Tagged: l-band

Potentially Receiving up to 10 GHz with an RTL-SDR and Multiple SUP-24000 Downconverters

Back in 2016 KD0CQ discovered that a $5 DirectTV device with model name SUP-2400 could be used as a downconverter with an RTL-SDR for receiving frequencies of up to 4.5 GHz. A downconverter is a device that converts high frequencies such as 4.5 GHz down into a frequency actually receivable by the RTL-SDR. The SUP-2400 is able to be modified into a useful downconverter by opening it up and manually removing some mixing harmonic filters.

In his latest post KD0CQ shows how you could combine four modified SUP-2400 downconverters to create a quarduple conversion mixer which allows you to receive up to 10 GHz. The post goes into the mixing math and practicalities of this idea. KD0CQ writes that some amplification will most likely be required to push the signal through, and in the past he’s managed to receive up to 7.5 GHz.

The SUP-2400 Directv upconverter that can be converted into a downconverter.
The SUP-2400 DirecTV device that can be converted into a downconverter.

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

Testing the Outernet Dreamcatcher: Linux Based ARM PC with Built in RTL-SDR

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.

Continue reading

Potentially Receiving up to 10 GHz with an RTL-SDR and Multiple SUP-24000 Downconverters

Back in 2016 KD0CQ discovered that a $5 DirectTV device with model name SUP-2400 could be used as a downconverter with an RTL-SDR for receiving frequencies of up to 4.5 GHz. A downconverter is a device that converts high frequencies such as 4.5 GHz down into a frequency actually receivable by the RTL-SDR. The SUP-2400 is able to be modified into a useful downconverter by opening it up and manually removing some mixing harmonic filters.

In his latest post KD0CQ shows how you could combine four modified SUP-2400 downconverters to create a quarduple conversion mixer which allows you to receive up to 10 GHz. The post goes into the mixing math and practicalities of this idea. KD0CQ writes that some amplification will most likely be required to push the signal through, and in the past he’s managed to receive up to 7.5 GHz.

The SUP-2400 Directv upconverter that can be converted into a downconverter.
The SUP-2400 DirecTV device that can be converted into a downconverter.

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

Testing the Outernet Dreamcatcher: Linux Based ARM PC with Built in RTL-SDR

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.

Continue reading

The Outernet Dreamcatcher: A Linux Based ARM PC with Built in RTL-SDR

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 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 (Front)
Outernet active ceramic patch antenna (Rear)
Outernet active ceramic patch antenna (Rear)

Outernet Patch Antenna Pan-Tilt Servo

Over on YouTube user Tomi Simola has uploaded a video showing his servo based Outernet satellite antenna tracker. Outernet uses L-band geostationary satellites which means that they are at a fixed position in the sky. Optimal reception of the Outernet and other L-Band satellite signals can be obtained by pointing the patch antenna towards the satellite.

Tomi wanted an easy way to remotely switch the antenna to point at one of two geostationary satellites, Alphasat at 25E which has the Outernet signal and Inmarsat at 64E which has more services like AERO and STD-C. Another potential use of his tracker might be for tracking L-Band satellite while in a moving vehicle such as a car or boat. 

To automatically point the Outernet L-band patch antenna Tomi used a commonly found Pan-Tilt servo mounted inside an waterproof enclosure. On the servo is a 3D printed mount which the patch antenna is attached on. An Arduino Nano with Bluetooth module allows control of the servo.

The video below shows a test of the system, over on Reddit he has written a comment explaining the project and over on Imgur he’s uploaded some photos of the construction.

Building a Wideband Vivaldi Antenna for SDR Use

Vivaldi’s are linearly polarized broadband antennas that have a directional radiation pattern at higher frequencies. The high end SDR manufacturer RF Space produces their own Vivaldi antennas made from PCB boards which they sell online. The larger the antenna, the lower its receiving frequency, and ones that go down to about 200 MHz are almost the size of a full adult person. But all sizes receive up to 6 GHz maximum. Typically smaller versions of Vivald antennas have been used in the past for L-Band satellite reception.

Over on his blog KD0CQ noted that he always had trouble trying to purchase a Vivaldi from RF Space because they were too popular and always out of stock. So he decided to try and build his own out of PCB boards. On this page he’s collected a bunch of Vivaldi cutout or transfer images. On his second page he shows a Vivaldi antenna that he built out of PCB material, just by using scissors and semi-rigid coax. With the Vivaldi placed outdoors he’s been able to successfully receive and decode L-Band AERO on his Airspy Mini even without an LNA. 

KD0CQ writes that he’ll update his blog soon with more results.

Simple Vivaldi antenna by KD0CQ cut out of PCB board.
Simple Vivaldi antenna by KD0CQ cut out of PCB board.

30% Off Outernet L-Band RTL-SDR DIY Kits – $70 for RTL-SDR, LNA, Antenna, CHIP and Battery

Outernet is an L-band satellite service that aims to be a “library in the sky”. They are constantly transmitting data such as up to date news, weather updates, Wikipedia pages, books, ISS APRS repeats and much more. Their DIY receiver kit consists of a lithium battery pack, L-band patch satellite antenna, LNA with built in filter, C.H.I.P mini Linux computer and an RTL-SDR E4000 or V3.

The DIY kit is normally priced at $99 USD, but right now they are running a 30% off Christmas promotion, bringing the price down to $69.30 USD. If you don’t need the battery pack, the sale price is then only $55.30 USD. This seems like a very good deal as normally just the patch antenna and Outernet LNA would be almost $50 USD in total.

To get the discount you must purchase directly from their store and use the coupon 30OFF. The promotion ends 31 December 2016 at 11:59 PM CST so get in quick.

The Outernet items you get for $70 USD.
The Outernet items you get for $70 USD.