As part of their senior project Matthew May & Brendan Harlow of Champlain College worked on a project that involved creating their own software defined radio based portable cell phone network. If you're interested their setup is nicely documented on their project page. Basically it consists of a bladeRF software defined radio and Raspberry Pi running the YateBTS base station software. This is nothing new in terms of work done before, but the clear documentation makes it a good starting point for anyone looking at building their own SDR based cell basestation.
A custom cell basestation may be useful for those in remote areas without commercial cell phone reception, during disasters or even just to create a type of secondary network in your home.
A few months ago satellite data broadcasting company Outernet created a limited number of prototype receivers that combined an L-band satellite patch antenna, LNA and RTL-SDR into a signal unit. This was never produced in bulk as they found it to be too noisy having the RTL-SDR so close to the antenna, but nevertheless it still worked fairly well.
Over on YouTube max30max31 bought one of these prototype units and made a video about using it for receiving and decoding various L-band satellite signals. In the video he first shows an overview of the product and then shows it receiving and/or decoding some signals like Inmarsat STD-C, AERO and Inmarsat MFSK.
Over on the SWLing Post blog we’ve seen news of this new SDR based car radio called the Gospell GR-227. Gospell is a Chinese manufacturer of various broadcast consumer radio products including DRM receivers. It is intended to be an adapter for your car that lets you listen to digital broadcast stations such as DAB/DAB+ on VHF and DRM on UHF, but it can also be used for standard AM and FM reception. From the product sheet it looks like it will simply plug into you car USB port, and output audio through that port into your cars head unit. Control of the unit is through an Android app.
There doesn’t seem to be anything stopping someone from using this outside of a car though, so perhaps depending on the price and software hackability available it might make a good PC or Raspberry Pi based HF receiver for all modulation types too.
Over on the Gospell Facebook page are images showing the Gospell running at IBC 2017 and next to other upcoming SDR based digital broadcast receivers like the Titus II.
Gospell SDR Connected to a Car Radio Head Unit
No word yet on a release date or pricing. The press release reads:
Chengdu, China, September 04, 2017 – A new adaptor specifically designed for in-car use that simplifies digital radio on the road will be introduced at IBC by Gospell.
GR-227 is a small, low-cost adaptor that acts as an aftermarket add-on to car stereos receiving high-quality digital broadcast programs and data application, and serving it to the car audio system over a USB cable. Based on software defined radio technology, GR-227 is compatible with DAB, DAB+, DRM and is DRM+ ready. It is also powerful enough to support digital audio decoding such as extended HE-AAC (xHE-AAC).
GR-227 literally works with any kind of car stereos with a USB port. Our patent pending technology allows the adaptor to behave like a thumb drive when plug into a USB port and makes it compatible with most of the music players not only in car but also for home use.
To make the most of GR-227, the Gospell Smart Tune App for Android has been included to add more features. When partnered with an Android powered car stereo, the App not only allows for playback of the broadcast audio program but data application which brings much fun to car entertainment.
By connecting the supplied triple band active antenna which can be attached to the windscreen through the SMA antenna connector, the reception in DRM, FM and DAB bands can be significantly improved, offering maximum flexibility between different broadcasting standards.
Installing the plug-and-play GR-227 adaptor to your car is easy and doesn’t require changing your car stereo. It is one of the easiest ways to upgrade your car radio to digital without replacing anything.
The Gospell’s aftermarket car adaptor range starts with USB model but more will follow to support more car stereo types.
Haochun Liu, DRM director, Gospell, said: “By leveraging SDR, we can now combine multiple broadcasting standards together to offer flexibility and cost advantages, coupled with easy installation without the necessity of buying a new car stereo as in traditional solutions.”
For additional information, please visit www.goscas.com or contact Gospell sales at [email protected].
About Gospell
Founded in 1993, Gospell Digital Technology Co Ltd (GOSPELL). is a private hi-tech enterprise with R&D, manufacturing, business consultancy and planning, trade, delivery, project implementation and after sales service, acting as a complete DTV and triple-play solution provider for Digital TV/OTT related projects. Headquartered in GOSPELL INDUSTRIAL PARK at Chenzhou, Hunan Province for CPE related production manufacturing, GOSPELL also has its office in Shenzhen for business/marketing management and administration, in Chengdu for R&D and headend/transmitter system production/debugging and Customer Service Center, and in 12 cities in China as well as international offices in India, Africa and Mexico.
Thank you to Adrian for submitting his video about using the Android App called QRadioLink and an RTL-SDR to decode digital amateur radio voice transmissions. Adrian writes that in the video the RTL-SDR connects to the Android phone with a USB OTG cable and uses a sample rate of 1 MSPS. He also writes the following about QRadioLink:
QRadioLink is a building platform which allows experimenting with VHF-UHF SDR transceivers using different modulation schemes for digital data transmissions. So far digital voice and text transmission is supported, using either a narrow band modem and Codec2 or a high bandwidth modem and Opus. Supported hardware includes the RTL-SDR, Ettus USRP, HackRF, BladeRF and in general all devices supported by libgnuradio-osmosdr.
QRadioLink running on Android (Debian chroot) with RTL-SDR
Back in June Gus Gorman showed us via a YouTube tutorial and demo how to monitor ATCS (Advanced Train Control System) signals from trains. ATCS is found in the USA and is used for things like communications between trains, rail configuration data, train location data, speed enforcement, fuel monitoring, train diagnostics and general instructions and messages. Gus used an RTL-SDR and the ATCS Monitor software to decode the signals and give us a view of the current state of the railway line.
In his latest video Gus gives a better demonstration of the software by parking outside a train station so that he can receive many more signals from the trains. At the start of the video he shows the track view of BNSF trains, and then later switches over to the Union Pacific track view.
Over on his YouTube channel GusGorman402 has uploaded a video that shows how he was able to capture and decode data from a USGS (United States Geological Service) streamgage.
A streamgage is a sensor for streams and rivers that is used for measuring the amount of water flowing. In particular the ALERT (Automated Local Evaluation in Real-Time) streamgages are designed for the warning of flooding. The ALERT streamgages are wireless with some transmitting data upwards to the GOES-15 geosynchronous satellite with a cross Yagi and some transmitting locally via a standard Yagi. Gus shows if you’re close to a streamgage antenna then you can still receive the signal on the ground with an RTL-SDR. Gus also mentions that all streamgages in his area are slowly being converted to satellite uplink.
His first video simply shows the RTL-SDR receiving a Streamgage satellite uplink signal at 400 MHz. In his second video he moves to a streamgage with terrestrial link at 170 MHz and shows that the data can actually be decoded into a binary string using minimodem. Another program called udfc-node can then be used to turn the data into a human readable format. The binary packets consist of an address that identifies the particular streamgage, and some data that describes the current level of the stream and how much precipitation it has counted.
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
Over on YouTube user Keld Norman has uploaded a video showing how he uses an RTL-SDR with gr-gsm and a Python script to create a simple IMSI catcher. IMSI stands for International mobile subscriber identity and is a unique number that identifies a cell phone SIM card in GSM (2G) mobile phone systems. For security IMSI numbers are usually only transmitted when a connection to a new cell tower is made. More advanced IMSI-catchers used by governmental agencies use a fake cell tower signal to force the IMSI to always be revealed. This way they can track the location of mobile phones as well as other data like who or when you are calling.
In the video Keld uses a Python script called IMSI-Catcher. This script displays the detected IMSI numbers, country, and mobile carrier on a text display. The video description shows how to install GR-GSM and the IMSI-Catcher script on Ubuntu.
