APRS, LP-WAN and more with SDRangel

Its been a while since HVDN has written about the SDRangel software, its many changes and new features have been largely at fault for not having time to write about them!

Since the FreeDV demodulator post last September introduced in SDRangel v4.11.8, the software is now up to v5.14.0 as of October 11th 2020. 

Over the last year, Edouard F4EXB and a growing number of contributors have compiled 47 total new release candidates. This level of open source contribution makes SDRangel one of the most popular software defined radio software suites that supports both receive and transmit today. 

Getting SDRangel to work is now easier than ever thanks to already compiled execution packages for Microsoft Windows.  All you need to do if using Windows is look for the below in the release you want to experiment with installing. 

Linux however still offers the best overall experience, but only by a narrow margin in my opinion when comparing use between Windows x64 10 Professional compared to Ubuntu 20.04 on the same Lenovo T495 with 40GB of RAM along with a Lime SDR Mini and RTL-SDR V3 USB dongle. 

Lets talk about APRS

Either 1200 or 9600 baud communication can now be sent from SDRangel since v.4.17.0.  Receive is not yet supported which may limit its use for now. Getting this to send packets with a Lime SDR Mini was trivial once I set the channel sink to use the Lime SDR Mini.  More about the packet modulator can be read about here.

Here are a few images of SDRangel configured as well as showing it transmit, plus being received by a Kenwood TH-D74 radio. 

Setting the transmit power and antenna port in SDRangel is important based on the frequency and what you are trying to do. A few inches away between the LimeSDR mini and its small "stub antenna/dummy load" on the transmit port. 

The "high" filter and about -10dbm gave me the desired short range test I was after on an unused frequency that is part of a UHF channel plan HVDN is proposing for US use of underused spectrum in the bottom part of the US 70cm band. 

Pressing the transmit button allowed the packet to be sent and received by the Kenwood radio set to the same frequency.

It is  possible to use a USB GPS to share location data with SDRangel by adding that under the "My Position" tab in the SDRangel menu along with the proper device arguments for the GPS.

Lets talk about LP-WAN

This refers to many technologies that fall under Low Power Wide Area Networking such as LoRa and Zigbee.  In the aptly named v5.14 version of SDRangel, it is now possible to transmit various combinations of IEEE 802.15.4 based communication.  Going back a number of releases it is also possible to receive different combinations that are possible under the LoRa. 

There is far too much to say about the differences and similarities  between these different LP-WAN technologies, but the fact that SDRangel supports these two types of LP-WAN options is fascinating

Some possible applications worth exploring include controlling or monitoring utility devices and different projects that require very low power but longer range low bandwidth communication. 

Due to possible "creative" use of both the capability of these modes of communication and the transmit capability of some SDR devices like the Lime SDR mini, HVDN is not going to provide details on using these functions since they may lean towards possible malicious use by some people.

We do encourage you to have a look at our HASviolet project which allows for both the transmission and reception of LoRa based communications, along with our latest builds involving the ESP32 based TTGO T-Beam devices. 

A very good article can be found here to better explain the differences of LoRa and 802.15.4 thanks to IEEE and the authors from the Athena Research Institute in Greece