A LimeSDR Mini Based Es’Hail-2 DATV Ground Station Uplink

Daniel Estévez has posted on the LimeSDR Mini CrowdSupply blog about his ground-station build for the Es'Hail-2 satellite. Es'Hail-2 is the first geostationary satellite with amateur radio transponders on board. The LimeSDR Mini is a $159 RX/TX capable SDR with 10 MHz to 3.5 GHz frequency range.

The Es'Hail-2 satellite is positioned at 25.5°E which is over Africa. It's reception footprint covers Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia. There are two amateur transponders on the satellite. One is a narrow band linear transponder which uplinks from 2400.050 - 2400.300 MHz and downlinks from 10489.550 - 10489.800 MHz. Another is a wide band digital transponder for digital amateur TV (DATV) which uplinks from 2401.500 - 2409.500 MHz and downlinks from 10491.000 - 10499.000 MHz.

Daniel's ground station uses a LimeSDR Mini running on a Beaglebone Black. A 2.4 GHz WiFi parabolic grid antenna is used to transmit to the satellites digital amateur TV uplink. In order to generate enough power for the uplink transmission a GALI-84 amplifier chip is cascaded with a 100W power amplifier. All the electronics are enclosed in a watertight box and placed outside.

A LimeSDR Mini Based Es'Hail-2 DATV Uplink Ground Station
A LimeSDR Mini Based Es'Hail-2 DATV Uplink Ground Station
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The HAARP Project Explained Simply

Over on YouTube Curious Droid has uploaded an interesting video that attempts to explain the purpose of the HAARP transmitter project. The High Frequency Active Auroral Research Program (HAARP) is an ionospheric research program based in Alaska. It consists of a high power transmitter and antenna array which is used to excite a portion of the atmosphere in order to study the ionosphere and investigate methods of affecting radio communications. Recently HAARP was also used in an art project called "Ghosts in the Air Glow" which saw HAARP used to transmit several audio art pieces.

HAARP has also been a popular target of conspiracy theorists who believe that the transmitter must have some sort of sinister purpose. Curious Droid's video explains the purpose and science behind HAARP elegantly, hopefully dispelling any conspiracy theories.

He also explains where some of the conspiracy theories may have originated from. The original idea that HAARP was based on was a patent claiming the ability of Ionospheric heating to disrupt communications, take down missiles & satellites, affect weather, scan the earth and even affect brains. However, a project with such abilities would require ridiculous levels of electrical power and land space for the antennas, making it very unrealistic.

Why is Project HAARP so controversial?

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Reverse Engineering and Controlling a Wireless Doorbell with an RTL-SDR and Arduino

Thank you to Shreyas Ubale for submitting his blog post about reverse engineering a wireless doorbell, and then performing a replay attack. Shreyas had purchased a wireless doorbell set containing one button transmitter and two bell receivers. However, his situation required two transmitters, one for visitors at the door, and one to be used by family within his house.

In order to create a second transmitter he decided to reverse engineer the doorbells wireless signal, and use that information to create an Arduino based transmitter. His process involves first using an RTL-SDR to determine the transmission frequency, then using the rtl_433 software to capture the raw waveform which he then analyzes manually using Audacity. Once the binary string, length and pulse width is known he is able to program an Arduino connected to a 433 MHz transmitter to replicate the signal.

In future posts Shreyas hopes to explore other ways to transmit the signal, and eventually design a simple but configurable 433 MHz push button that supports RF, WiFi, and can support the IFTTT web service.

If you're interested, check out some of our previous posts that highlight many other successful reverse engineering experiments with RF devices and SDR.

Doorbell Signal Analysis in Audacity. Captured with an RTL-SDR.
Doorbell Signal Analysis in Audacity. Captured with an RTL-SDR.
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ExtIO_RTLSDR# – Modified ExtIO for SDRUno/HDSDR with Direct Sampling Mode

Fixed RTL-SDR EXTIO for SDRUno.
Fixed RTL-SDR EXTIO for SDRUno.

Over on our forums user qrp has released a modified ExtIO that allows the direct sampling mode to work correctly in SDRUno. SDRUno is SDRplay's official software for their RSP line of software defined radios, but SDRUno can also work with ExtIO input dlls which allow other SDRs like the RTL-SDR to be used.

The commonly found RTL-SDR ExtIO however doesn't seem to work properly with direct sampling mode in SDRUno, so HF on RTL-SDR Blog V3 or other direct sampling modified RTL-SDR dongles is inaccessible. The new ExtIO fixes the direct sampling problem, and also enables a Remove DC algorithm to remove that center spike, which isn't an option in SDRUno.

To use the ExtIO simply extract the ExtIO_RTLSDR_u8.dll and rtlsdr.dll files from the zip file into a folder on your PC. Then from the Start Menu find the SDRUno (EXTIO) shortcut and run it. When it asks you, select the ExtIO_RTLSDR_u8.dll file. Note that you will probably need to use the older v1.22 SDRUno version as V1.31 doesn't appear to have an ExtIO version.

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SignalsEverywhere Podcast: Satcom Piracy Interview

Corrosive from the SignalsEverywhere YouTube channel has released a new episode of his podcast. In this episode Corrosive interviews an anonymous informant who has an interesting story about his involvement with the UHF Military SATCOM pirate radio scene in Brazil. Corrosive also explains a bit further about what SATCOM is and why it's so susceptible to piracy. He also notes that piracy on Inmarsat L-band frequencies is also becoming more common.

The UHF-SATCOM band is anywhere between 243 - 270 MHz and contains fairly strong signals from many several US satellites that can be received with a simple antenna and any UHF radio/SDR. Many of the satellites are simple repeaters without security, and pirates from Mexico and South America often hijack the satellite for their own personal use. In the past, and possibly even still today hijackers involved in drug trafficking and other illegal activities made use of these insecure military satellites for long range communications. Reception of these satellites is generally available in Canada, US, Mexico, South America, Europe and Africa.

Satcom Crackdown; Satellite Piracy on After The Show Podcast

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Tracking and Recovering A NWS Weather Balloon & Radiosonde with an RTL-SDR

Over on YouTube OLHZN High Altitude Balloons has posted a very entertaining video showing how to use an RTL-SDR and small grid dish antenna to track and recover a fallen weather balloon and its radiosonde. OLHZN writes:

The US National Weather Service (#NWS) launches over 200 weather balloons everyday carrying an LMS-6 #radiosonde / rawinsonde made by Lockheed Martin to an altitude of over 100,000 ft. and you can track & follow the flights from home and even find the landing site and pick them up! This is a fun #DIY project that you can do yourself from home and I'll show you how to do it here along with some tips so you can go find yourself a weather balloon & radiosonde!

How to track & recover a NWS weather balloon & radiosonde 🎈🎈 DIY

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SignalsEverywhere: Common Modulations Tutorial Video

This week on the SignalsEverywhere YouTube channel, host Corrosive gives us a tutorial on common modulations that you'll see on your software defined radio. His tutorial covers Amplitude Modulation (AM), Frequency Modulation (FM), Single Side Band (SSB) and Conintuous Wave (CW) modulations. In the video he shows what they look like and how to select the correct mode and bandwidth settings in SDR#. Corrosive uses an Airspy in the video, but the same concepts are valid for any SDR, like the RTL-SDR.

If you're new to SDR then this is a great introductory video to watch and learn from.

AM FM SSB and CW | Common Modulation You'll See on SDR

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An RTL-SDR and Pi 3 Based Ground Station for Simulated CubeSats

CubeSats are small and light satellites that can these days be built and launched into orbit by almost anyone with a small budget of roughly $40,000. They are a great way for schools and other organizations to get into a space based technology project. A "simulated" CubeSat is one that is not designed to be really launched into space, and is made from low cost hardware. The idea is that simulated CubeSats can be used as tools to help demystify the inner workings of satellites to the public and help CubeSat builders get experience and competence before building the real thing.

A Simulated CubeSat made from a Solar Panel board, Pi Zero, UPS and Tranceiver.
A Simulated CubeSat made from a Solar Panel board, Pi Zero, UPS and Transceiver.

A team from AMSAT have been working on creating open source CubeSat simulator hardware and software. In order to demonstrate the RF capabilities of the simulator a ground station simulator is also required. Recently the team have uploaded instructions on creating a Raspberry Pi and RTL-SDR based ground station.

If you're interested in the CubeSat simulator hardware itself, there was a presentation held back in 2018 that may be of interest to you. According to the presentation somewhere between 30% - 50% of CubeSats fail as soon as they're deployed, so building competence with simulated hardware is a good goal.

2018 AMSAT William A. Tynan W3XO Memorial Space Symposium - Saturday Sessions

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