Category: Amateur Radio

Homebrew SDR Transceiver for HF Operation

Traditionally when we think about Software-Defined Radio we’re thinking about little USB adapters that unlock a world of radio in the palm of our hands. This is done by allowing us to directly sample the IQ data from the mixer within the SDR.

However, this isn’t the only way to experience Software-Defined Radio. Ham Radio operator [Charlie Morris] has uploaded a 10 part series on YouTube explaining how he implemented his own HF transceiver, including custom software. Some of the components such as the amplifier and filters are built completely from scratch, other components use a little DSP magic from a “Teensy” microcontroller. 

Charlie actually samples the I and Q data in a similar way that today’s SDRs do and even implemented the transmit side of the radio so he can make contact with other radio operators around the world, and man… it sounds good!

You can find a complete playlist from Charlie with well-explained videos that go over his entire process from planning, schematics, layout and final operation. The channel appears to be quite active and will surely continue to pump out amazing content.

Homebrew SDR SSB Rig – Part 9 First On-Air QSO!

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

Decoding FT8 with an RTL-SDR Blog V3 in Direct Sampling Mode

Over on YouTube user ModernHam has uploaded a useful tutorial showing how to use our RTL-SDR Blog V3 dongles for FT8 monitoring. The RTL-SDR Blog V3 has a built in direct sampling circuit which allows for reception of HF signals without the need for any upconverter. FT8 is an amateur radio weak signal digital communications mode which can be received all around the world even with low transmit power.

In his setup he uses SDR# and Virtual Audio Cable to pipe audio to the WSJT-X decoder. His video goes through all the steps and settings that need to be set and then shows a demo of some signals being received. ModernHam also has another video uploaded a few days earlier which is a more general introduction to FT8 decoding.

If you're interested we uploaded a tutorial last year that shows how to set up a Raspberry Pi 3 based FT8 decoding station with a V3 dongle.

Decoding FT8 with a RTL-SDR (Software defined Radio)

Hermes-Lite: A Low Cost Amateur Radio SDR Made from A Repurposed Cable Modem Chip

The HPSDR Hermes SDR is an open source amateur radio SDR transceiver project that was released as far back as 2011. More recently Steve Haynal has been working on a Hermes-Lite project which is intended to be an opensource open hardware low cost amateur radio HF transceiver which is based on the HPSDR Hermes SDR project software and FPGA DSP implementation.

The Hermes-Lite is able to be very low cost (less than $300) because it is based on the AD9866 chip which is a mass produced RF front end (LNA + ADC & DAC) used in cable modems. Because it is a mass produced commodity, the chip only costs approx. US$35-$25 on Mouser depending on quantity. The chip has a 12-bit 80 MHz ADC and DAC, meaning that if used without any analog mixer front end (like in the Hermes-Lite) it can receive the entire spectrum between 0.1 to 38 MHz all at once.  

The Hermes-Lite is also a lot more than just the RF chip, as it contains a set of switched RF filters and a 5W power amplifier for TX. It also interfaces with a PC via Ethernet and has a built in FPGA for DSP processing.

Recently Steve presented at the FOSSi Foundation Latch-Up conference on May 4-5, and a YouTube recording of his presentation is shown below.

[First seen on The SWLing Post]

Hermes-Lite: Amateur Radio SDR

Decoding Es’Hail-2 DVB-S2 Realtime in Linux with LeanDVB

Last week we posted about M Khanfar's YouTube video that showed how to decode Es'Hail-2/QO-100 DVB-S2 on Ubuntu with the LeanDVB decoder. However, the method he showed was not in real time as it involved recording an IQ file in GQRX first, then decoding that IQ file. Similarly we also posted last week about a Windows based real time decoder.

M Khanfar recently wrote in again and wanted to show that real time decoding is possible with LeanDVB. The method is to simply pipe the output of the rtl_sdr command line decoder in LeanDVB, and then into VLC. He notes that his PC isn't actually fast enough to decode in real time without lag, but a modern i5 CPU would work well. The actual terminal command is shown in his YouTube video description.

This is Realtime live DVB-S2 Decoding done , without need to record .RAW file , its live and easy method by one click ! In this video i decoding 2MS symbol rate from wideband transponder of QO-100 beacon , you can decoding 1MS , 0.5MS , 333KS , 125KS symbol rate ! The lower Symbol, the faster speed for decoding! , the Amateurs operators on QO-100 Uplink DATV DVB-S2 at 0.5 , 333 , 125Ks , so its easy to Live Decoding Now ! With very low SNR ! , so the normal SDR can coverage wideband beacon of 2Ms symbol and all Ham uplink ! , if you have an SDR that can coverage 27.5 mb of bandwidth, so you can easy decoding Live a standard commercial satellite channels! But it need a high speed Pc .

QO-100 Realtime Live DVB-S2 Decoding

RSGB Talk – The Farnham WebSDR: DC to Microwaves on your Smartphone

Over on YouTube the Radio Society of Great Britain (RSGB) has uploaded a talk by Noel Matthews (G8GTZ) titled "The Farnham WebSDR: DC to Microwaves on your smartphone". The Farnham WebSDR runs 8 (soon to be 10) RTL-SDR dongles in order to cover multiple bands from DC to 2 GHz.

If you're interested in their talks, the RSGB also recently uploaded several other amateur radio related talks from their 2018 convention to their YouTube channel.

This presentation gives an overview of the Farnham WebSDR (http://farnham-sdr.com/) which currently covers the LF bands through to 10GHz. The presentation describes the system architecture and antennas currently used on each band and how the team has used RTL dongle receivers, available for under £10, to give good RF performance on all bands from DC to 10GHz. There is a demonstration of the SDR in use on both PC and smartphone.

RSGB 2018 Convention lecture - The Farnham WebSDR: DC to Microwaves on your smartphone

LimeSDR Angle of Arrival Experiments at 145 MHz

Two J-Poles used in LimeSDR Angle of Arrival Experiments.
Two J-Poles used in LimeSDR Angle of Arrival Experiments.

Together with some Spanish amateur radio operators, Daniel Estevez performed an experiment with the goal of detecting the angle of arrival of meteor reflections coming from the GRAVES radar at 143.05 MHz.

The GRAVES radar at 143.05 MHz is often used by amateur radio astronomers as a way to detect the echos of meteors entering the atmosphere. The basic idea is that meteors leave behind a trail of ionized air which is reflective to RF energy. This RF reflective air can reflect the signal from the powerful GRAVES space radar in France, allowing the radar signal to be briefly received from far away. Detecting the angle of arrival from these reflections could help determine where the meteor entered the atmosphere.

Their experiments used a pair of J-Pole antennas and a LimeSDR receiver. The LimeSDR has two channels and can receive the signal coherently from both channels. The phase difference in the received signals from the two antennas can then be measured, and the angle of arrival calculated.

In their testing the first tested with 145 MHz amateur radio satellites. Unfortunately due to the low elevation of the antennas and multipath from terrain obstructions an angle could not be calculated. In a second experiment they tried receiving terrestrial APRS signals. With APRS they were successful and were able to determine the angle of arrival from multiple stations. Unfortunately for GRAVES meteor echoes they were not entirely successful, citing multipath issues due to houses, and the need for a clear view of the horizon.

We note that it may be possible to perform similar experiments with our KerberosSDR coherent RTL-SDR unit.

Elektor SDR Hands-on Book + Arduino Shield HF SDR

Elektor is a popular electronics magazine and hobbyist kit store. Recently they have published a book titled "SDR Hands-on Book" written by Burkhard Kainka. The book is intended as a companion to their Arduino SDR shield kit, which is a low cost module that allows you to turn an Arduino into a 150 kHz to 30 MHz capable SDR. It is based on the G8JCFSDR, which is an RF front end downconverter that allows a PC soundcard to be used as an SDR analog to digital converter.

Kainka's book goes over introductory topics such as shortwave reception, explains signal to noise ratio and interference, different types of antennas, software, digital modes, SDR measurements, receiving and finally WSPR and QRP transmission. If you're interested Jan Buiting also recently reviewed the book on the Elektor website.

Elektor are currently running a promotion and are selling the book + Arduino shield for a reduced price of €49.90.

The Elektor Arduino Shield HF SDR Kit.
The Elektor Arduino Shield HF SDR Kit.