Tagged: satellite

Receiving the Bitcoin Blockchain from Satellites with an RTL-SDR

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 https://blockstream.com/satellite/howitworks/)
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.

Listening to Astronauts on the ISS with an RTL-SDR and V-Dipole (ARISS Contact with Astronaut Paolo Nespoli)

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.

Demodulating the Outernet signal with leandvb and an RTL-SDR

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.

Patch vs Dish Antenna for Outernet
Patch vs Dish Antenna for Outernet

Outernet: Patch antenna now sold seperately + other products

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.

Current Outernet Products
Current Outernet Products

Using a TV Dipole Antenna for NOAA Satellite Reception

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.

Skylark Image for Outernet’s Dreamcatcher RTL-SDR

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.

Receiving the Bitcoin Blockchain from Satellites with an RTL-SDR

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 https://blockstream.com/satellite/howitworks/)
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.

Listening to Astronauts on the ISS with an RTL-SDR and V-Dipole (ARISS Contact with Astronaut Paolo Nespoli)

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.

Demodulating the Outernet signal with leandvb and an RTL-SDR

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.

Patch vs Dish Antenna for Outernet
Patch vs Dish Antenna for Outernet

Outernet: Patch antenna now sold seperately + other products

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.

Current Outernet Products
Current Outernet Products

Using a TV Dipole Antenna for NOAA Satellite Reception

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.

Skylark Image for Outernet’s Dreamcatcher RTL-SDR

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.

SatNOGs No-Rotator Setup

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.

We’ve also recently seen similar no-rotator builds discussed over on their forums and on Twitter.

SatNOGS turnstile no-rotator implementation
SatNOGS turnstile no-rotator implementation

Receiving NOAA 19 HRPT with a HackRF, LNA4All and Cooking Pot Antenna

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.