Over on his blog author Manuel a.k.a ‘Tysonpower’ has written about a DIY Carbon Fibre Yagi antenna that he’s built for only 20€. The antenna is very lightweight thanks to a 12mm diameter carbon fibre pipe which is used as the main boom. It also uses 3D printed parts that clamp onto the carbon fibre pipe and hold the metal elements in place. The advantage of the carbon fibre pipe over a PVC one is not only is it lightweight and much easier to hold, but it also stronger, and much less bendy and floppy. The metal elements are welding rods which he found on eBay, and the carbon fibre pipe was sourced cheaply from China with Aliexpress.
A Yagi is a directional antenna with high gain towards the direction it is pointing. You’ll need to hand point the Yagi in the general direction of the satellite as it passes over, but you can expect much higher SNR readings compared to something like a QFH or Turnstile.
Manuel designed his antenna for 2M satellites (NOAA, Meteor M2, ISS etc), and was able to achieve over 36 dB SNR with an RTL-SDR.com V3 receiver, FM Trap and LNA4ALL on NOAA 18 at a 34° max. pass. He writes that the design is easily modifiable for other frequencies too.
To show off the design, construction and performance of his antenna he’s uploaded two videos to YouTube which we show below. The speech is in German, but even for non-German speakers the video is easily followed
UPDATE: Unfortunately we have been informed that the code base of this software was illegally decompiled and reused in an almost unchanged way from an already available closed source decoder. This means the program itself is illegal and totally unethical.
Please respect the original developers hard work and do not download this software.
A new STD-C Inmarsat decoder called —-Hz has recently been released. The decoder is Windows based and simply listens to the demodulated Inmarsat STD-C audio from a program such as SDR#. This means that it is compatible with the RTL-SDR, and any other SDR that can receive Inmarsat.
We gave the software a brief test and it ran very well, and managed to decode several SafeteNET messages without issue, maintaining a good lock most of the time. The author writes that he plans to improve on the software in the future by creating a web service based version of the software.
Currently there are two other Inmarsat decoders available. One is called InmarsatDecoder and the other is the Tekmanoid decoder. The InmarsatDecoder is generally regarded as the best, but the Tekmanoid decoder was recently updated for improved performance. The new software appears to be about the same as the Tekmanoid decoder.
Inmarsat STD-C messages are broadcast from geostationary satellites in the L-band at around 1.5 Ghz. They send mostly marine based messages such as the following quoted from the ——Hz website:
Safety: high seas, tropical storm warnings, ice accretion…
Shipping activity: moving oil rigs, submarine cable deployment and repairs…
Distress reports: MOB, ships lost at sea, migrant ship reports…
Military exercises (firing practice, no fly zones…)
Pirate at sea reports…
If you are interested in learning how to decode STD-C we also have a tutorial available here.
RF bypass for tuning from 24 – 1600 MHz – use as a regular RTL-SDR!
USB ports
GPIO forest
UARTs, I2C, SPI headers (unpopulated) for driving external hardware
Two microSD card holders – for boot and storage!
1 GHz CPU
256 MB RAM Now 512 MB RAM
USB wifi dongle (not shown) – STA+ AP mode capable!
Lots of LEDs! and Switches!
microUSB OTG
microUSB power port
Audio In/Out
Speaker with 1.4 W integrated audio amplifier
Fully mainline (4.10) Kernel and (2017.01) Uboot support! *** JST battery is being removed
On the Roadmap:
armbian/debian support
This is a fully-integrated SDR receiver – RF frontend, SDR, Compute, Wifi – Everything!
Outernet is an L-band satellite service that aims to be a download only “library in the sky”. Currently they are broadcasting from Inmarsat and Alphasat geostationary satellites which can be received from almost anywhere in the world. We have a tutorial on receiving and decoding their signal here. Every day almost 20 MB of data is sent down, and this includes data like news, weather forecasts, APRS, wikipedia articles, books and more. In the future you will be able to pay to upload private files or messages. This could be useful for sending messages to people isolated from cell phone reception, or for operating remote hardware.
Previously Outernet sold a DIY version of their receiver which included an RTL-SDR V3 or E4000 dongle, LNA+filter, a C.H.I.P embedded computer, and a patch antenna. Recently they have changed to their custom RTL-SDR hardware which is called the “SDRx”. The SDRx includes the RTL-SDR, LNA and filter on a single PCB. Over time it seems that they are moving in the direction of integration of all components onto a single PCB and this can be seen in the Dreamcatcher which now also includes the computing hardware. This is especially good news as the $9 C.H.I.P computing hardware has been almost impossible to acquire since its release.
The Dreamcatcher looks to be also not just useful for Outernet, but also for general projects that can be done on embedded hardware as there is a port which bypasses the L-Band filter.
Back in 2014 we posted about the XiOne. This was also to be an RTL-SDR and computing hardware built onto the same PCB. It would have been controlled via a WiFi connection and apps on a smart phone/tablet. Unfortunately the XiOne Indiegogo crowdfunding campaign never reached its target so the project faded away. The Dreamcatcher is somewhat similar in that both are RTL-SDRs with onboard computing hardware and WiFi connectivity.
The Dreamcatcher is not yet for sale, but it is currently under production. From the looks of the discussion on the forums, it looks like it will sell for $149 USD. Outernet have said that they are sending us a review sample, so keep an eye out for the review in the coming weeks.
The Outernet Dreamcatcher: RTL-SDR + LNA + Filter + Computing Hardware on a single PCB.
This software decoder appears to be an excellent choice for those people who want to perform their reception and decoding of Meteor M satellites all in Linux. Previously as explained in this previous post, you were able to receive the QPSK data in Linux with an RTL-SDR and a GNU Radio program, but then you’d still need to boot into Windows or run Wine to run LRPTofflinedecoder in order to generate the image. Now it appears that the image generation can be performed natively in Linux too with meteor_decoder. This help with creating portable automated Raspberry Pi based Meteor M decoder servers.
Meteor M is a class of Russian weather satellites that transmit live weather images of the earth as they pass over your location. They are somewhat similar to the NOAA satellites, although the Meteor satellites transmit higher quality images via a digital LRPT signal, rather than the analog APT signals used by NOAA. With an RTL-SDR, an appropriate antenna and decoding software they can easily be received.
An Example LRPT Image Received with an RTL-SDR from the Meteor M-N2 Satellite.
Over on his blog Lucas Teske has been comparing the LNA4ALL and an SPF5189 LNA from eBay on HRIT/LRIT reception from GOES satellites. SPF5189 LNA’s can be found on eBay for less than $8 USD, with free shipping from China, whereas the LNA4ALL costs 27 Euros shipped from Croatia. GOES is a geosynchronous orbit weather satellite which requires a satellite dish or other high gain antenna to receive. It downlinks at about 1.7 GHz, which means that a high quality LNA with low noise figure and good PCB design is needed for reception.
In his post Lucas mentions how he saw a review on eBay stating that the SPF5189 did not work at L-band. However, he found that odd as all of his SPF5189 LNA’s seemed to work just fine with L-band reception. So he did a benchmark comparing the SPF5189 to the PSA5043+ based LNA4ALL which is known to work well on L-band.
From his comparisons he found that the SPF5189 does indeed work well on L-band, and is comparable to the LNA4ALL. He concludes that the reviewer must have received a bad unit, or didn’t know what he was doing.
Lucas also makes an important note regarding the PCB design of these LNA’s. Even though the SPF5189 and PSA5043 chips have similar specs, with LNA’s the design of the PCB is crucial, as a poor design can significantly degrade performance. With the LNA4ALL you can be sure that the design is good, although the SPF5189 LNA’s currently on eBay look to be designed okay as well. Though with some eBay sellers there is no guarantee that you will receive a good board. We note that we have seen some really poor designs for PSA5043 LNA’s out there as well.
Over on his blog USA-Satcom has released his XRIT (LRIT/HRIT) decoder for GOES satellites. The software requires a licence and costs $100 USD. GOES-13 (East), GOES-15 (West) and the new GOES-16 are geosynchronous orbiting satellites that broadcast very nice high resolution weather images of the entire visible disk of the earth. The transmit their LRIT/HRIT signals at about 1.7 GHz at fairly weak power, which means that a good LNA and dish set up is critical to be able to receive them. A dish size of about 1 meter, or an equivalent grid or Yagi is recommended as the lowest starting point.
GOES Full Disk Image of the Earth
USA-Satcom’s decoder is Windows based and comes with a nice GUI. Some portions of the code are based on the Open Satellite Project created by Lucas Teske. It currently supports the Airspy R2/Mini and the SDRplay RSP2 software defined radios.
The software is not free, it costs $100 USD for the licence. To help curb illegal distribution of his software which has been rampant in the past, USA-Satcom also requests that you show some proof of a working setup which is capable of receiving the GOES signal before inquiring about the software.
If you are also interested, USA-Satcom did an interesting talk at Cyberspectrum a few months ago, and he has also recently uploaded his slides.
LilacSat-1 is an educational CubeSat built by students from the Harbin Institute of Technology (HIT) in China. It was recently launched from the ISS on 25 May 2017 as part of the QB50 science experiment to explore the lower thermosphere, and it is expected to stay in orbit for about 3 months. Apart from BPSK telemetry at 145.935 MHz, LilacSat-1 is interesting because it contains on board an FM to Codec2-BPSK digital voice amateur radio transponder at 145/436 MHz (uplink/downlink). It is probably the first amateur radio satellite to contain an FM to digital voice transponder.
To decode LilacSat-1 digital voice and telemetry you can use a Linux live CD provided by HIT, or download the GNU Radio decoder directly from the LilacSat-1 information page on the HIT website. The GNU Radio program can be used with any GNU Radio compatible SDR, such as an RTL-SDR.
An example of LilacSat-1 being decoded has also been uploaded by YouTube by Scott Chapman. In his test he used an RTL-SDR to work the pass live, but in the video shows an offline decoding received by his SDRplay which was also monitoring the same pass.
Recently Outernet released their new ‘Dreamcatcher’ hardware which is an RTL-SDR + L-band LNA & filter + computing board all on the same PCB. The Dreamcatcher costs $99 USD and can be bought directly from their store. For your $99 you get the Dreamcatcher board, as well as a new ceramic L-band patch antenna which has a built in L-band LNA and filter. The built in LNA is useful as it allows you to use a few meters of extension cable in order to get the patch antenna in a good position outdoors.
At the moment the Dreamcatcher can be run with two different SD card images: the Skylark Outernet software, or Armbian (Linux). The Armbian image is basically just standard Armbian and at the moment does not actually run any Outernet software, and cannot decode their signal – but this is being worked on. Eventually they hope to depreciate the Skylark image and instead use an Outernet receiver app that runs on Armbian.
When running on the standard Armbian image, the Dreamcatcher can be used as a regular RTL-SDR connected to Linux, as there is a bypass port which bypasses the built in L-band LNA and filter. This port is enabled by default, but can be software switched to the L-band port if desired. There is also a 4.8V bias tee on the bypass port that can be turned on in software and used to power external devices via the coax cable. Currently there is no display support on the Dreamcatcher so the unit must be run headless, meaning that you must connect to it via UART or SSH from another PC.
The Outernet Dreamcatcher
The Dreamcatcher is advertised with the following specifications:
L-band SAW filter (1525 – 1559 MHz)
Two-stage L-band LNA with 34dB gain
1 PPM TCXO
RF bypass for tuning from 24 – 1600 MHz – use as a regular RTL SDR!
Software switchable bias tee
3 USB ports
GPIO forest
UARTs, I2C, SPI headers (unpopulated) for driving external hardware
Two microSD card holders – for boot and storage!
1 GHz CPU
512 MB RAM
USB wifi dongle (based on RTL8188CUS chipset) – AP mode capable!
Lots of LEDs!
Switches!
microUSB OTG
microUSB power port
Audio In/Out
Fully mainline (4.10) kernel and Uboot (2017.01) support!
Also as explained on the forums, Dreamcatcher uses an Allwinner A13 SoC, which has inside an ARM Cortex A8 @ 1 GHz CPU. They’ve also added 512MB of RAM. The PCB measures 12 cm x 12 cm.
Currently the Dreamcatcher is being advertised as beta hardware, as they give the following warning:
Although some assistance can be found on our forums, Outernet provides no direct support for this product. If you are not a tinkerer, hobbyist, or hardware hacker, you may be disappointed with your purchase.
The Dreamcatcher also comes with Outernet’s latest L-band patch antenna. The new patch antenna uses a ceramic patch and a 12 cm x 12 cm PCB ground plane. The antenna is ‘active’, as it has a built in L-band LNA and filtering. It is powered by the bias tee on the Dreamcatcher, and can also be powered by the bias tee on our V3 RTL-SDR’s. An active antenna is a good idea as this allows you to place the antenna outdoors (you’d need to waterproof this antenna in a plastic box though), and run a coax cable inside. The LNA should help overcome the coax cable loss which can be quite high at the L-band Outernet frequency of 1.5 GHz.
Outernet has provided us with a sample of this kit, and we plan to release a full review of the unit within the next few weeks.
Outernet active ceramic patch antenna (Front)Outernet active ceramic patch antenna (Rear)
Last week we posted about Outernet’s new Dreamcatcher unit which is an RTL-SDR + L-band LNA + computing board all on the same PCB. The Dreamcatcher comes with a new active ceramic L-band patch antenna, costs $99 USD (plus shipping) and can be bought directly from their store. Outernet were kind enough to send us a review unit, and we’ve been testing it for the past few weeks. This post is a review of the unit.
Background
Outernet is a free data service that uses L-band satellites to beam down information like news, weather updates, Wikipedia articles, books and more.
In the past Outernet have used the $9 USD C.H.I.P computing board, an RTL-SDR dongle and an external LNA as the receiving hardware for their data service. However, popularity of the Outernet service has been severely hindered by the huge supply shortages of the C.H.I.P. Over the past year or so it has been almost impossible to get a hold of a C.H.I.P unit if you did not back the Kickstarter or buy one from Outernet’s first initial stock. By manufacturing their own PCB including the computing hardware, Outernet must be hoping to be able to control their stock situation, and not rely on third parties who may not be able to deliver.
At the moment the Dreamcatcher can only be run on their new Armbian image. The older Skylark image has been removed from their servers presumably because the Outernet signal is going to change in the near future and the old demodulator on Skylark may no longer work. The Armbian image is basically just standard Armbian and at the moment does not actually run any Outernet software, and cannot decode their signal, but this is being worked on. Eventually they hope to replace Skylark with a standard decoding app that runs on Armbian.
In this post we’ll review the Dreamcatcher with Armbian and consider it as a general purpose receiver (not just for Outernet), and we’ll also review the new active ceramic patch antenna as well.
Dreamcatcher Overview
The Dreamcatcher is a single PCB that combines an RTL-SDR, Linux (Armbian) based computing hardware, and an L-band LNA and filter.
On first impressions we noticed that the PCB is relatively large square at about 12 cm by 12 cm. The most prominent chip is the Allwinner A13 SoC. The RTL-SDR circuitry is positioned in the upper right with the RF sections (R820T and LNA) both covered with RF shielding cans. There is no onboard WiFi circuitry, but a small ‘EDUP’ branded WiFi dongle is included and plugs into one of the USB ports on the PCB.
We measured the Dreamcatcher to be using about 400 mA – 600 mA while idle and 800 mA while utilizing the RTL-SDR and 100% CPU. Heat is not an issue as the Dreamcatcher stays relatively cool during its operation even at 100% CPU with the CPU only getting up to about 45 degrees C.
Computing and Ports
The Dreamcatcher uses an AllWinner A13 System on Chip (SoC). Inside the AllWinner A13 is a single core ARM Cortex A8 CPU @ 1 GHz. The hardware is very similar to the hardware used on the C.H.I.P. Onboard the PCB is 512 MB of RAM, and there no onboard flash so everything is stored on an SD card.
There is space for two SD card slots on the board. One SD card is used for the Armbian Linux image, and the other can be used for data storage. There are also three USB-A ports available, but one is used up by the included WiFi dongle. There is one micro USB port for USB OTG and the another for power only. The USB OTG port can be used for the initial setup of the board, before it is connected to WiFi.
There are also audio and microphone input jacks available, breakout expansion pads for advanced users and some power/reset and boot setting switches.
RF Hardware
On board the PCB is circuitry for a single R820T2 based RTL-SDR with 1PPM TCXO. There are two SMA RF ports. One port is connected to the L-band LNA and filter which is to be used for Outernet or other L-band satellite reception with a passive patch antenna. The L-band port uses a 34dB gain LNA with L-band filter with a pass band of 1525 – 1559 MHz.
The other SMA port bypasses the LNA + filter so that the Dreamcatcher can be used as a general purpose RTL-SDR as well. A software controllable silicon switch is used to bypass the LNA + filter, so only one port can be used at a time. The bypass port also has a software switchable 4.8V bias tee which can be used to power the new active ceramic patch antenna from Outernet.
Dreamcatcher Setup
Setting up the Dreamcatcher involves burning their latest Dreamcatcher Armbian image to a microSD card, inserting the card, and then completing the setup via the UART connection. The full setup instructions are detailed in the image readme.txt file and in their operating manual available here. Various code snippets that show how to turn on the bias tee for example can be found here.
The full setup might take about 10 – 15 minutes, including burning the SD card. Once setup the Dreamcatcher should be connected to your WiFi connection, and then if you prefer you can SSH into it from a PC on your network using PuTTY or any other SSH software.
There are two ways to set up the UART connection on the Dreamcatcher. The first is to use the USB OTG port, and the second is to use a $1-$2 USB to UART adapter. The easiest is to use the USB OTG connection. To use it fist burn the image to an SD card, and then connect a USB cable from the USB OTG port on the Dreamcatcher to a USB port on your PC. The Dreamcatcher will be powered through the OTG port, and once the Dreamcatcher boots it will show up as a serial port on your PC. Now you can use a program like PuTTY to connect to that serial port.
The steps for using PuTTY to connect to the board are shown below.
Connect your USB to UART adapter to the UART1 pins, or the USB OTG port to your PC with a cable. If using USB OTG power the unit on now.
Now determine the COM port that you’re USB to UART adapter or USB OTG cable has been assigned by looking for the device in Device Manager.
Next in PuTTY choose “Serial”, enter the assigned COM port and set the baud rate to 115200. Then click Connect.
If using USB OTG the login prompt will now show. If using the UART adapter you can power up your Dreamcatcher and text should immediately begin scrolling in PuTTY. Wait for it to boot and reach the login prompt.
Now follow the instructions in the readme.txt file to setup the user accounts, and connect to WiFi.
The Outernet Armbian image comes with no software preinstalled, so after you login you’ll need to install the RTL-SDR drivers, and whatever software you want to run on it.
Dreamcatcher login on UART
Dreamcatcher Testing
Basic Software
First we tested the Dreamcatcher with some simple software like rtl_adsb which is automatically installed during the RTL-SDR install process. The first step was to connect an antenna to the LNA_bypass port. The bypass port is enabled by default, so no extra commands are needed to enable it. rtl_adsb was able to pick up aircraft with no problems.
Next we installed dump1090 and repeated the test. Again planes were picked up with no trouble. We also tested the dump1090 webserver, and we were easily able to connect to it from a networked PC.
Next we tested rtl_fm to see if we could get some audio out of the headphone jack. First we had to install sox with ‘apt-get install sox’. Then by default the volume is muted and turned down to zero so to unmute it, type in ‘alsamixer’. Use the arrow keys and the ‘m’ key to select all the devices and unmute them. Also turn up the volume on the power amplifier. With the sound unmuted rtl_fm ran well and could drive a speaker fairly loudly. The command we used was ‘rtl_fm -M wbfm -f 89.1M | play -r 32k -t raw -e s -b 16 -c 1 -V1 -‘
We also tested other software like rtl_433 which had no trouble running.
Currently Outernet have set up Howto’s for several applications including ADS-B, listening to FM broadcasts, setting up an APRS iGate, setting up Tight VNC which allows a networked graphical display, setting up YAAC APRS on Tight VNC, setting up WSPR reception, and using rtl_power for wideband spectrum analysis.
GR-Iridium & L-Band
We also tested gr-iridium on the Dreamcatcher which is software that allows you to listen to L-Band Iridium satellite phone calls and data. To actually get it to install we had to first set the Armbian package manager from Jessie to Stretch. This allowed us to download and install the latest version of GNU Radio from apt-get which is required for installing gr-iridium.
For reception we couldn’t use the new ceramic patch antenna because the SAW filter cut off is 1559 MHz and Iridium is at around 1625 MHz. Instead we used an LNA4ALL and the older Outernet metal patch antenna. We also tested the metal patch antenna with the onboard L-band LNA and this worked as well, although this is more difficult to use as a longer extension coax cable can’t be used unless you want lots of signal loss (since the LNA is not near the antenna). Iridium signals are often strong enough to be picked up even with a simple dipole, so that could work too if you can’t obtain a patch antenna.
We were able to get gr-iridium to run at 1 MSPS, but we ran into CPU limitations at anything higher which is unfortunate as gr-iridium really needs the bandwidth to cover as much of the Iridium band as possible. However, even with only 1MSPS we were able to receive and decode a very short 2 second call.
Unfortunately there is no software available for the Outernet signal or Inmarsat signals at the moment on Armbian, so we were unable to test these signals. Also JAERO for AERO signals is available for openSUSE 42.3, but not yet available on Debian systems. If anyone knows of any other Linux compatible L-band signal decoders please let us know in the comments. Outernet are planning to release an Armbian based decoder for their satellite service in the future.
Radio Data Streaming Software
Unfortunately, we started to run into some trouble when it came to running RTL-SDR streaming server software like rtl_tcp, SpyServer and OpenWebRX. In short none of those would work very well by default, however some tweaks were able to improve the situation.
With rtl_tcp we were only able to achieve stutter free operation at a 0.25 MSPS data rate. In comparison a Raspberry Pi 3 connected to the same WiFi network was able to easily handle at least 1 MSPS. It turns out that the ‘EDUP’ WiFi dongle that is included with the Dreamcatcher is quite slow, despite supporting 802.11n. Changing to a higher quality WiFi dongle allowed us to stream smoothly at 1 MSPS. The Outernet team have also reported to us that using an Ethernet adapter allows smooth streaming at 2.4 MSPS.
Next we tried the new SpyServer streaming software which is designed for Airspy SDRs, but also works with RTL-SDRs. The first problem we ran into was that the public SpyServer download did not run on the Dreamcatcher. We had to ask the SpyServer developer for a special version that was compiled for older CPUs. Once running SpyServer we sadly found that it would not run smoothly at any sample rate, with or without full IQ used. SpyServer uses less bandwidth compared to rtl_tcp, but here the problem was high CPU usage. The SpyServer does a lot of computations on the server side so the CPU usage is quite high. Unfortunately the CPU on the Allwinner A13 seems to be not powerful enough to run SpyServer.
We also tried OpenWebRX which is used for efficient remote streaming. See sdr.hu for various OpenWebRX SDRs shared on the internet. To save bandwidth OpenWebRX only sends waterfall data and compressed audio instead of full IQ data. But even at 0.25 MSPS the Dreamcatcher’s CPU struggled and was stuck at 100% CPU usage using the default config file. After tweaking the config file a little we were able to achieve smooth results at 1 MSPS, but only for one connection. Andras, the creator of OpenWebRX is working on some code optimizations for the Dreamcatcher which may improve performance in the future.
We think OpenWebRX might have trouble running on the Dreamcatcher’s Cortex A8 as it is a single core CPU, and OpenWebRX runs several threads. In comparison a Raspberry Pi 3 ran OpenWebRX easily and total CPU usage remained under 50%. This is because the Pi3 has a Cortex A53 @ 1.2 GHz, which is a 4 core CPU.
To get a handle on the CPU performance differences between the Pi 3 and Dreamcatcher CPU’s we ran sysbench on single thread, and on 4 thread mode using: ‘sysbench –test=cpu run’ and ‘sysbench –test=cpu –num-threads=4 run’.
Sysbench Dreamcatcher (1 Thread) – 286.584s
Sysbench Dreamcatcher (4 Threads) – 286.8299s
Sysbench RPi3 (1 Thread) – 182.3092s
Sysbench RPi3 (4 Threads) – 45.7500s
Sysbench shows that the Pi 3 is quite a bit faster, especially if all four cores can be utilized.
The Ceramic Active Patch Antenna
We also tested Outernet’s latest iteration of their L-band patch antenna. This new patch antenna uses a ceramic dielectric instead of an air gap which was used on their previous metal patch antenna. These ceramic patches are similar to the ones used in small GPS antennas, but larger.
The new patch antenna is also ‘active’, meaning that it has built into it a low noise amplifier (LNA) which must be powered via a 3-5V bias tee. The Dreamcatcher RF_bypass port has the required 4.8V bias tee to make it run. An L-band SAW filter is also built into the circuit and we assume the pass range (1525 – 1559 MHz) is the same as the filter used on the Dreamcatcher L-band port.
This new active patch antenna is a good idea as it allows you to use a run of a few meters of coax cable to get the antenna outside and into a good position where it can see the satellite.
We compared the new active ceramic patch with the previous metal patch + Outernet LNA combo using an RTL-SDR Blog V3 dongle with the bias tee powering the LNAs on both antennas. Signal levels were about 1-2 dB’s lower on the ceramic antenna, but we observed that the ceramic patch was slightly less directional and easier to point. We also tested with 2.5 meters of thin lossy RG174 coax and didn’t notice any loss in SNR. The LNA helps to boost the signal, so that signal losses in the coax are negligible.
Again, one issue with these antennas is that they have no mounting solution so we simply glued a 1/4 inch female thread onto the back of the PCB, and then used a standard camera suction cup to mount it on a window with a good view of the Inmarsat satellite. The antenna circuitry on the back is also not waterproof, so to waterproof the antenna it was later covered with a plastic sandwich bag. People who want to mount it more permanently might consider using a plastic lunchbox or other sturdier solution.
Active Ceramic Patch Antenna
Active Ceramic Patch Antenna (Rear) w/ our custom mount glued on
Active Ceramic Patch Antenna w/ our custom mount on window
Ceramic Patch
Ceramic Patch w/ 2.5M Extension
Metal Patch w/ Outernet LNA
Metal Patch w/ Outernet LNA & 2.5M Extension
Conclusion
So is the Dreamcatcher worth it? For $99 USD (plus shipping) about you’re getting a fully assembled compute board with RTL-SDR and L-Band LNA+filter module built in, as well as an active ceramic antenna. It is the first computing board that we know of that includes an RTL-SDR on the PCB itself. In the past projects like the XiOne attempted something similar, but never got off the ground.
Consider that a Raspberry Pi 3 costs $35, an RTL-SDR capable of receiving L-band like the V3 costs $20 and an Nooelec/Outernet L-Band LNA+SAW filter module costs $17.95. The Outernet metal patch antenna no longer seems to be for sale but that used to cost $25. The total price of those individual components adds up to $97.95 USD.
The Dreamcatcher is still a bit buggy, with problems regarding the streaming server RTL-SDR apps. And compared to the Pi 3 the CPU performance is quite a bit less, meaning that high CPU use software like OpenWebRX does not function that well. But regular apps that can run on the device like dump1090, rtl_433 etc all run just fine. In the future we’d like to see a more powerful CPU used as this would allow several more applications to run smoothly on the board.
In terms of product maturity, Outernet have put up a warning for potential buyers on their store which notes that the Dreamcatcher is “only for tinkerers, hobbyists and hardware hackers”, and that “no direct support for it is provided”. The most assistance available will be on their forums. To actually use the board you will need a decent understanding of Linux (being able to install and run software from the terminal), and preferably you’d need some previous experience with other small computing boards like the Raspberry Pi.
All in all the Dreamcatcher is a great buy for someone looking to get an all-in-one device, but it is still more suited to advanced experimenters. Hopefully the board soon matures, and we start to see actual Outernet apps appearing, as well as potential upgrades to the hardware as this will push the value of the board up significantly.
Over on his YouTube channel Adam 9A4QV has uploaded a video that shows him receiving the NOAA 19 HRPT signal at 1698 MHz with his HackRF, LNA4ALL and the simple circularly polarized cooking pot antenna that we saw in his last videos.
HRPT stands for High Resolution Picture Transmission and is a digital protocol that is used on some satellites to transmit much higher resolution weather images when compared to the APT signal that most people are familiar with receiving. The HRPT signal is available on NOAA19, which also transmits APT. However, unlike APT which is at 137 MHz, HRPT is at 1698 MHz, and is typically a much weaker signal requiring a higher gain motorized tracking antenna.
However in the video Adam shows that a simple cooking pot antenna used indoors is enough to receive the signal (weakly). The signal is probably not strong enough to achieve a decoded image, but perhaps some tweaks might improve the result.
Over on his Reddit thread about the video Adam mentions that a 90cm dish, with a proper feed and two LNA4ALLs should be able to receive the HRPT signal easily. User devnulling also gives some very useful comments on how the software side could be set up if you were able to achieve a high enough SNR.
GNU Radio has HRPT blocks in the main tree (gr-noaa) that work well for decoding and then David Taylor has HRPT reader which will generate an image from the decode GR output. http://www.satsignal.eu/software/hrpt.htm
http://usa-satcom.com has a paid HRPT decoder that runs on windows that has some improvements for lower SNR locking and works very well.
– devnulling
On a previous post we showed @uhf_satcom‘s HRPT results where he used a motorized tracking L-band antenna and HackRF to receive the signal. Some HRPT image examples can be found in that post.
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.
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.
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.
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.
Back in June we tested Outernet’s new Dreamcatcher which is an ARM based computing board with RTL-SDR and L-band LNA built in. The $99 USD kit also included an external active L-band patch antenna. The Dreamcatcher full kit has now been reduced to $89 USD, and the active L-band patch antenna can also now be purchased by itself for $29 USD. The active patch antenna is also compatible with the bias tee on our V3 dongles and is a good low cost option for exploring most L-band satellite signals like Outernet, Inmarsat STD-C and AERO around 1542 MHz. The filter does unfortunately cut off the higher Iridium frequencies though.
They are also selling off their older L-band SDRx RTL-SDR boards at a reduced price of $20 USD. The SDRx is a RTL-SDR PCB with a built in L-band LNA and filter, but unlike the Dreamcatcher does not have built in computing hardware. They also have a limited $25 USD edition version of their active patch antenna which includes a built in RTL-SDR. This version is a bit more noisy compared to the standard active patch, but may be an interesting experimental antenna for some.
Leandvb is command line based lightweight DVB-S decoder designed for receiving Digital Amateur TV, including signals like HamTV from the International Space Station. The RTL-SDR can be used together with leandvb and it turns out that leandvb can also be used to decode the Outernet signal. If you were unaware, Outernet is a free L-band based satellite service that provides content such as news, weather data, APRS repeats and more. Currently you can get about 20MB of data a day. Outernet receivers are also all based around the RTL-SDR, allowing for very cheap receivers to be built. At the moment you’ll need a C.H.I.P or their specialized Dreamcatcher hardware to run their special Skylark OS with software decoder, but a general Armbian decoder is in the works.
Alternatively leandvb can be used, and over on their website the folks behind the leandvb software have uploaded a tutorial showing how to use leandvb to decode Outernet. Thanks to some reverse engineering attempts by Daniel Estévez, it was discovered that the Outernet modulation is very similar to DVB-S so the standard decoder can be used with some custom flags. Leandvb only outputs raw frames, not decoded data. They haven’t tested it, but it may be possible to feed the frames into Daniel Estevez’s free-outernet project for obtaining the final files.
During the testing they also discovered some interesting notes about the E4000 and R820T RTL-SDRs. For example by patching the R820T2 drivers to add some additional VGA gain they were able to make the R820T2 chips more sensitive at the Outernet frequency compared to the E4000 chip by bringing the signal further out of the quantization noise. They also tested a 60cm dish vs a patch antenna and found that the dish works significantly better.
Manuel a.k.a ‘Tysonpower’ has been using his RTL-SDR (and his Baofeng) to listen in on ARISS contacts from the International Space Station (ISS). ARISS stands for Amateur Radio on the ISS, and is a program often used by schools to allow students to contact and ask questions to astronauts on the ISS with a ham radio. It is possible for anyone to listen in on the downlink (astronaut speech) if the ISS is over your location while transmitting. The uplink however may not be able to be heard as the signal is directed upwards towards the station.
For his first try he used a Baofeng (cheap Chinese handheld) and a DIY Carbon Yagi. For the second contact he used his RTL-SDR V3, an FM Trap and an LNA4ALL on a V-Dipole antenna placed on the roof of his car. With this set up he was able to receive the downlink transmissions from 1.6 degrees to 1.3 degrees elevation.
Bitcoin is the worlds first and most popular digital currency. It is steadily gaining in value and popularity and is already accepted in many online stores as a payment method. In order to use Bitcoin you first need to download a large database file called a ‘blockchain’, which is currently at about 152 GB in size (size data obtained here). The blockchain is essentially a public ledger of every single Bitcoin transaction that has ever been made. The Bitcoin software that you install initially downloads the entire blockchain and then constantly downloads updates to the blockchain, allowing you to see and receive new payments.
Blockstream is a digital currency technology innovator who have recently announced their “Blockstream satellite” service. The purpose of the satellite is to broadcast the Bitcoin blockchain to everyone in the world via satellite RF signals, so that even in areas without an internet connection the blockchain can be received. Also, one problem with Bitcoin is that in the course of a month the software can download over 8.7 GB of new blockchain data, and there is also the initial 152 GB download (although apparently at the moment only new blocks are transmitted). The satellite download service appears to be free, so people with heavily metered or slow connections (e.g. 3G mobile which is the most common internet connection in the third world/rural) can benefit from this service as well.
The service appears to be somewhat similar to the first iteration of the Outernet project in that data is broadcast down to earth from satellites and an R820T RTL-SDR is used to receive it. The blockstream satellite uses signals in the Ku band which is between 11.7 to 12.7 GHz. An LNB is required to bring those frequencies back down into a range receivable by the RTL-SDR, and a dish antenna is required as well. They recommend a dish size of at least 45 cm in diameter. The signal is broadcast from already existing satellites (like Outernet they are renting bandwidth on existing satellites) and already 2/3 of the earth is covered. The software is based on a GNU Radio program, and can be modified to support any SDR that is compatible with GNU Radio. They write that the whole setup should cost less that $100 USD to purchase and set up.
To set it up you just need to mount your satellite antenna and point it towards the satellite broadcasting the signal in your area, connect up your LNB and RTL-SDR and then run the software on your PC that has GNU Radio installed.
More details can be found on the Blockstream Satellite website, and technical details about the software and hardware required can be found on their GitHub page.
How the Blockchain satellite works (From blockstream.com/satellite/howitworks/)
Some may wonder what’s the point if you can’t transmit to the service to make payments with it. Over on this Bitcoin Reddit thread user “ideit” explains why it’s still useful in this nice quote.
You sell goats in a small village. A customer wants to buy a goat, but you have no banks so people have put their money into bitcoin. Your customer goes to the village center which has a few computers hooked up to the internet. He sends you payment then comes to get his goat. You don’t have internet near your goat farm, but you’re connected to the satellite so you can see he sent you payment and you give him his goat.
Or, you live in an area that caps your bandwidth. You want to run a full node, but downloading blocks eats away at your cap. Connecting to a satellite reduces your bandwidth usage.
Or, you’re using an air gapped laptop to sign transactions from your wallet for security reasons. You can now connect that laptop to the satellites so your laptop can generate its own transactions without connecting to the internet.
Or, your internet connection is terrible. You can usually broadcast transactions since they’re small, but downloading blocks and staying in sync with the blockchain is literally impossible. Connect to a satellite and now it’s simple.
Over on his YouTube channel Adam 9A4QV has uploaded a video that shows him receiving the NOAA 19 HRPT signal at 1698 MHz with his HackRF, LNA4ALL and the simple circularly polarized cooking pot antenna that we saw in his last videos.
HRPT stands for High Resolution Picture Transmission and is a digital protocol that is used on some satellites to transmit much higher resolution weather images when compared to the APT signal that most people are familiar with receiving. The HRPT signal is available on NOAA19, which also transmits APT. However, unlike APT which is at 137 MHz, HRPT is at 1698 MHz, and is typically a much weaker signal requiring a higher gain motorized tracking antenna.
However in the video Adam shows that a simple cooking pot antenna used indoors is enough to receive the signal (weakly). The signal is probably not strong enough to achieve a decoded image, but perhaps some tweaks might improve the result.
Over on his Reddit thread about the video Adam mentions that a 90cm dish, with a proper feed and two LNA4ALLs should be able to receive the HRPT signal easily. User devnulling also gives some very useful comments on how the software side could be set up if you were able to achieve a high enough SNR.
GNU Radio has HRPT blocks in the main tree (gr-noaa) that work well for decoding and then David Taylor has HRPT reader which will generate an image from the decode GR output. http://www.satsignal.eu/software/hrpt.htm
http://usa-satcom.com has a paid HRPT decoder that runs on windows that has some improvements for lower SNR locking and works very well.
– devnulling
On a previous post we showed @uhf_satcom‘s HRPT results where he used a motorized tracking L-band antenna and HackRF to receive the signal. Some HRPT image examples can be found in that post.
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.
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.
