Over on his channel SignalsEverywhere, Corrosive has uploaded a video showing us how we can create a full duplex packet radio communications system using two PlutoSDRs. Full duplex is the ability to transmit and receive at the same time. A single PlutoSDR is only half-duplex/simplex because it can only either receive or transmit at any one time. The PlutoSDR is a low cost (typically $99 - $149) RX/TX capable SDR with up to 56 MHz of bandwidth and 70 MHz to 6 GHz frequency range.
On his video Corrosive explains how full duplex operation is desirable for amateur packet radio communications as it allows for faster and more continuous exchanges. Demonstrations are performed with his PlutoSDR, SoundModem, EasyTerm, and SDRAngel. Later in the video he also speculates how it might be possible to do things like IP networks via the amateur radio bands with full duplex SDRs.
Full Duplex Radio Communication with PlutoSDR Tutorial
Over on his blog, DXer OH2-2192 was frustrated by lots of local electrical noise showing up on the HF bands on his Airspy + Spyverter SDR receiver. He discovered that the majority of the noise he was seeing was coming from the switch mode power supplies that power the electronic devices used in his setup. Switch mode power supplies are very common in the modern world, with almost every electronic device using one to efficiently convert wall AC into DC power. However, they convert power by rapidly switching on and off, and these on/off square wave pulses cause a lot of RF noise especially on the HF spectrum.
Instead of changing to noise free linear regulators which are expensive, very heavy and big, OH2-2192 decided that he'd try creating a Faraday cage shield out of metal mesh to enclose all his switch-mode power supplies. Using a simple AM loop antenna and Airspy's Spectrum Spy software he measured the amount of noise produced by a switch-mode supply placed inside and outside of the cage. The results he saw were very promising with the shielded supply eliminating the noise almost entirely.
Faraday Cage Shield for Switch Mode Power Supplies (Right image shows the results of a switching supply placed outside and inside the Faraday cage)
Over on YouTube Tech Minds has posted a video explaining what Es'hail-2 satellite is and why it is interesting for hams and SDR users. Briefly Es'hail-2 is a recently launched geostationary TV satellite that covers Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia.
What's special about it is that apart from the TV transmitters, it also contains the worlds first amateur radio transponder in geostationary orbit. So amateur radio users within the region covered by the satellite can simply point their antennas to a fixed position in the sky to transmit to the satellite, and the signal will be rebroadcast over the entire covered area. With a simple LNB, satellite dish and SDR the signals can be received.
After explaining Es'hail-2 Tech Minds also shows a demo of Es'hail-2 radio traffic using a public WebSDR.
The Worlds First Geostationary Satellite For Ham Radio - Es'Hail 2 - Qatar OSCAR-100
The SDR is advertised to cover HF + 6m (50MHz) and includes two 16 bit 50 ohm input ADCs and two 14 bit outputs. Based on the Xililinx Zynq 7020 FPGA running an ARM cortex A9 processor it’s plenty powerful to handle the various modes frequently seen in the amateur bands and then some while supporting an impressive 122.88 MS/s sample rate.
The RedPitaya – 3D Rendering
This hardware is also fully compatible with the HPSDR software platform which is an open source project for amateur radio SDR operation.
While this radio is built with amateur operation in mind, it is still a very capable platform that could be used for experimentation albeit with a more restricted frequency range that what you may be used to with traditional software defined radios.
The radio retails for $499 euros and will be available for pre-order from RedPitaya until March 31st of 2019.
Over on YouTube user TheGazLab has uploaded a video that reviews the Airspy HF+, and also shows how to use the HF+ with SDR# and WSJT-X in order to create a FT8 monitor. The Airspy HF+ is high dynamic range HF/VHF receiver designed for DXing.
In the video TheGazLab demonstrates to us the decoding in real time, and explains the CAT control SDR# plugin that he's using. The CAT control plugin when combined with a virtual serial port driver allows the WSJT-X program to automatically tune SDR# to the FT8 frequency selected in WSJT-X.
Later in the video he also discusses the SpyServer network which allows SDR# users to connect to remote public Airspy and RTL-SDR units over the internet. He demonstrates connecting to a public server in the UK, and decoding FT8 via the remote server. The video also shows the new SpyServer interface by @zakhttp which nicely lays out the world SpyServer network on a map, making it easy to choose a desired location to listen to.
Airspy HFPlus, SDR# and WSJT-X with full CAT control decoding FT-8
Over on YouTube user hubmartin has uploaded a video showing how to use an RTL-SDR and the Universal Radio Hacker (URH) software to reverse engineer and clone a 433 MHz remote control. URH is used to extract the signal timing and modulation characteristics as well as the binary/hex code.
Then in order to clone the signal hubmartin uses a cheap IoT microcontroller with button and 433 MHz transmitter attachments. Some C code is then used to program the microcontroller and 433 MHz transmitter with the extracted signal information and to transmit on a press of the button. In his example hubmartin uses his cloned dongle to control a wireless power plug and a motorized projector screen.
Universal Radio Hacker SDR Tutorial on 433 MHz radio plugs
Over on YouTube Corrosive from channel SignalsEverywhere has uploaded a new video in his series on Digital Amateur Television (DATV). The new video shows us how to use a transmit capable SDR like a LimeSDR or PlutoSDR to transmit DATV with a free Windows program called DATV Express.
In the video he explains the various transmit and video encoding settings, and then demonstrates the signal being received on SDRAngel with an RTL-SDR (which he explained in his previous video)
DATV DVB-S Transmitter With a LimeSDR or Pluto SDR and DATV Express
Es'hail 2 was launched last November and it is the first geostationary satellite to contain an amateur radio transponder. The 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.
Although the satellite was launched last year, turning on the amateur transponders has been slow because the commercial systems of the satellite have higher priority for testing and commissioning. However, within the last day the Es'hail 2 team have now begin testing the amateur transponder, and the test signal has been successfully received by several enthusiasts (just check out the Twitter feed). There also appears to have already been a suspected pirate CW signal broadcasting "WELCOME DE ES2HAIL". Actual uplink use of the satellite is not currently wanted, and from the Amsat forums one of the engineers writes:
Before the IOT starts there will be a TRR (test readyness review) in front of the customer. All the testplans and test-specifications will be reviewed. When the test is done there will be a TRB (test readyness board). In the TRB they have to show/present all the measurement results (e.g. inband performance like Gainflatness, Groupdelay... aso.) and compare these results with the specification in the contract. Each unwanted signal makes the measurement difficult and needs to be explained or leads to a so named NCR (non conformance report).
The IOT will be done in shifts/nightshifts and with unwanted signals (if not explain able) some measurements needs to start again and again and leads in addition to a delay for the handover and operation of the satellite.
Maybe that helps to understand why it is really important to have only the IOT uplink signal.
To measure the pattern of each antenna the satellite will be moved east/west by the propulsion system of the DS2000 Bus and the signal level is measured by the IOT station on ground (some cuts) .
The commercial beacon can maybe be switched from LEOP Omni antenna to on station antenna when the satellite is placed in the final slot. This should be the reason for the change of the commercial Ku Band beacon signal level the last days.
If you are interested in receiving Es'hail 2, but live outside the footprint, or don't have a receiver then you can use Zoltan's OpenwebRX live stream of the narrow band portion of the Es'hail 2 downlink. At the moment the beacon doesn't appear to be transmitting, but we expect it to be on and off during the next few days. In his set up he uses an RTL-SDR V3, Inverto LNB, 90cm dish, a DIY bias tee and a Raspberry Pi 3.
He also took a recording of the pirates CW transmission shown in the video below.
