Using Two PlutoSDR’s for Full Duplex Packet Radio Communications

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

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YouTube Tutorial: Decoding POCSAG and FLEX Pager Messages on Windows with PDW

Pager systems are famously known to be insecure, and due to the lack of encryption and high transmit power anyone with an RTL-SDR or other SDR can receive and decode pager messages. The users of pagers are mostly hospitals and doctors, and IT infrastructure professionals who need to be notified of server warnings and errors quickly. We have a text tutorial on decoding these messages with an RTL-SDR available here, and there are several previous posts discussing how insecure they are. 

If you prefer a video tutorial, M6LME on YouTube has recently uploaded one where he explains the PDW pager decoding software, the VB-Audio 'banana' audio mixing software, and how to use SDR-Console with an RTL-SDR and the aforementioned software to receive and decode the signal.

How to Decode POCSAG & FLEX using an RTL-SDR Dongle

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Reducing HF Electrical Noise by Using a Faraday Cage for Switch-Mode Power Supplies

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
Faraday Cage Shield for Switch Mode Power Supplies (Right image shows the results of a switching supply placed outside and inside the Faraday cage)
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Amateur Radio on the Es’hail-2 Satellite Explained on YouTube

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

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SignalsEverywhere Podcast EP1: Es’hail-2, Favorite RTL-SDR Blog Posts and What SDR Should I Get?

Corrosive from the SignalsEverywhere YouTube channel is starting up a radio/SDR related podcast, and today has released episode one. The podcast is 22 minutes long, and in that time he discusses Es-hail-2, a geosynchronous satellite with an amateur radio transponder that was recently launched and activated, some of his favorite recent posts from our blog here at RTL-SDR.com, including posts about a 3D printed V-Dipole holder, Radwave RF Analyzer, cloning 433 MHz devices, and finally he ends the podcast by discussing the question of what SDR is right for you.

Podcasts are a great way to catch up on what's happening in the SDR and radio world so check it out below or over on the SignalsEverywhere podcast post.

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rsp_tcp: An rtl_tcp compatible IQ Server for SDRplay SDRs

The SDRplay team have released an updated version of a program called "rsp_tcp" (originally written by F4FHH Nicholas). This is a streaming IQ server for SDRplay devices, which is directly ported from the original rtl_tcp code that was designed for RTL-SDRs. The rsp_tcp code is fully compatible with the rtl_tcp protocol, so this should allow almost any software that accepts an rtl_tcp stream as an input to use an SDRplay device as the SDR hardware instead of an RTL-SDR.

The downside to using this server is that in order to be compatible with the standard rtl_tcp protocol, the software will downgrade the RSP data stream from 14-bits to 8-bits only, thus forfeiting the RSP's greater dynamic range. However, if a custom ExtIO plugin is used on the client software, then the full 14-bits can be restored.

On their forums the SDRplay team write:

This software is based on a fork of F4FHH’s version of RTL TCP Server. It has been updated to support the RSP features, but also contains an extended mode. The extended mode allows the client (via a compatible interface) to fully control all aspects of the RSPs, including notch filters, Bias-T enable and switching ports (where applicable)

The user guide for the server software can be found on our downloads page and also here: https://www.sdrplay.com/docs/SDRplay_RS ... _Guide.pdf

We have provided binaries for Windows, Mac and RPi on our downloads page and the source code for all platforms can be found on our GitHub repository: https://github.com/SDRplay/RSPTCPServer

To utilise the extended mode, extra commands need to be sent from the client. We have provided an example of this in the form of an ExtIO plugin. You can find the Windows dll on our downloads page and the source code for the plugin on our GitHub repository: https://github.com/SDRplay/ExtIO_RSP_TCP

In standard mode, the server will be compatible with any RTL server client.

The team also note that they have updated their Raspberry Pi SD card to include the server.

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Android App: Phonetic Alphabet Trainer

Thank you to Manuel DO5TY who wrote in and wanted to share his Android App that helps you to memorize the ham radio phonetic alphabet. The phonetic alphabet is a way to avoid confusion when speaking out similar sounding English letters such as "p" and "b". Instead of "pea" and "bee" these are spoken as "papa" and "bravo". The phonetic alphabet is commonly used in all sorts of radio communications, so it is a good skill to learn for potential hams, radio operators or even for people just listening in to radio communications.

The Phonetic Alphabet Trainer is an App you can easily learn the Alphabet that is used in the Military and on Hamradio contacts. The App has different options for you to learn and memorize the Alphabet. Your current Skill Level is displayed on the main screen and indicates how good you are at the Phonetic Alphabet.

Alphabetlist
Take a look at the Phonetic Alphabet and see what words are used for each Character.
You can also hear how the words are spoken out with a simple button click.

Train with random Strings
Let the App generate random Strings and translate them into the Phonetic Alphabet.
With that you can memorize the Alphabet and learn how to write them correctly at the same time. The String gets one Character longer each time you got Five in a row correct.

Train with Hamradio
The App generates a random Callsign and speaks it out loud in the Phonetic Alphabet. Your Task is it to Write down the correct Callsign. You only have one try to get it right, your score is how many you recognize correctly in a row.

Phonetic Alphabet Trainer - App Promo

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RedPitaya Announces Pre-order for STEMLab HF SDR Transceiver

RedPitaya has just announced their next SDR platform, the STEMlab 122.88-16 which is a software defined radio intended to be used as an HF transceiver on the amateur radio bands.

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.

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