Category: Antennas

Testing a YouLoop on an RTL-SDR Blog V3 with Direct Sampling

Thank you to Frugal Radio for submitting a YouTube video where he tests the YouLoop on an RTL-SDR Blog V3 running in direct sampling mode. The YouLoop is a passive HF loop antenna that requires a highly sensitive SDR like the Airspy HF+ Discovery to work at its full potential. However, in direct sampling mode the RTL-SDR Blog V3 does have enough sensitivity to work with the antenna to some extent thanks to the HF amplifier that is used on the direct sampling circuit. In the video Frugal Radio demonstrates the YouLoop receiving various HF signals.

Will an AirSpy YouLoop work with an RTL-SDR v3 on HF in direct sampling mode? It shouldn't...

We also note a second video by Bartłomiej Marcinkowski which shows an RTL-SDR Blog V3 in direct sampling mode running with a DIY YouLoop and MiniWhip. The MiniWhip does have increased signal strength, but the YouLoop is still usable and may be a better choice in the presence of interference. Later in the video he compares the RTL-SDR Blog V3 with MiniWhip against the Airspy HF+ Discovery with DIY YouLoop. 

RTL-SDR v3 & YouLoop vs RTL-SDR v3 & MiniWhip vs AirSpy HF+ Discovery & YouLoop [80m,40m,20m]

Imaging the Milky Way in Neutral Hydrogen with an RTL-SDR Part 2

Last month we shared information about Job Geheniau's success with using an RTL-SDR dongle to image our galaxy in neutral Hydrogen. Our galaxy is full of neutral Hydrogen, and lots of neutral Hydrogen together results in a detectable radio peak at 1.42 GHz. This peak is called the Hydrogen line. By scanning the galaxy at the Hydrogen line frequency with a 1.5 meter dish on a motorized mount, an RTL-SDR, and a few filters and LNAs, Job is able to create a radio image of our galaxy.

In Job's previous attempt he created an image by pointing the dish antenna at 168 predefined grids calculated to cover the Milky Way, resulting in 168 points of exposure data. In his latest work Job has created an even higher resolution image by taking 903 points of exposure data. Each exposure took 150s and the total 903 exposures took 8 nights to record. Once all data was collected he uses the same process as before, which is to input all the Hydrogen line data into a standard 2D excel sheet, then use conditional formatting to create a heatmap which reveals the image. He then applies a blur and stretches the image into the Mollweide Cartographic which can represent the entire Universe in one image.

Job has shared with us his PDF where he documented his process and shares his images (note 16 MB PDF file). We also share his full resolution images below, just click to open. We think that these images are quite amazing and an excellent achievement for a backyard radio astronomer.

If you're interested in Hydrogen line radio astronomy we have a tutorial that will help you observe the Hydrogen line peak on a budget. The tutorial could be improved upon by motorizing the dish, allowing you to create images like the ones above. You might also be interested in a similar project by Marcus Leech who took 5 months of hydrogen line observations with an RTL-SDR in order to create an even higher resolution image.

Characterizing Yagi Antenna Directionality via ADS-B Reception

Over on his blog Alex Krotz has been investigating whether adding more passive director elements actually affects the directionality of his home made Yagi-Uda antenna. Instead of using modelling software, Alex wanted a more accurate result that took into account all the imperfections of his antenna.

His idea was to receive ADS-B signals with his Yagi and a dipole antenna, then compare the data received in order to determine in which directions the Yagi receives better than the dipole. To do this he first creates a standard 2D map of plane tracks collected over a 24hr period for both the dipole and Yagi. A gaussian blur is applied to the two maps in order to fill in blank space and the data is normalized. Then he simply subtracts the dipole plot from the Yagi-Uda plot. The resulting difference plot reveals a mapping of where the Yagi receives better or worse compared to the dipole in a 2D plane.

Directivity of the Yagi revealed by comparing against a dipole
Directivity of the Yagi revealed by comparing against a dipole

DragonOS: Decoding Iridium Satellites with the Iridium Toolkit and an RTL-SDR

DragonOS is a ready to use Linux OS image that includes various SDR programs preinstalled and ready to use. The creator Aaron also runs a YouTube channel that has multiple tutorial videos demonstrating software built into DragonOS.

In his latest video Aaron explores Iridium reception with an RTL-SDR Blog V3, RTL-SDR Blog Active L-Band Patch Antenna and Iridium Toolkit/gr-iridium. Iridium is a satellite constellation that provides services such as global paging, satellite phones, tracking and fleet management services, as well as services for emergency, aircraft, maritime and covert operations too.

In the video he shows how to edit the config file to turn the bias tee on, how to record Iridium data, how to install the AMBE voice decoder, and finally how to decode the Iridum data with Iridium toolkit and play voice recordings.

DragonOS LTS Decoding Iridium satellites with the Iridium toolkit (gr-iridium, RTL-SDR)

Testing the YouLoop on VLF & LF Reception with an Airspy HF+ Discovery

Over on his YouTube channel Frugal Radio has been testing his YouLoop passive magnetic loop antenna on VLF and LF reception with his Airspy HF+ Discovery. In the video Frugal Radio browses the VLF & LF spectrum, making note of some interesting signals, and showing how well the combo receives.

The YouLoop is a low cost passive loop antenna for HF and VHF. It is based on the Möbius loop design which results in a high degree of noise cancelling. However the main drawback is that it is a non-resonant design, which means that it needs to be used with ultra low MDS receivers like the Airspy HF+ Discovery. We have YouLoop stock available in our shop for $34.95 with free worldwide shipping.

Airpsy YouLoop passive antenna review on VLF & LF with an HF+ Discovery and SDR# during storms!

Open Weather: An Artistic Performance Involving Live NOAA APT Signal Decoding for Sound Arts Festival

Just after our post a few days ago about an art project involving weather satellite reception with SDRs, we received a story submission about an artistic performance with similar weather satellite and SDR themes. The submission from Sasha Engelmann reads:

Open Work, Second Body is a live-streamed performance by designer Sophie Dyer (@sophiecdyer) [M6NYX] and geographer Sasha Engelmann (@sashacakes) [M6IOR] in collaboration with the author Daisy Hildyard. The work was performed twice during Reveil 2020, a global sound arts festival streaming sounds from listening points around the planet on the day of the International Dawn Chorus.

Open Work, Second Body asks: From the climate crisis to coronavirus: what are the tools we need to make sense of events unfolding on vastly disparate scales? Through spoken word, field recordings and live radio reception of two NOAA satellite images, the work probes the porous boundaries between our bodies, local atmospheres and weather systems.

Still image capture from livestream of Open Work, Second Body, AM performance, May 2nd 2020

Due to lockdown constraints in London, Sophie and Sasha were not able to be in the same place or to leave their apartments, so they performed the work via simultaneous streams from their respective balconies in South East and North West London. Using RTL-SDRs, Turnstile antennas, Open Broadcast Software and collaborating with two NOAA satellite passes, Sophie and Sasha shared the process of decoding NOAA satellite images with hundreds of viewers around the world, employing spoken word poetry and field recordings to complicate relationships of local and global, weather and climate, the individual and the collective. 

Recordings of the performances can be found at the links below. 

☀️Morning: [performance starts at 05:25]
🌤️ Afternoon: [performance starts at 05:00]

Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020
Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020

Open Work, Second Body is part of Sophie and Sasha's larger artistic research and design project Open Weather, which employs ham radio, open data and feminist theories and approaches to build new and diverse communities around satellite image decoding and weather sensing. The Open Weather web platform will be launched in Summer 2020 and will host an archive of SDR-generated weather images, visually rich how-to guides for those with no radio and engineering experience, and material about Sophie and Sasha's collaborative artistic practice. 

For Open Work, Second Body, Sophie and Sasha would like to thank the Soundcamp Team: Grant Smith, Dawn Scarfe, Christine Bramwell, Maria Papadomanolaki and Ciara Drew. They are grateful to Daisy Hildyard for her willingness to be in conversation with them, Bill Liles NQ6Zfor technical advice, Jol Thoms for sound design, Rachel Dedman, Laure Selys and Arjuna Neuman (Radio Earth Hold) for early curatorial input, Akademie Schloss Solitude for the support of a residency, the satellites NOAA 18 and NOAA 19 and the RTL-SDR and wider ham radio community.

It's very cool to see technical hobbies like ours starting to make an impact in art and reaching a wider audience. More content and images available on Sophie's Open Weather webpage, and Sasha's Open Weather webpage

Open Weather Live Stream

Tech Minds: Review of the MLA-30 Active HF Loop Antenna

Over on YouTube Tech Minds has uploaded a new video where he reviews the MLA-30 active HF loop antenna. In the past we have posted about the MLA-30 antenna a several times on the blog as it is the cheapest active loop antenna available on the market, can be powered by the RTL-SDR Blog V3's bias tee, and generally loop antennas can give good HF performance in a small package. In the video he compares the MLA-30 against an end-fed halfwave antenna and concludes that the MLA-30 works well at the lower frequencies, but not so well in the higher bands.

MLA-30 Active HF Loop Antenna

Testing out the SDR-Kits L-band Inmarsat Patch Antenna for AERO

The SDR-Kits L-band Patch antenna is a modified GPS antenna designed for receiving Inmarsat satellite stations such as AERO and STD-C. They have another version for receiving Iridium frequencies as well. The patch costs £12.90 inc VAT in UK, or approx US$14 for non-UK customers. 

Over on his channel Frugal Radio has uploaded a video where he tests this patch antenna with an RTL-SDR Blog V3. The built in bias tee on the V3 is used to power the antenna. In the video he shows how he's able to receive and decode AERO using the JAERO decoding software and how he uses a a metal backing to improve reception.

SDR-Kits frugal L-band Inmarsat patch antenna review decoding CPDLC ADS-C with RTL-SDR v3 dongle!