Over on YouTube Amateur Radio VK3YE has uploaded a video showing his 'HF Helper' project. The HF Helper is a tunable HF filter and attenuator that helps improve HF reception when in the presence of strong overloading signals. VK3YE writes:
Using an RTL-SDR.COM dongle (genuine model V4) and a computer with SDR Sharp you can get quite good reception of HF signals. However reception can sometimes be spoiled by overload from signals on or away from the desired reception frequency. The 'HF Helper' presented here can reduce these problems. And you can use it in conjunction with a QRP transmitter to form a simple transmitting station.
RTL SDR HF Helper improves reception
Also as a bonus, in a related video VK3YE also shows the RTL-SDR Blog V4 being used on SDR Touch on an Android phone for portable HF, VHF and UHF reception.
Last week we posted about Alex Petit Jr's 'Project H Line 3D' which is a collection of documents and programs designed to be a beginner's guide to antenna fabrication, reception, recording, software processing, and graphic display of the 21 cm Hydrogen line. The project makes use of an RTL-SDR and LNA as the radio front end.
This week Alex gave an online talk to the Society of Amateur Radio Astronomers (SARA) discussing the project and giving an overview.
Project H Line 3D' is a collection of documents and programs designed to be a beginner's guide to antenna fabrication, reception, recording, software processing, and graphic display of the 21 cm Hydrogen line. The project makes use of an RTL-SDR and LNA as the radio front end.
The Hydrogen Line is an observable increase in RF power at 1420.MHz that is created by natural hydrogen atoms. The Hydrogen line is most easily detected by pointing a directional antenna toward the Milky Way where neutral hydrogen is abundant. Properties of the hydrogen line curve such as its shape and Doppler shift can be used to measure the shape and properties of our galaxy.
Alex's project H Line build is designed to be inexpensive and easy for students to build and set up for drift scans which involve pointing the antenna towards the sky and letting the Earth's rotation drift the Milky Way into and through the view of the antenna.
The project includes a design for a 13-element circular patch feed Yagi that can be built using common materials available from a hardware store. The 13-element Yagi results in about 15dBi gain and a 30-degree 3dB bandwidth.
The software portion of the instructions uses the SDR# IF Average plugin, and uses that to record log files every few minutes. The log files are then converted by an included Java program by Jamison Adcock into a logarithmic dB scale and a format compatible with Rinearn 2D and 3D graphics packages.
We've recently come across an X post by Jamie Vital who notes that he has created a site called armsdr.com which is dedicated to tracking which SDR-related software has support for Windows 11 on ARM64.
The Windows OS is most commonly run on x86 and X64 CPU hardware. However, in recent years Microsoft have been pushing to add support for ARM CPUs as well. ARM CPUs are generally lower performance, but significantly more efficient in terms of power use, so they are excellent for battery-powered devices, and so they are commonly used in devices like phones and single-board computers.
Linux is well supported on ARM CPUs, and recently Apple have begun selling computers with ARM CPUs, the Apple M1 and M2. However, Windows support for ARM is still quite lacking, and not very popular. This leaves people who unwittingly purchase a Windows 11 ARM64 laptop mostly out of luck when it comes to running common SDR programs, as programs written and compiled for x86/x64 CPUs will not run on ARM64.
armsdr.com notes that currently only one program, SatDump, has official Win11 ARM64 support. Other programs like rtl_433 and SDR++ have unofficial support, and pretty much every other program has no support, although some may work in emulation mode. But to complicate matters, for emulation mode to work without dropping samples, you need to use librtlsdr drivers that have RAW_IO enabled.
We note that some developers of programs like SDR++ are also refusing to add official Win11 ARM64 support due to the feeling that Windows on ARM has too many issues to be worth supporting. Combined with how low the Win11 ARM64 userbase is, this is most likely the attitude of most developers. Because of these reasons, we strongly suggest avoiding purchasing Win11 ARM64 machines if you want to run SDR software.
Thank you to Alex Petit Jr who wanted to submit 'Project H Line 3D' which is a collection of documents and programs designed to be a beginners guide to antenna fabrication, reception, recording, software processing, and graphic display of the 21 cm Hydrogen line. The project makes use of an RTL-SDR and LNA as the radio front end.
If you were unaware, the Hydrogen Line is an observable increase in RF power at 1420.4058 MHz that is created by natural hydrogen atoms. The Hydrogen line is most easily detected by pointing a directional antenna toward the Milky Way where neutral hydrogen is abundant. Properties of the hydrogen line curve such as its shape and Doppler shift can be used to measure the shape and properties of our galaxy.
Alex's project H Line build is designed to be cheap and easy for students to build and set up for drift scans which involve pointing the antenna towards the sky and letting the Earth's rotation drift the Milky Way into view of the antenna.
The project includes a design for a 13-element circular path feed Yagi that can be built using common materials available from a hardware store. Alex started with a Yagi design using circular director elements but found these difficult to find and fabricate. However, through NEC antenna analysis software he found that replacing the circular elements with more commonly found and easier-to-fabricate square elements had a negligible effect on the antenna's performance, unlocking a cheaper build. The 13-element Yagi results in about 15dBi gain and a 30-degree 3dB bandwidth.
Plate Yagi gives an almost identical Hydrogen line detection as the Disk Yagi
The software portion of the instructions uses the SDR# IF Average plugin, and uses that to record log files every few minutes. The log files are then converted by an included Java program by Jamison Adcock into a logarithmic dB scale and a format compatible with Rinearn 2D and 3D graphics packages.
Thank you to Jason for writing in and sharing with his his recently released software "mmng-ui" which is a TUI (text user interface) for Multimon-NG. If you were unaware, Multimon-NG is multipurpose decoder software for the RTL-SDR and other SDRs which is capable of decoding pager protocols like POCSAG and FLEX, as well as other common protocols like EAS, AFSK, FSK9600 DTMF, CW and more.
mmng-ui is a front end for Multimon-NG that allows you to view pager messages in a clean-looking text interface. mmng-ui listens on a chosen UDP port for raw streams from software like SDR++, passes that to Multimon-NG, and then displays the results.
Back in 2018 we first posted about JJ's Lego Pi Radio, which was an all-in-one RTL-SDR + Raspberry Pi based FM and internet radio system enclosed in Lego.
More recently JJ has written in again sharing with us some updates to his Lego Pi project. First, he notes that he has now created a webpage showing all his radio builds, most of which consist of an Arduino Nano + Raspberry Pi and RTL-SDR, with most enclosed in Lego builds.
JJ also wanted to highlight his latest build optimized for DAB reception, made from an old Android TV box, RTL-SDR the welle-cli software, and of course a Lego enclosure.
My latest build, a FM / DAB+ / INTERNET / MP3 radio, was not made with a Raspberry Pi but with an older Android TV box flashed with Armbian + Ubuntu.
This was cheaper and allowed me to recycle some hardware that was gathering dust. Besides the board needs less power and best of all, the whole system fits into internal eMMC storage, so no more messing with fragile micro SD card. The only problem I had was with the onboard audio so had to use an inexpensive USB audio dongle. I also connected an Arduino nano through USB to easily control a small LCD display and some LEDs.
The board's IR port works well under Linux so I can control the radio with any cheap infrared remote. But I also made a web interface for a fun way to drive the radio from a tablet, PC or even smartphone.
Back in May, we posted about the upcoming DeepRad, which is advertised as a modular RTL-SDR system, providing RTL-SDR PCB boards without USB and SMA connectors that are seated into a custom motherboard. A few days ago they released their crowdfunding campaign on Crowd Supply.
The individual DeepRad RTL-SDR units are priced at US$80 each, whereas the 'DeepRad Quad' which includes four units and a motherboard is priced at US$340 with free US shipping and $12 intl. shipping for both products. It appears that the idea behind the modular boards is to allow people designing a custom PCB to easily seat an RTL-SDR on their design.
The DeepRad Quad advertises 'Synchronize TCXO', which implies that the four units can run from the same clock. However, we don't see any noise source, distribution, or switching hardware, and no heat management, so we don't expect it to be useful for coherent projects like the KrakenSDR is.
Over on YouTube Baltic Lab has uploaded a video showing how he was able to successfully use an RTL-SDR Blog V4 and the included multipurpose dipole antenna kit to receive images from polar-orbiting NOAA weather satellites.
In the video, Baltic Lab shows how to orient the dipole antenna in a "V-Dipole" shape which optimizes it for receiving from satellites. He also shows how to use a VNA to confirm that the telescopic elements on the dipole are extended to the correct length, noting that he was able to achieve a VSWR of less than 1.2 between the target frequencies of 135 to 138.1 MHz, with a near perfect match at 136.5 MHz.
He then demonstrates receiving the NOAA APT signals with his laptop, and successfully recovering the weather satellite image.
How To Receive Weather Images Directly from Space | NOAA Weather Satellites
