Category: HF

Building an OpenWebRX Server with an RTL-SDR Blog V3 for HF Monitoring

Thank you to Ramadhan (YD1RUH) who has put together a brief set of commands showing how to quickly get setup with OpenWebRX and an RTL-SDR Blog V3. OpenWebRX is a web based SDR program that allows users to use their SDR over a network or internet connector. It is compatible with several SDRs including the RTL-SDR.

 The installation is based on Ubuntu, and uses docker for the install. He also shows how to set up the OpenWebRX configuration file so that it will use the Q-branch direct sampling mode in RTL-SDR Blog V3 dongles for HF reception.

A demonstration of the result can be seen on Ramadhan's public OpenWebRX page. You can select between the various enabled HF bands in the lower left.

OpenWebRX HF reception running on an RTL-SDR Blog V3 dongle.

A GNU Radio DCF77 Time Signal Decoder

DCF77 is a long wave time keeping signal transmitting at 77.5 kHz from Frankfurt, Germany. It has been active since 1 January 1959. Using simple amplitude modulation, the signal encodes the current time and date, which is used by some devices like railway station clocks in Germany. Because it's a long wave signal transmitting at 50kW, it's possible to receive the signal across Europe, and sometimes even further away if propagation conditions are good.

Recently a DCF77 receiver and decoder program based on Python and GNU Radio has been uploaded to GitHub by henningM1r. It includes a simulator written in Python so you can simulate your own DCF77 signal for testing the receiver too.

Currently the decoder has been tested to work with an Airspy HF+ Discovery SDR, but it should work with any SDR capable of receiver 77.5 kHz if the GNU Radio source block is changed out.

DCF77 GNU Radio Decoder

Maverick-603 Project Suspended Indefinitely

Back in December 2022 we posted about the Maverick-603 which was at that stage Crowd Funding on Crowd Supply.

It was to be a US$149 FT8 receiver based on an open source RF chip design, capable of acquiring signals between 7 MHz and 70 MHz (technically 1 MHz to 100 MHz). Shipments were expected to begin in April 2023.

Unfortunately the Maverick team just released today that the project will be suspended indefinitely due to logistical issues. Backers of the project will receive a full refund.

The Maverick-603 project has been indefinitely suspended due to unforeseen logistical obstacles. No funds have yet been spent and all backers will receive full refunds. If you backed this project, your refund will be issued within the next week to the credit card you originally used. If your credit card is no longer valid, please contact Crowd Supply support before midnight UTC on Friday, April 28, 2023 to arrange your refund. If the Maverick-603 project is revived, we will post another update. Thank you for your support and patience.

The Maverick-603 FT8 Receiver
The Maverick-603 FT8 Receiver

The SDRSharp ListenInfo Plugin

SDR# is a popular software defined radio program that is compatible with RTL-SDR, Airspy and several other SDR devices. One feature is the ability for third parties to develop plugins for the software.

One recently released plugin that is gaining popularity is the "ListenInfo" plugin. The ListenInfo plugin uses a publicly available database of shortwave stations to display frequency station info for the LW, MW, SW bands within the SDR# spectrum display.

If you've ever been browsing the shortwave bands and wondered where a station is broadcasting from, and what it's transit power, beam direction and transmit schedule are like, then this will be a very useful plugin for you.

SDR# ListenInfo Plugin
SDR# ListenInfo Plugin

Upgrading the Mahahit DSP1 and Malahit Chinese Clones into the Mahahit DSP2

Mahiteam is a Russian company that produces the relatively popular Malahit DSP1/DSP2 and Malahit DDC portable SDR radio which are great for shortwave listening, but can also cover up to 2 GHz. Manuel L. has been following developments and notes that Malahiteam are offering the ability to upgrade their DSP1 (and any DSP1 Chinese clone) into Malahit 2 units by sending the device in for a chip replacement. Manuel writes:

Hi. Recently it is possible to upgrade the Malahit DSP1 (original) and also the China clones (if registered in Russia) of the Malahit with a new CPU and if necessary a new audio codec chip. This upgrade has been officially released by the Malahiteam the developers.

This allows custom DSP2 firmware to run on the DSP1 and clones. This makes the device more powerful and also has the option of installing a Bluetooth board and controlling it via the software, as is the case with the DSP2.

This upgrade can be carried out directly in Russia by the Malahit team.

For Europe this is done by Jochen Köster DC9DD (Malahit Servise Europa) who converted the first DSP1 and China clones outside of Russia.

In the US, the future KD9NXV makes Mark Roy (USA Service Malahit).

I have tested the first conversions outside of Russia and it is a very big upgrade of the devices. They work a lot better now. I have shown this in several YouTube films. More information and contacts to the service teams outside of Russia can be found at Telegram and the Malahit Facebook group

https://t.me/+BOQmKPgV4lM2NDZi

https://www.facebook.com/groups/malahitsdrinternational/

YouTube Video Upgrade Malahit DSP1 and China Clone:
https://youtu.be/h9zepfkyK3Q
https://youtu.be/-v5Iuv7pmHU
https://youtu.be/6Z-hecUeMG0
https://youtu.be/iBWN2HHLQ94

The Malahit DSP2
The Malahit DSP2

Maverick-603: An Affordable FT8 Receiver with an Open Source RF Chip

The Maverick-603 is a US$149 FT8 receiver based on an open source RF chip design which is capable of acquiring signals between 7 MHz and 70 MHz (technically 1 MHz to 100 MHz). It is currently undergoing Crowd Funding on Crowd Supply with 7 days left in the campaign. Shipping is expected to begin in April 2023.

FT8 is a popular weak signal propagation digital mode used by ham radio enthusiasts. FT8 signals can be received and decoded all over the world even with low transmit power and poor propagation conditions thanks to its highly error tolerant encoding. A dedicated FT8 receiver allows enthusiasts to set up a 24/7 FT8 monitor without dedicating more expensive ham radio equipment to the task. Note that a computing device like a PC or possibly a Raspberry Pi 4 will still be required to run the FT8 decoding software as this is a software defined radio.

The Maverick-603 is based on a custom open source RF chip design made possible by the company eFabless. It is now possible to cheaply design and produce custom ASIC chips (at least at the lower end of the technology scale), replacing more costly FPGA designs. The technical specs of the Maverick-603 are:

  • MCU: ATMEGA1608
  • Power Supply: 3.3 V / 10 mA
  • Operating Frequency Range: 1 to 100 MHz
  • Minimum Signal Strength: -25 dBm
  • Input Antenna Impedance: 50 Ohm
  • Data Interface: SPI
  • Board Size: 2" x 1.75"
  • Capable of receiving FT8 signals
  • 7 - 70 MHZ frequency range
  • Low-power operation (1.8 Volts) means no battery or outlet is required
  • USB Connection
  • A compact surface area
The Maverick-603 FT8 Receiver
The Maverick-603 FT8 Receiver

A Broad Overview About HF on the RTL-SDR Blog V3

Over on YouTube, Tom the Dilettante has uploaded a video demonstrating how to receive HF signals with an RTL-SDR Blog V3 running in direct sampling mode. This is something already known to most RTL-SDR fans, but on the RTL-SDR V3 we have built in a direct sampling circuit that enables reception below 24 MHz with a simple settings change in software.

In the past and with other dongle brands, enabling direct sampling required hardware mods involving directly soldering a wire antenna to very small pins or pads. Direct sampling is not a high performance mode for HF, but in many situations it can be good enough for casual listening. 

In his video Tom demonstrates HF reception with the RTL-SDR Blog V3 and an MLA-30 active loop antenna. This is a cheap loop antenna available on Aliexpress that works very well for the price.

Listen Around the World - No Internet Required (HF & Shortwave on RTL SDR)

Video on Receiving HF Signals with the RTL-SDR Blog V3

Over on YouTube TheSmokinApe has uploaded a video showing how to use the direct sampling mode on RTL-SDR Blog V3 devices to receive HF transmissions, such as the ham bands, short wave and AM broadcast. In the video he shows how to activate direct sampling mode in SDR#, and then goes on to show reception of a few HF signals.

We note that an appropriate HF capable antenna is required to receive HF signals. The multipurpose dipole kits we sell are for VHF/UHF reception only. A simple and low cost HF antenna could just be a long wire running through your house.

HF Ham Radio with RTL-SDR Made EASY!