baryonic matter in the galactic halo. In addition, as these clouds fall into the disk of the galaxy, they add material that can form stars in addition to the dilute star forming material already present in the disk. This new material aids in maintaining the star formation rate (SFR) of the galaxy.

The origins of the HVCs are still in question. No one theory explains all of the HVCs in the galaxy. However, it is known that some HVCs are probably spawned by interactions between the Milky Way and satellite galaxies, such as the Large and Small Magellanic Clouds (LMC and SMC, respectively) which produce a well-known complex of HVCs called the Magellanic Stream. Because of the various possible mechanisms that could potentially produce HVCs, there are still many questions surrounding HVCs for researchers to study.”

My detection:

For JRT the High Velocity Clouds are pretty hard to detect.

The Anti Center Complex is the easiest which I detected earlier last year.

This week I tried C III. It’s at Galactic Coordinates 120 50 and has a Vlsr of -140 km/s. You can find it on the chart:

In the simulation it looks like this:

Pay attention the low Brightness Temperature (0.3 Kelvin) compared for instance with Deneb (80 Kelvin)! Pretty hard to detect with my dish.

With JRT I did a 4 hour exposure (also 4 hours of Darks in the neighborhood) at 1420.405 MHz.

The new Feed I built is very good and has a perfect ‘pitch’ at gain 25 dB.

The final result for High Velocity Cloud CIII with my 1.8 meter dish:


SignalsEverywhere: Setting up and using SDR++ Server

On this weeks SignalsEverywhere episode, Sarah demonstrates and shows us how to use the SDR++ Server, which was released as a beta earlier this year. SDR++ Server is similar to software like rtl_tcp, and Spyserver as it allows us to connect to a remote networked SDR like an RTL-SDR. Compared to rtl_tcp and Spyserver however, SDR++ Server has a huge advantage in that it is compatible with almost any SDR, and enables the full range of control options for RTL-SDRs.

In the video Sarah shows us how to activate the SDR++ server module and how to connect to a remote RTL-SDR running the SDR++ server on a Raspberry Pi. She goes on to show how to connect to other SDRs running on the Raspberry Pi as well, such as the SDRplay RSP Duo, LimeSDR, Airspy R2 and Airspy HF+ Discovery. Finally she goes on to show how to set up the server on Windows and a Raspberry Pi.

SDR++ Server | Remote RTL-SDR SDRPlay LimeSDR AirSpy and More! | Raspberry Pi and Windows Setup Tut