Category: Amateur Radio

Receiving Kicksat Telemetry with the RTL-SDR

Recently a bunch of amateur radio nano-satellites known as ‘Kicksats‘ were launched on the latest SpaceX rocket. So far the Kicksat carrier has been successfully deployed, which is essentially the box containing the nano-satellites. On May 4, the nano-satellites known as ‘sprites’ are due to be deployed from the carrier.

Both the carrier and Kicksat sprites have telemetry signals which are receivable with the RTL-SDR. As the sprites transmit using only 10mW of power, a high gain Yagi antenna and an LNA are required to receive their signals.

Over on his blog, Dolske has been trying to receive and record the Kicksat carrier using his RTL-SDR. He was able to capture a telemetry packet at 437.505 MHz using SDR#. He then tried to use QTMM AFSK1200 to decode the packet, but has been unsuccessful so far probably due to the weak signal he received.

Kicksat 'nano' satellite sprite.
Kicksat ‘nano’ satellite sprite.

Softrock Ensemble II vs the RTL-SDR + Upconverter on Shortwave

Over on YouTube user mutezone has posted a video comparing the RTL-SDR with upconverter against a Softrock Ensemble II software defined radio. The Softrock Ensemble II is an SDR dedicated to the HF frequencies and is thus expected to have better performance for that purpose. Mutezone writes

A performance between the Softrock Ensemble II vs the RTL-SDR (R820T) on shortwave. Here we are trying to see which one is best at receiving AM broadcasters. Both SDRs were using the same longwire antenna connected to an ATU (Antenna Tuning Unit).

Although I know this comparison is somewhat unfair, since the RTL-SDR is not meant for shortwave & the Softrock is, it is to show that there is a difference in performance, even though the RTL-SDR has a much wider frequency range & cannot be beaten when it comes to value for money. My opinion is that if you want an SDR that should deliver on HF / Shortwave performance, then go for a dedicated one like the Softrock, Afedri, SDR-IQ or any others that do the same job on the market. Even when using a decent HF Upconverter, the RTL-SDR will still not match the performance of more upmarket HF SDRs.

Softrock Ensemble II vs RTL-SDR HF/ Shortwave test

Receiving SO-50 Saudisat 1C with the RTL-SDR

Over on YouTube user Orlando Lima shows reception of the SO-50 Saudisat 1C satellite. Saudisat is an amateur radio satellite with an FM radio repeater. Orlando listened to the downlink frequency at 436.795 MHz using an RTL-SDR, Yagi antenna and Orbitron software to track the downlink frequency in SDR#.

Receiving Weather RTTY and FAX with the RTL-SDR

YouTube user Tiago Sousa shows how he was able to receive weather Radioteletype (RTTY) data using the RTL-SDR, an upconverter and MultiPSK. Weather RTTY is broadcast by weather services such as the Deutscher Wetterdienst (DWD) which is broadcast from Hamburg, Germany. It is intended for people at sea.

Tiago used an RTL-SDR with upconverter and an 11 meter long wire antenna. For the software he used SDR# and piped the audio to MultiPSK.

Weather RTTY - DWD Hamburg heard in Portugal

Tiago has also uploaded a second video showing him receiving Weatherfax with the same setup. Weatherfax is a signal that transmits a fax image showing weather patterns.

Weather Fax - DWD Hamburg heard in Portugal

Decoding APRS with SDR#, APRSISCE32 and an RTL-SDR

Over on YouTube user k2nccvids has posted a video showing how he was able to decode APRS signals and plot them on a map using APRSISCE32. APRSISCE32 is an advanced Automatic Packet Reporting System (APRS) decoder which has mapping capabilities and can also connect to the internet as an iGate. APRS is used by amateur radio hobbyists to send data like messages, announcements and also GPS coordinates.

Building an Upconverter from the LNA4HF

Adam the manufacturer of the LNA4HF has recently uploaded a video showing how to easily build an upconverter from the LNA4HF. The LNA4HF is a low noise amplifier intended for use with SDRs like the RTL-SDR. The video shows how to connect up two components, the Mixer and Oscillator which are required to create the upconverter.

HF upconverter built from the LNA4HF

Receiving D-STAR Voice with DSD 1.7 on Windows

Recently we posted about PU2VLW’s project where he was able to decode and listen to D-STAR voice using an RTL-SDR and SDR# running on Windows connected via physical audio cable to a second Linux machine running DSD 1.7.

Now a RTL-SDR.com reader by the name of “Skywatcher” has written in to tell us how he was able to compile DSD 1.7 on a Windows PC using Cygwin. This allows him to decode D-STAR audio on a single Windows PC. Skywatcher kindly sent us the steps he used to compile DSD 1.7 on Windows.

1. Download the zip archive for dsd-1.7.0 from here: https://github.com/szechyjs/dsd and then unzip the archive, so that you get the folder dsd-master, which includes all the source files.

2. Download the zip archive for mbelib-1.2.5 from here: https://github.com/szechyjs/mbelib and then unzip the archive, so that you get the folder mbelib-master, which includes all the source files.

3. Download and install the Cygwin environment. It is important to use the 32 bit version. It will not work with the 64 bit version. In the installation process, you also have to make sure that you choose gcc (the compiler) for installation.

4. Within the Cygwin command window, use gcc, to compile every .c file within the folders mbelib-master and dsd-master (subfolders can be ignored), so that you will get an .o file (object file) for each source file.

5. Copy all the resulting .o files from mbelib-master to dsd-master and use gcc again to link all the object files, so that you will get the final executable dsd.exe. This final step also has to include the sndfile library from Cygwin being mentioned in the call of gcc, otherwise it will not work.

6. In order to start dsd.exe, it is necessary to copy cygwin1.dll to the same folder, where your built dsd.exe is. It is very important that the version number of the dll is being lower than 1.7.26, otherwise dsd.exe will crash. If this is not the case for your dll, you have to find an alternative version from the internet. Additionally, it may be necessary to copy more dlls, needed by the sndfile library, next to your dsd.exe. This may depend on your environment variables of your system.

7. For decoding D-Star, you should call DSD like following: dsd -i /dev/dsp -o /dev/dsp -fd

8. For best results, make sure that all your SDR# and VAC sample rates are set to 48kHz and that you have disabled “Filter Audio” in SDR#. Also, the audio volume of SDR# should not be set to high.

With DSD 1.7 running on Windows, Skywatcher was able to get these results shown in the video links below.

https://www.youtube.com/watch?v=5qpwnTDvI-Q

https://www.youtube.com/watch?v=30GcI4LDjdg&feature=youtu.be

EDIT: Reader Kotelnikov007 from the comments section has been kind enough to upload a pre-compiled windows version. https://mega.co.nz/#!Ft9WFbgQ!sOhsUeMC83Xi5Wxjr4eEPoc0WuM0cJOM2bq9DnE4dWE

EDIT 2 (30/12/2016): The above link seems dead. Reader Adrian wrote in to submit his compilation which is available at https://mega.nz/#!jJZRALrb!NylT4jmZIBwCyZqU05EaX8wqObxuaqeTzCD8hHP5gO8.

Adrian also writes

– The list of the required DLLs to make it work are these:
https://twitter.com/CodingFree/status/813788401610739712
– It is needed to load sndfile library (already prebuilt in Cygwin).
– It needs MBE, but also the ITPP libraries.

Using the RTL-SDR as a Panadapter

PW2VLW’s shows on his blog how to adapt an Icom IC-706 hardware radio to be able to use an RTL-SDR as a cheap panadapter (Note site is in Portuguese, so use Google Translate). A panadapter is device that allows you to visually see the RF spectrum and waterfall being received by the ham radio.

He shows instructions on how to perform the required modification to get the IF output of the ICOM, and also shows how to interface the PC with the ICOM so that it may be controlled directly via HDSDR.

Panadapter
Panadapter