SDRPlay have just announced that their RSP1 unit has just been reduced in price to $99.95 USD. Their press release reads:
SDRplay are pleased to announce a price reduction for their entry-level SDR receiver, the RSP1 to $99.95 USD making it the most competitive mid-range SDR to include reception down to low frequencies without the need for an upconverter. The RSP1 provides general coverage receiver and panadapter capability from 10 kHz to 2 GHz. As well as providing SDRuno SDR software, support for popular 3rd party packages like HDSDR, SDR-Console and Cubic SDR is provided. Recent availability of an SD Card image makes for easy set up on a Raspberry Pi.
Over time we’ve seen the RSP1 reduce in price originally from $299 USD, to half price at $149 USD in March 2015 and then to $129 USD in September 2016, and now finally down to $99 USD. The newer RSP2 remains at a price of $169.95 USD.
Over on his YouTube channel Corrosive has uploaded a useful video showing how to modify a standard TV dipole to make it better for general radio use. Many TV dipoles come standard with twin lead, or very poor quality coax cable. Corrosive shows in his video how simple it is to modify and improve one of these by adding high quality coax with a BNC connector.
These TV dipoles are great as general purpose antennas, and are especially useful for making V-dipole antennas for NOAA/Meteor M2 reception.
There is a great advantage to running SDR decoder apps on a single board PC like a Raspberry Pi 3. For example instead of committing a whole PC to become a dedicated decoder, a cheap Pi 3 can be used instead. However, unfortunately many decoder apps are written for the x86 CPU architecture and/or Windows, making them impossible to run on ARM and/or primarily Linux devices like the Raspberry Pi 3.
That is unless you use an emulator combination like Eltechs Exagear and Wine. Exagear is an emulator that emulates an x86 environment on a device like a Raspberry Pi 3 which uses an ARM CPU. Wine is a Windows compatibility layer that allows you to run x86 Windows apps on an x86 Linux installation. So by combining Exagear together with Wine it is possible to run Windows apps on ARM Linux devices.
Exagear is not free (although there is a free trial). It currently costs $22.95 USD for a Pi 3 licence, and $16.95 USD for a Pi 2 licence and $11.45 for a Pi 1/Zero licence. They also have versions for Odroid, Cubieboard, BananaPi, Jetson and many other ARMv7 and ARMv8 devices like the super cheap and powerful Orange Pi’s. There are free alternatives out there like QEMU, however when we tested QEMU it was far too slow on the Pi 3 to even run notepad responsively, let alone a decoder. Exagear on the other hand seems to run apps at near native speeds, without much lag at all. So in this respect the price seems to be worth it.
We decided to test the Exagear + Wine combination on a Pi 3 and were successful in running a number of apps including Unitrunker, WinSTD-C, WXtoImg, DSDPlus, PC-HFDL, MultiPSK, Orbitron and Sondemonitor.
Trunking setup with Unitrunker on a Raspberry Pi 3
With Unitrunker we were able to set up a full trunk tracking system using two RTL-SDR dongles, rtl_fm, rtl_udp and a custom script to control rtl_udp.
Unitrunker running on a Raspberry Pi 3
In the future we may put up a full double checked tutorial with images, but for now a roughly written tutorial is presented below. The tutorial is fairly involved and assumes decent Linux experience. The tutorial starts from a fresh install of Raspbian.
The basic idea of operation is based around the fact that the RTL-SDR cannot be used directly within Wine (or so it seems). So the control signal audio is routed from rtl_fm running on one dongle into Unitrunker on Wine using alsa loopback. Then we use the old Unitrunker remote.dll method to generate a sdrsharptrunking.log file which is a text file that contains the current frequency that the voice receiver should tune to. A simple shell script continuously reads this file and extracts the frequency, and then commands an instance of rtl_udp running with the second dongle to tune to that frequency.
Over on YouTube icholakov has uploaded a video showing how effective a simple old TV bunny ears antenna can be at receiving NOAA satellite images. The old TV antenna is telescoping so it can be adjusted to be resonant for many frequencies, and for NOAA satellites about 20 inches makes it resonant. Using the antenna as a V-Dipole and placing it in a North to South direction optimizes the radiation pattern towards the sky, allowing for good reception of the NOAA satellite. Using it this way also helps to null out strong vertically polarized stations. More information on the V-Dipole can be found on our previous post where we posted about Adam 9A4QV’s idea to use the V-Dipole for satellite reception.
2017: TV Antenna vs. NOAA Satellite
Also related to this post is a sneak preview on our new product: We’ve also caught onto the idea that TV antenna dipoles are extremely versatile, and are in the final stages of releasing a simple telescopic dipole product similar to the TV antenna used in this video. It will be released as an antenna set that comes with some portable mounting solutions like a suction cup and bendy tripod, and 3M of RG174 coax so that the antenna can be used anywhere. Target price is $10 -15 USD incl. shipping from China. This will probably also replace the stock telescopic whip antenna currently used in our dongle sets since the telescopic dipole is simply much more versatile.
About two weeks ago we posted our review of the Dreamcatcher, a new RTL-SDR and full ARM based computing platform built onto a single PCB. Back then the only OS available for it was a standard Armbian build, and no Outernet decoder was available. So we reviewed the Dreamcatcher with the Armbian OS and tested to see how well it worked as a general purpose RTL-SDR and computing platform.
Recently the Outernet team released a new build of ‘Skylark’ for their Dreamcatcher board. Skylark is their customized Outernet signal specific operating system that was available on the C.H.I.P. Skylark is essentially turnkey as it is much easier to setup and use. Just burn the image to an SDcard, insert the card, connect to the automatically generated Outernet WiFi hotspot on a PC or mobile device, and then browse to outernet.is to see the Skylark interface.
Unfortunately it is unclear how long some of the high bandwidth features such as the nice weather app may last. The Outernet Inmarsat L-band signal runs at a bandwidth of almost 20mB a day and appears to cost quite a bit of money to operate, so Outernet appear to be considering moving to a lower bandwidth signal in the near future. This will probably reduce content to data like text articles (news/APRS/Wikipedia/books) only. But even if it is text only it will still continue to be a very useful and interesting service.
Thank you to Silvia P. for writing in and letting up know about the SatNOGs “No-Rotator” project, which looks a lot easier to build compared to their motorized rotator. SatNOGs is an idea and organisation that is trying to make it easier to set up a low cost networked RF ground stations for monitoring various satellites. The idea is to increase satellite ground station coverage all over the world and collect and share received satellite data over the internet so that anyone in the world can view and make use of up to date satellite data.
An original SatNOGs station is built as a motorized antenna rotator, with directional antennas that point and track satellites as they pass over the ground station location. The gears and most internal plastic parts are 3D printed, with the rest of the items like bearings, frames and motors being available on eBay. The problem is that building the rotator is quite a big project, and takes a lot of research, purchasing and building to get started.
Recently over on their Wiki a new type of non-rotator ground station has appeared. The no-rotator ground station still consists of the basic SatNOGs electronics including an RTL-SDR and Raspberry Pi. But instead of using high gain directional motorized antennas this ground station uses a much simpler turnstile antenna tuned to about 137 MHz. Unlike the rotator, the turnstile probably doesn’t have enough gain to pick up some of the weaker amateur satellites, but should be good enough for NOAA/Meteor weather satellites and ISS APRS etc.
Over on his blog IK1XPV has been writing about his experiments in trying to create a new SDR which he calls the ‘BreadBoard RF103’. His SDR is based on a FX3 SuperSpeed Explorer Kit which is a development platform that has an ARM9 processor on board, USB 3.0 connectivity and various expansion headers. Connected to that board is an LTC2217 16-bit ADC which can sample at up to 105 Msps. An R820T2 is used as the tuning chip to enable reception from 30 – 1800 MHz, and reception from 0 – 30 MHz is handled in direct sampling mode. The R820T2 is the same chip used on most RTL-SDR dongles, as well as on the higher end Airspy. It is a very good tuning chip, but it is held back by the 8-bit ADC on the RTL2832U chip. So the 16-bit ADC on the LTC2217 should be able to really show it off.
BreadBoard RF103 Block Diagram
IK1XPV’s BreadBoard RF103 is currently running on HDSDR with 10 MHz of bandwidth. He writes that a modern and powerful PC with USB 3.0 is required to to handle all the data coming through. In the videos below he shows it receiving the FM band with what looks to be about 10 MHz of bandwidth.
HDSDR v2 76 ExtIO sddc dll SRate 8000000 OS 10 0 14393 CPU Intel Core i5 3350P @ 3 10G
BB103 VIDEOFM 012
So far the BreadBoard RF103 doesn’t seem planned to be a commercial device. The LTC2217 ADC is a $115 USD part, and the FX3 dev board is $49 USD. So while not a budget unit, it may still end up as as interesting SDR to home build and could contend with Airspy and SDRplay devices in the $100 – $300 USD range.
Over on YouTube a talk from the author of DSpectrum has been uploaded from his talk during the 13th Cyberspectrum Melbourne meetup. In his talk he goes through the full process of reverse engineering a wireless alarm system in DSpectrumGUI. DSpectrum is a reverse engineering tool that aims to make it trivial to demodulate digital RF transmissions using data captured from SDRs like an RTL-SDR or HackRF.
In the video he shows how to create a project, import a capture and create an overlay on Inspectrum and bring the waveform back into DSpectrum. DSpectrum was then able to automatically detect that the encoding used was PWM and convert it into a bit string. Then by importing multiple captures from various buttons on the alarm he shows how easy it is to see the differences in the bit strings from within DSpectrum. From these differences he uses DSpectrum to help identify what the function of each byte of the bitstring is. Finally he shows how to perform a replay attack with RFcat or similar hardware using the data gathered.
This is a really good talk to watch if you’re interested in getting started with reverse engineering simple digital signals, like those from ISM band devices.
Cyberspectrum Melbourne #13: Introduction to DSpectrum for reverse engineering signals
