Tagged: satellite

Outernet 3.0: Implementation Details and a 71,572km LoRa World Record

Outernet Dreamcatcher Board running with an LNB
Outernet Dreamcatcher Board running with a cheap satellite TV LNB

Outernet 3.0 is gearing up for launch soon, and just today they've released a blog post introducing us to the RF protocol technology behind the new service. If you weren't already aware, Outernet is a free satellite based information service that aims to be a sort of 'library in the sky'. Their aim to to have satellites constantly broadcasting down weather, news, books, radio, web pages, and files to everyone in the world. As it's satellite based this is censorship resistant, and useful for remote/marine areas without or with slow/capped internet access.

Originally a few years ago they started with a 12 GHz DVB-S satellites service that gave 1GB of content a day, but that service required a large dish antenna which severely hampered user adoption. Their second attempt was with an L-band service that only needed a small patch antenna. This service used RTL-SDR dongles as the receiver, so it was very cheap to set up. Unfortunately the L-band service had a very slow data rates (less than 20MB of content a day), and leasing an L-band transmitter on a satellite proved to be far too expensive for Outernet to continue with. Both these services have now been discontinued.

Outernet 3.0 aims to fix their previous issues, giving us a service that provides over 300MB of data a day, with a relatively cheap US$99 receiver that is small and easy to set up. The new receiver uses a standard Ku-Band LNB as the antenna, which is very cheaply available as they are often used for satellite TV reception. The receiver itself is a custom PCB containing a hardware (non-SDR based) receiver with a LoRa decoder.

LoRa is an RF protocol that is most often associated with small Internet of Things (IoT) devices, but Outernet have chosen it as their satellite protocol for Outernet 3.0 because it is very tolerant to interference. In Outernet 3.0 the LNB is pointed directly at the satellite without any directive satellite dish, meaning that interference from other satellites can be a problem. But LoRa solves that by being tolerant to interference. From the uplink facility to the satellite and back to their base in Chicago the LoRa signal travels 71,572 km, making it the longest LoRa signal ever transmitted.

According to notes in their forums Outernet 3.0 is going to be first available only in North America. Europe should follow shortly after, and then eventually other regions too. When ready, their 'Dreamcatcher 3.0' receiver and computing hardware is expected to be released for US$99 on their store. You can sign up for their email list on that page to be notified upon release.

Also as a bonus, for those interested in just LoRa, the Dreamcatcher 3.0 is also going to be able to transmit LoRa at frequencies anywhere between 1 MHz to 6 GHz, making it great for setting up long range LoRa links. This might be an interesting idea for hams to play with.

The Outernet 3.0 'Dreamcatcher' Receiver.
The Outernet 3.0 'Dreamcatcher' Receiver.

December High Powered Rocket Flight with RTL-SDR used for GPS Measurements

The rocket carrying the RTL-SDR.
The rocket carrying the RTL-SDR.

Back in April and July of last year we posted about Philip Hahn and Paul Breed's experiments to use an RTL-SDR for GPS logging on their high powered small rockets. Basically they hope to be able to use an RTL-SDR combined with a computing platform like a Raspberry Pi or Intel Compute stick and software like gnss-sdr to record GPS data on their rocket. Using an RTL-SDR would get around the COCOM limits that essentially stop GPS from working if it measures faster than 1,900 kmph/1,200 mph and/or higher than 18,000 m/59,000 ft.

In the past they've been able to get usable data from the flights, but have had trouble with reliability and noise. That said they also tried commercial GPS solutions which have also failed to work properly even on flights travelling under the COCOM limits, whereas the RTL-SDR actually got data that could still be post processed.

On their latest flight they still had trouble with the RTL-SDR GPS solution working live during flight, but RF GPS data was still recorded and post-processing the data with SoftGNSS yielded results again as in their previous trials. The post goes over the more details and provides the raw RF data to play with if you want to have a go at extracting the data yourself.

If you are interested in a full summary of Phillip and Paul's experiments, then the GNU Radio blog has a nice summary written by Phillip that explains their full journey of trying to get a working RTL-SDR based GPS system for their rockets.

Rocket Trajectory as measured by the RTL-SDR based GPS receiver.
Rocket Trajectory as measured by the RTL-SDR based GPS receiver.

Outernet 3.0 Coming Soon: Free 30kbps – 100kbps satellite data downlink for news, weather, audio etc

The new Outernet Dreamcatcher v3.01
The new Outernet Dreamcatcher v3.01

Over the past few years we've posted quite a bit about Outernet who offered a free downlink of satellite data such as news, Wikipedia articles and weather updates that was able to be received with a small L-band patch antenna, LNA and an RTL-SDR dongle.

Recently we've seen news on their forums that Outernet is planning on discontinuing their L-band service, and instead opening up a new much more efficient Ku-band service. Unfortunately that means that RTL-SDRs and the previous Outernet L-band hardware will no longer be useful for the downlink, but the new service appears to offer several significant advantages.

Firstly the downlink data rate is much higher at 30kbps, with the plan to eventually go up to 100kpbs. That's 300MB - 1 GB a day which is a lot more compared to the previous L-band implementation that gave less than 20MB a day.

Secondly the hardware seems to be simplified as well. All that is needed is their new Dreamcatcher V3 receiver board and a small Ku-band LNB (11.7-12.75 GHz). They claim that no dish is required as the LNB pointed at the satellite by itself will work just fine. The first iteration of Outernet also used Ku-band satellites, but required a large dish antenna to receive it which was a major hurdle to user adoption. They now appear to have discovered a new way to broadcast in the Ku-band without the need for a dish.

Thirdly, moving to Ku-band means significant cost savings for Outernet allowing them to survive and continue with their free data service. From what we understand the L-Band satellite downlink service is extremely costly to run, whereas a Ku-band service is much cheaper. There are also cost savings for the user as Ku-band LNBs are very common hardware that can be found cheaply for $10 - $20 US.

About the new services that they can offer and the cost savings that they can achieve Syed the CEO of Outernet writes:

The fatter pipe [300MB - 1GB] makes a lot of things possible, one of which is a true radio broadcast. How about a national radio broadcast that isn't SiriusXM? Our new receiver will include a speaker; audio through the speaker while files download in the background. But more data is not the most important thing that comes out of all this. The real win is that leasing standard, commodity Ku bandwidth is far, far more cost effective than the few kilohertz we have on L-band. Long-term sustainability of a free broadcast is no longer the financial burden that it once was--especially considering how much more interesting the service becomes.

There is no concrete hardware release date just yet, but on the forums Syed estimates mid-Jan. You can sign up to the Outernet mailing list on their buy-now page to be emailed when the new hardware is released. In the forums Syed also writes that the target price for the hardware is $99 US, with the intention to provide lower cost options in the future. Of course it might still be possible to DIY your own unit just like it was with the previous Outernet iterations.

We're really looking forward to this and think that this is what will finally make Outernet a very popular and useful service!

The Outernet 3.0 prototype setup
The Outernet 3.0 prototype setup

A Tutorial on Receiving HRPT Weather Satellite Images with an SDRplay RSP2

RSP2user's HRPT equipment

Over on the SDRplay forums user 'RSP2user' has put up a quality post describing how he receives HRPT weather satellite images with his SDRplay RSP2. HRPT stands for 'High Resolution Picture Transmission' and provides a much higher resolution image compared to the APT weather satellite images typically downloaded from NOAA satellites. Somewhat confusingly the picture quality of HRPT is similar to LRPT (low rate picture transmission) which is used on the Russian Meteor M series weather satellite. HRPT provides 1.1 km resolution, whilst LRPT provides 1 km resolution.

Currently there are multiple satellites broadcasting HRPT signals including NOAA 19, NOAA 18, NOAA 15, Meteor M2, Fengyun 3B, Fengyun 3C, Metop A and Metop B.

The difference in difficulty of receiving APT and LRPT versus HRPT transmissions typically occur in the L-band at about 1.7 GHz, and requires a directive high gain antenna with tracking motor to track the satellite as it passes over. This makes these images many times more difficult to receive compared to APT and LRPT which only require a fixed position antenna for reception at the more forgiving 137 MHz.

Over on his post RSP2user shows how he uses a repurposed Meade Instruments telescope tracking mount and controller to drive the tracking of a 26 element loop Yagi antenna. A 0.36dB noise figure LNA modified with bias tee input is used to boost the signal and reduce the noise figure. The signal is received by a SDRplay RSP2 and processed on a PC with USA-satcoms HRPT decoder software, which is available for purchase by directly contacting him. The HRPT signal bandwidth appears to be about 2.4 MHz so possibly an RTL-SDR could also be used, but it might be pushing it to the limit.

If you are interested, RSP2user also uploaded an APT weather satellite image reception tutorial on another post. This tutorial shows how to build a quality quadrifilar helix antenna as well.

Receiving the HRPT signal on USA-Satcoms' HRPT decoder.
Receiving the HRPT signal on USA-Satcoms' HRPT decoder.

Testing the Prototype Outernet Patch Antenna with Built in RTL-SDR

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.

Decoding the ALERT Protocol from a USGS Streamgage with an RTL-SDR

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.

3D Printing a V-Dipole Bracket

Over on his YouTube channel user Tysonpower has uploaded a video that shows how to make a V-Dipole antenna. Back in March we posted about the V-Dipole which Adam 9A4QV first described. A V-Dipole is a simple antenna that normally consists of two metal rods, a terminal block and coax cable. It is particularly effective for reception of low Earth orbit satellites like the NOAA and Meteor M2 weather image satellites with an RTL-SDR or other similar SDR.

In his video Tysonpower shows how to build a slightly more rugged version using a 3D printed part instead of a terminal block. Aluminum welding rods are used for the elements. The 3D printed part ensures that the correct 120 degree ‘V’ angle is maintained and also provides a means for mounting the antenna to a pole. The 3D printing STL files are available on Thingiverse. Note that the video is in German, but English subtitles are available.

Note that we will also have a dipole antenna capable of being used as a V-Dipole available in our store in a few weeks time.

(Almost) Receiving HRPT with the ADALM-PLUTO and a WiFi Grid Antenna

Over on YouTube user Tysonpower has uploaded a video showing how he was (almost) able to receive the HRPT signal from NOAA18 with an ADALM-PLUTO, LNA4ALL and a WiFi grid antenna.

Most readers will be familiar with the low resolution 137 MHz APT weather satellite images transmitted by the NOAA weather satellites. But NOAA 15, 18, 19 and well as Metop-A and Feng Yun satellites also transmit an HRPT (High Resolution Picture Transmission) signal up in the 1.7 GHz region. These HRPT images are much nicer to look at with a high 1.1 km resolution. If you follow @usa_satcom on Twitter you can see some HRPT images that he uploads every now and then.

However HRPT is quite difficult to receive and decode because the bandwidth is about 3 MHz so something with more bandwidth than an RTL-SDR is required. The signal also needs a ~1 meter or larger dish antenna as it is very weak, and you also need a motorized pointing system to track the satellite with the dish as it passes over.

Despite the difficulty in his video Tysonpower showed that he was able to at least receive a weak signal using a non-optimal 2.4 GHz WiFi grid dish antenna, LNA4ALL and his ADALM-PLUTO. The signal is far too weak to actually decode, but it’s still pretty surprising to receive it at all. In the future Tysonpower hopes to be able to improve his system and actually get some image decodes going. Note that the video is in German, but there are English subtitles available.