Tagged: raspberry pi

Transmitting DATV with a just a Raspberry Pi

All the way back in April 2014 we first posted about how the Raspberry Pi was able to transmit FM by cleverly modulating one of it’s GPIO pins. Later in October 2015 F5OEO expanded this idea and created software that allowed the Raspberry Pi to transmit not only FM, but also AM, SSB, SSTV and FSQ. Soon after some filter shields such as the QRPi were released to try and cut down on the spurious emissions caused by transmitting using this method.

Now F5OEO has once again taken this method a step forward and has created software capable of allowing the Raspberry Pi to transmit Digital Amateur TV (DATV). The software is called Rpidatv, and can be downloaded from https://github.com/F5OEO/rpidatv. It can be run from the command line, or via a touch graphical interface if you have a touchscreen LCD screen. DATV is a DVB-S broadcast and can be decoded with an RTL-SDR by using the leandvb software which is bundled together with the Rapidatv software. Previously we’d posted about how the International Space Station intends to one day transmit DATV and that it can be decoded with an RTL-SDR.

F5OEO writes that the software is capable of generating a symbol rate from 64k symbols to 1M symbols, which is enough to transmit one video with good H264 encoded quality. He also writes that using a low symbol rate may be useful for long distance transmissions as the signal will take up a smaller bandwidth. For example a 250K symbol transmission would only need 300kHz of bandwidth. He writes that this type of transmission could easily be used in the ISM band to replace WiFi video for FPV, but that at the moment video latency is about 1 – 2 seconds and is still being improved.

Once again we remind you that if you intend to transmit using these methods where a GPIO pin is modulated, then you MUST use a bandpass filter at the frequency you are transmitting at, and that you must be licensed to transmit on those frequencies.

A DATV transmission received from a Raspberry Pi transmitter.
A DATV transmission received from a Raspberry Pi transmitter.

Setting up a Raspberry Pi Based AIS Receiver with an RTL-SDR

Over on YouTube user Tobias Härling has uploaded a video showing how he used a Raspberry Pi and RTL-SDR dongle to set up an AIS receiver. AIS stands for Automatic Identification System and is a radio system similar to ADS-B which allows you to create a radar-like system for boats. For Windows we have a tutorial on AIS reception here.

In his setup he uses rtl_ais and the kplex software and shows how to install everything from scratch. He also shows how to set the system up so that decoding automatically starts up and begins outputing NMEA data through the network when the Raspberry Pi is powered on. This way an a device like an iPad could be used to run OpenCPN to view the plotted ships.

$50 Raspberry Pi AIS-Receiver - How to

RTLSDR4Everyone: Raspberry Pi guide & choosing your first dongle

Over on his blog rtlsdr4everyone author Akos has recently uploaded three new posts. The first post is about the Raspberry Pi minicomputer and the post discusses the merits of using the Raspberry Pi with an RTL-SDR dongle. The second post provides information to help people new to RTL-SDR choose their first dongle, and weighs up options between dongles that cost $10, $20, $25, $35 and $50 dollars. Finally, the third post compares two dongles on HF performance.

Raspberry Pi3 and RTL-SDR dongles.
Raspberry Pi3 and RTL-SDR dongles.

PiTX QRP TX Shield for WSPR on 20M Now For Sale

Back in October 2015 we posted about a piece of software for the Raspberry Pi called PiTX. PiTX allows you to turn your Raspberry Pi into a fully functional RF transmitter. When combined with an RTL-SDR a full transceiver radio can be built using the QTCSDR software.

PiTX works by modulating the GPIO pins on the Pi in such a way that it is able to produce FM modulation. The major problem with using this method of producing radio is that it creates large amounts of harmonics and interference outside of the intended transmit frequency. Interference like this is illegal and could potentially disrupt life critical radio systems such as emergency services, cellphones and air traffic control.

In order to cleanly transmit with PiTX an output RF filter should be used. Recently, the team over at TAPR.org have released a 20M WSPR TX filter shield. WSPR is pronounced “Whisper” and is short for “Weak Signal Propagation Reporter Network“. It is a type of amateur radio signal that can be broadcast and received around the world by using very low transmit power. Radio amateurs use it to see how far their signal can travel when using very low power (QRP) and to investigate signal propagation conditions. 

The 20M WSPR shield sells for $20 at www.tapr.org/kits_20M-wspr-pi.html.

The WSPR shield sitting on top of a Raspberry Pi.
The WSPR shield sitting on top of a Raspberry Pi.

Raspberry Pi Docker Images for ADS-B and ACARS with the RTL-SDR

Docker is a Linux based platform which allows you to build and deploy complex applications into a self contained “container” package that contains all the needed applications and dependencies. The container is completely preconfigured to just work as soon as you install the application without the need for any extra configuration.

Over on his blog SysRun has been developing an ADS-B ready docker image for use with the RTL-SDR on a Raspberry Pi embedded computer. His post shows how he prepared and built the docker image on the Pi and how to run the docker image.

In addition he has also uploaded another post showing how to prepare, build and run an ACARS decoding based docker image on the Raspberry Pi.

In the future SysRun also hopes to upload an AIS Docker tutorial.

Raspberry Pi + Docker + RTL-SDR
Raspberry Pi + Docker + RTL-SDR

Building a Ham Transceiver with an RTL-SDR, Raspberry Pi and Rpitx

A few days ago we posted about RpiTx, a piece of software that allows you to turn your Raspberry Pi into a multi purpose transmitter by modulating the output on one of the GPIO pins.

Now over on YouTube user HA7ILM has uploaded a video showing his related software qtcsdr. Qtcsdr runs on the Raspberry Pi and interfaces with an RTL-SDR dongle and RpiTx to create a simple transceiver radio. In the video HA7ILM shows the software in action by using a microphone and RTL-SDR plugged into the Raspberry Pi, and showing the microphone transmitting via RpiTx and being received via the RTL-SDR.

Qtcsdr can be downloaded from https://github.com/ha7ilm/qtcsdr.

As always with this type of thing only transmit if you are licensed and take care with the transmitted distance and filter the antenna output when transmitting over a distance that is further than your room. Also regarding this, on the qtcsdr GitHub page the author mentions that a Raspberry Pi shield called the QRPi filter + amplifier is currently in development (white paper).

QTCSDR Control GUI
QTCSDR Control GUI
Testing qtcsdr: receiving the transmission with an RTL-SDR via attenuator

Transmitting FM, AM, SSB, SSTV and FSQ with just a Raspberry Pi

Previously we posted about the Raspberry Pi’s ability to modulate one of its pins to produce FM transmissions with PiFM. A developer (F5OEO) has recently expanded on this idea, and now the Raspberry Pi is capable of modulating and transmitting FM, AM, SSB, SSTV and FSQ signals anywhere between 130 kHz to 750 MHz.

To transmit with the Raspberry Pi all you need to do is plug in a wire antenna to Pin 12 (GPIO 18) on the GPIO port and run the PiTx software by piping in an audio file or image for SSTV. 

Important Disclaimer: While the output power is very small, you should still take great care as the carrier is a square wave, and there is no filtering on the antenna output. So any transmissions will cause harmonics all across the spectrum – possibly interfering with life critical devices. A filter *must* be used if you actually plan on transmitting with any sort of range further than your room. The predecessor PiFM has been reported to have a range of 10cm without an antenna, so it may be best to not connect an antenna to the pin if just testing. With a simple wire antenna the range is increased to 100m which could affect your neighbours. There are also strict laws and licences governing transmitting in most countries so make sure you follow them carefully. In short, get your ham licence and understand what you are doing before transmitting with any sort of amplification/range.

The code for PiTX can be downloaded at https://github.com/F5OEO/rpitx. Also see the authors (@F5OEOEvariste) Twitter account at https://twitter.com/F5OEOEvariste for some more info about PiTX.

PiTX transmitting SSTV and received in HDSDR. From PiTX's author's Twitter @F5OEOEvariste
PiTX transmitting SSTV and received in HDSDR. From PiTX’s author’s Twitter @F5OEOEvariste

Over on YouTube the author of PiTx has also uploaded a video showing a wireless doorbell being replayed with PiTx. On the video description he writes:

PiTx is a software which permit to transmit HF directly through a pin of Raspberry Pi GPIO. Unlike PiFM which transmit only in FM, PiTx is able to perform multi modulation (FM,AM,SSB,SSTV,FSQ) : it has an I/Q input to be agnostic.
The demonstration here is done in several steps :
– Record an I/Q file from a doorbell transmitter on 434MHZ (first part)
– Playing it with the Raspberry Pi using Pitx on HF on same frequency
– Listen to the doorbell receiver which recognize the signal

Conclusion : Pitx is now a real TRANSMIT SDR at very low cost. Be aware that it generate lot of harmonics and never compete with USRP or HackRF.
Goal is to popularize the transmission as rtlsdr popularize the reception.

New Raspberry PI Remote RTL-SDR GUI Software: MNM4SDR

Recently RTL-SDR.com reader Slaven Krilic wrote in to use to announce his project called MNM4SDR which stands for Monitoring Network Manager for RTL-SDR. The software allows you to set up a remote Raspberry PI embedded computer with an RTL-SDR dongle attached and access it remotely through a Windows PC GUI.

Unlike other server software such as rtl_tcp, raw IQ data is not sent over the network. Instead audio is first compressed in lossless FLAC or OGG formats. This allows you to use much slower network or internet connections. The software also allows you to collected RF scans over a large bandwidth in a similar way to rtl_power.

The software works over an SSH connection and requires that you have RTL-SDR and VLC set up on your Rasperry Pi first.

MNM4SDR: Monitoring Network Manager for RTL-SDR
MNM4SDR: Monitoring Network Manager for RTL-SDR