Category: Amateur Radio

SARCTRAC Mk3b: A $290 Satellite Antenna Rotator

In January we posted about the AntRunner, which is a $325 (incl. shipping) satellite antenna rotator shipped from China. Recently we've come across another low cost satellite rotator from Australia called the "SARCTRAC Mk3b" which was developed as part of a school amateur radio educational program. This rotator fully assembled comes in at AU$400 + AU$50 worldwide shipping (US$290 + US$40 = US$330), making it's price comparable with the AntRunner. SARCTRAC can be purchased from the sarcnet products page. Currently only the fully built unit is available, but in the future they plan to offer a cheaper kit option.

We're yet to test the SARCTRAC Mk3b, but based on an overall review of it's advertising, it appears that the SARCTRAC has some superior specifications and a superior design when compared to the AntRunner.

Unlike the AntRunner, SARCTRAC comes with all its components enclosed in a waterproof IP65 rated enclosure. Its design also makes use of a 3D position sensor with magnetometer, allowing the unit to know its orientation at all times, meaning that it should be able to automatically position itself from startup. The design also makes use of DC motors with a built in worm gear drive, so the the motors back driving is not possible. 

The system is controlled via a built in Raspberry Pi 3B+ and can communicate with the controlling PC via WiFi. Raspberry Pi's have stable WiFi connections, so we shouldn't see the connection problems that we had with the ESP32 based AntRunner.

Just like the AntRunner, SARCTRAC is only a lightweight rotator with torque specs of 50kg.cm static and 25kg.cm dynamic. So it should be able to handle counterbalanced Yagi beams, and lightweight dish antennas.

The SARCTRAC Mk3b. An Australian designed and made light duty antenna rotator.
The SARCTRAC Mk3b. An Australian designed and made light duty antenna rotator.
SARCTRAC Mk3 Satellite Antenna Rotator Controller and TRACker

KrakenSDR Locates a Repeater Jammer in 1 Hour

Over on YouTubem channel NotaRubicon Productions has uploaded a video describing how a KrakenSDR was used to find the location of a person jamming a repeater site. Amateur radio enthusiasts can utilize VHF or UHF repeater towers, which receive signals from lower power handheld or other radios, and retransmit that signal at high power on a slightly different frequency over a much wider area. Unfortunately malicious people can jam these repeaters by transmitting at the same time as other users, effectively denying use of the repeater by legitimate users.

If you weren't already aware, KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding. We successfully crowd funded the device on Crowd Supply, and the device is currently available for sale on Crowd Supply, Mouser and direct from our website krakenrf.com.

In this video I read the story of how we caught the jammer that had been jamming our GMRS repeater for months, and how by using the KrakenSDR Radio Direction Finder (RF locator), we were at his house in 1 hour.

The KrakenSDR can track a signal being transmitted from 100Mhz to 1Ghz - so I can track ham repeater jammers, GMRS repeater jammers, ham-radio transmitters, GMRS radios - pretty much any transmitter with a signal strong enough for you to receive.

How The KrakenSDR Located Our Repeater Jammer In 1 Hour. Overview of the KrakenRF Inc. RF Locator

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

Internet Archive Seeks Donations of Materials to Build a Digital Library of Amateur Radio and Communications

In Internet Archive is a non-profit project with the main goal of maintaining a historical archive of the world wide web. Its goal is to preserve human knowledge and culture by creating an Internet library for researchers, historians, and scholars. Readers may be most familiar with their 'wayback machine', that allows users to view websites as they appeared in the past.

As part of this project, the Internet Archive is currently seeking donations of materials including printed medium relating to amateur radio and communications to add to their archives. Their press release and contact details read:

Internet Archive has begun gathering content for the Digital Library of Amateur Radio and Communications (DLARC), which will be a massive online library of materials and collections related to amateur radio and early digital communications. The DLARC is funded by a significant grant from the Amateur Radio Digital Communications (ARDC), a private foundation, to create a digital library that documents, preserves, and provides open access to the history of this community.

The library will be a free online resource that combines archived digitized print materials, born-digital content, websites, oral histories, personal collections, and other related records and publications. The goals of the DLARC are to document the history of amateur radio and to provide freely available educational resources for researchers, students, and the general public. This innovative project includes:

  • A program to digitize print materials, such as newsletters, journals, books, pamphlets, physical ephemera, and other records from both institutions, groups, and individuals.
  • A digital archiving program to archive, curate, and provide access to “born-digital” materials, such as digital photos, websites, videos, and podcasts.
  • A personal archiving campaign to ensure the preservation and future access of both print and digital archives of notable individuals and stakeholders in the amateur radio community.
  • Conducting oral history interviews with key members of the community. 
  • Preservation of all physical and print collections donated to the Internet Archive.

The DLARC project is looking for partners and contributors with troves of ham radio, amateur radio, and early digital communications related books, magazines, documents, catalogs, manuals, videos, software, personal archives, and other historical records collections, no matter how big or small. In addition to physical material to digitize, we are looking for podcasts, newsletters, video channels, and other digital content that can enrich the DLARC collections. Internet Archive will work directly with groups, publishers, clubs, individuals, and others to ensure the archiving and perpetual access of contributed collections, their physical preservation, their digitization, and their online availability and promotion for use in research, education, and historical documentation. All collections in this digital library will be universally accessible to any user and there will be a customized access and discovery portal with special features for research and educational uses.

We are extremely grateful to ARDC for funding this project and are very excited to work with this community to explore a multi-format digital library that documents and ensures access to the history of a specific, noteworthy community. Anyone with material to contribute to the DLARC library, questions about the project, or interest in similar digital library building projects for other professional communities, please contact:

Kay Savetz, K6KJN
Program Manager, Special Collections
[email protected]
Twitter: @KaySavetz 

Radio Jove Spectrograph Hardware and Software

NASA's Radio Jove is a project that enables students and amateur scientists from around the world to observe and analyze the HF radio emissions from Jupiter, our Sun and our galaxy using easy to construct HF radio telescopes that receive spectrographs from 16-24 MHz. The project has existed for more than two decades, and these days the telescope builds mostly make use of low cost software defined radios.

In a presentation for the Society of Amateur Radio Astronomers (SARA) Richard Flagg & Jim Sky talk about what sort of hardware is used these days for the Radio Jove project. They note that SDRs like the Softrock, Funcube Dongle Pro+, SDR-IQ, SDR-14, RTL-SDR, and RASDR have been used. They go on to discuss some of the spectrograph logging software that is used with the project as well.

The presentation slides in PDF form can be found here.

Richard Flagg & Jim Sky: Radio Jove Spectrograph Hardware and Software (RJ10/11)

Open Source Military TAK Android App Supports RTL-SDR ADS-B Tracking

ATAK (Android Tactical Assault Kit) is an Android app used by some branches of the US military for visualizing geospatial information such as enemy and friendly positions, as well as any other information of interest. The civilian version of ATAK (CivTAK) was recently open sourced in 2020 and can be downloaded from the Google Play Store.

The software has a huge number of features for coordinating teams, planning operations and visualizing information. It can even network via handheld, or ham radios or a Meshtastic LoRa network if a central server and internet connection is unavailable. Of note is that their plugin page references the possibility of using a plugin that uses RTL-SDR hardware for ADS-B aircraft tracking. However, it appears that the plugin needs to be purchased from tak.gov. We suspect that in the future there will be more RTL-SDR compatible plugins available.

[First seen on Hackaday]

ATAK on an Android Device

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!

SignalsEverywhere: Playing Classic Games over Amateur Radio with NPR-70 TCP/IP Modems

Over on her YouTube channel SignalsEverywhere, Sarah has uploaded a new video that shows us how TCP/IP connections can be made over the amateur radio spectrum using low cost NPR-70 TCP/IP modems that operate in the 70cm amateur band at around 433 MHz.

With a TCP/IP connection available it is then possible to play games over the amateur radio bands and Sarah demonstrates this in action with some classic games like Unreal Tournament 2004, noting that the ping was about 225ms. She notes that she used a lower symbol rate to keep within the legal limits within the USA, however in other regions a higher symbol rate may be possible, resulting in better ping. She goes on to try a strategy game called OpenRA which is a bit more suited to running on low speed high latency networks, noting that the radio TCP/IP connection worked very well.

In the video Sarah also shows what the modem signal looks like on the spectrum and waterfall using SDR++.

Playing Classic Games over Amateur Radio | NPR-70 Modem TCP/IP Unreal Tournament and OpenRA