Tagged: rtl2832u

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.

Running the PiAware ADS-B Decoder on a $9 C.H.I.P Computer

Over on his blog Adam Melton has created a post that fully details how to install FlightAware’s PiAware ADS-B feeder software on a $9 C.H.I.P single board PC. The C.H.I.P is a very small board with WiFi built in, so this makes an excellent small form factor platform for an RTL-SDR running a dedicated ADS-B decoder like PiAware.

In the post he shows how to make a cheap quarter wave ground plane antenna for ADS-B and then goes on to show the installation steps required to get PiAware running on the C.H.I.P. He also mentions his Power over Ethernet (PoE) setup which allows him to power the RTL-SDR and C.H.I.P via an Ethernet cable which also provides the network connection. A power setup like this is great for getting your receiver in a remote location without coax cable losses, although you do need to watch the voltage drop on the Ethernet cable.

The C.H.I.P is a cheap $9 single board computer that had a successful Kickstarter back in 2015. Unfortunately since the Kickstarter it has been almost impossible to obtain a unit (we’ve been waiting over a year). Hopefully more will ship soon.

PiAware ADS-B RTL-SDR Setup Test on a C.H.I.P
PiAware ADS-B RTL-SDR Setup Test on a C.H.I.P

Modded SUP-2400 Downconverters now Available at RXTXDX.com for $25

Last week we posted about KD0CQ’s interest check on his ready to go modded SUP-2400 downconverter. Interest was strong so the unit is now available for sale on a store he’s just set up at RXTXDX.com. The ready to go unit costs $25 USD including a 9V battery plug and F->SMA or MCX adapter.

Last year KD0CQ discovered that the SUP-2400 is a cheap $5 – $10 DirecTV (US satellite TV) module which can be hand modded into a downconverter for the RTL-SDR. A downconverter allows you to listen to frequencies above the maximum frequency range of the RTL-SDR by converting frequencies down into a range receivable by the RTL-SDR (or of course any other SDR). The modified SUP-2400 allows to you listen up to just over 4 GHz.

The SUP-2400 modification is moderately involved and requires soldering and desoldering SMD pieces, so this product is great for anyone who just wants a cheap and low cost downconverter which is ready to go. And at $25 USD it’s still very good value. Shipping within the USA is $7.75, and internationally it is about $13.50.

The modified SUP-2400 Downconverter
The modified SUP-2400 Downconverter

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.

Viewing Lightning RF Bursts with an RTL-SDR

Lightning produces fairly wideband bursts of RF energy, especially down in the VLF to HF frequencies. Detecting these bursts with custom radio hardware is how lightning detection websites such as blitzortung.org work.

It is also possible to detect lightning using an RTL-SDR that can tune to to HF and lower, such as the RTL-SDR V3, or an RTL-SDR with an upconverter. Over on his blog Kenn Ranous (KA0SBL) has uploaded a short post showing what lightning bursts look like on an RTL-SDR waterfall. He uses an RTL-SDR V3 to tune down to the LF – MW frequency bands and looks for wideband pulses of noise which indicate lightning.

It would be interesting to see if this type of detection could be automated with DSP so that a similar service to Blitzortung.org could be created.

Lightning Pulses
Lightning Pulses

Fixing USB Reset Problems for 24/7 rtl_433 Monitoring

Rtl_433 is an RTL-SDR compatible command line based tool for monitoring various 433 MHz ISM band devices, such as temperature sensors, weather monitors, TPMS, energy meters etc. A full list of support devices can be found on the rtl_433 Github.

Over on his blog “raspberrypiandstuff” mentions that he’s been using rtl_433 and an RTL-SDR on a remote headless Raspberry Pi to receive and monitor temperature and humidity from his weather station. From the data he’s able to produce some nice graphs that show changes over time.

However, one problem that he ran into was that the USB controller on the Raspberry Pi would sometimes hang. The only solution he’d previously found to fixing it was to physically disconnect and then reconnect the RTL-SDR. But now “raspberrypiandstuff” writes that he’s found a new solution which is to use a small C-program called usbreset.c. Combined with a bash script that detects which device the RTL-SDR is on the bus, this tool helps to automatically reset the USB on the Pi if it fails to keep the RTL-SDR logging 24/7 without physical intervention.

This may be a solution to look into if you’re experiencing similar issues with 24/7 monitoring on the Raspberry Pi. If you’re also interesting in rtl_433 monitoring, “raspberrypiandstuff” also has a post on creating a simple GUI for rtl_433.

Interest Check: KD0CQ Pre-Modified SUP-2400 Downconverters

Over on his blog KD0CQ has posted an interest check. He’d like to know if anyone would be interested in purchasing pre-modified SUP-2400 downconverters from him. We’ve posted about the SUP-2400 a few times in the past. Basically the SUP-2400 is a cheap (about $5 – $10 USD) DirecTV device which can be modified and turned into a downconverter for your RTL-SDR. A downconverter allows you to listen to higher frequencies, up to 4.5 GHz in the case of the SUP-2400 and an RTL-SDR. 

The modification involves some decent soldering skills as it involves removing some small SMD components and using wires to bridge some points. KD0CQ writes that he’s thinking of selling premodified SUP-2400 units for $20 – $25 to interested customers. If you think that you’d be interested in this please comment on his post.

SUP-2400 Circuit.
SUP-2400 Circuit.

QuestaSDR (Formerly UnoSDR) Updated: Now Supports Airspy and many new Features

Back in March Vi Vitaliy wrote in to let us know about an RTL-SDR compatible SDR program called UnoSDR that he had been working on. Vi now writes that the software has been updated, and the name has been changed to QuestaSDR to avoid confusion with SDRUno – SDRplays official software package. Vi writes:

In new version I added support AirSpy r2, AirSpy mini, Perfomance Window, Record AF, record and play iq raw data, frequency bookmarks, waterfall color scheme, change fft size, fps … calibrate options, support if converter.

The software is still in beta, and Vi would be interested in hearing any feedback or bug reports if you have any.

QuestaSDR can be downloaded from sdr-labs.com.

QuestaSDR (Formerly known as UnoSDR)
QuestaSDR (Formerly known as UnoSDR)