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The SWLing Post Reviews the YouLoop Passive Loop Antenna

Over on the SWLing (Short Wave Listening) Post blog Thomas has just uploaded his review of the YouLoop in a post titled "The Airspy Youloop is a freaking brilliant passive loop antenna". If you weren't aware, we are currently selling this loop in our store for US$34.95 incl. free worldwide shipping to most countries. Sales are currently in pre-order as our first batch of units ordered sold out within a day, but we're soon going to receive the second batch in the next few days. 

Thomas is a seasoned shortwave listener who has used many antennas, and in the review he notes that he is extremely impressed with the performance. In his review he tests the antenna in a location that is swimming with RFI and places the loop in the middle of a bedroom. Although the situation is not ideal, Thomas was surprised at the number of signals he was able to receive.

To work properly the YouLoop requires a low noise figure radio like the recommended Airspy HF+ discovery, but Thomas notes that he's also had excellent success with the SDRplay RSPdx running in HDR mode.

YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF
YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF

A Homemade Boat Computer with RTL-SDR for Weather Fax, NavTex and more

Over on Hackaday we've seen a post about [mgrouch]'s "boat computer" which consists of a Raspberry Pi 4, HDMI display, and a whole slew of sensors and receivers useful for a marine environment including an RTL-SDR.

The built in equipment includes a GNSS receiver, orientation sensors, AIS receiver, 4G and WiFi, lightning EMI sensor and alarm, optional autopilot integration, rudder angle sensor, connections to boat instruments like wind, depth, speed, temperature, barometric and humidity sensors, an Iridium receiver, and finally an RTL-SDR for receiving weather fax, NavTex, satellite weather, AIS, RTL 433, morse code and more. It really is an "all-in-one" device.

His blog post explains in detail how each of the components work in the system, and in particular for the RTL-SDR he shows how you can use the boat computer to receive FM via GQRX, and NavTex via the Java based Frisnit Navtex decoder. Navtex is a marine radio service that transmits at 518 kHz or 490 kHz. It provides text data regarding weather forecasts, weather warnings, navigational information, and urgent maritime safety messages. For his antenna he writes that he uses a 10 kHz - 30 MHz Mini Whip antenna that he purchased on Aliexpress.

mgrouch's Boat Computer with RTL-SDR
mgrouch's Boat Computer with RTL-SDR

A Comprehensive Lab Comparison between Multiple Software Defined Radios

Librespace, who are the people behind the open hardware/source SatNOGS satellite ground station project have recently released a comprehensive paper (pdf) that compares multiple software defined radios available on the market in a realistic laboratory based signal environment. The testing was performed by Alexandru Csete (@csete) who is the programmer behind GQRX and Gpredict and Sheila Christiansen (@astro_sheila) who is a Space Systems Engineer at Libre Space. Their goal was to evaluate multiple SDRs for use in the SatNOGS ground stations and other satellite receiving applications. 

The SDRs tested include the RTL-SDR Blog V3, Airspy Mini, SDRplay RSPduo, LimeSDR Mini, BladeRF 2.0 Micro, Ettus USRP B210 and the PlutoSDR. In their tests they measure the noise figure, dynamic range, RX/TX spectral purity, TX power output and transmitter modulation error ratio of each SDR in various satellite bands from VHF to C-band.

The paper is an excellent read, however the results are summarized below. In terms of noise figure, the SDRplay RSPduo with it's built in LNA performed the best, with all other SDRs apart from the LimeSDR being similar. The LimeSDR had the worst noise figure by a large margin.

In terms of dynamic range, the graphs below show the maximum input power of a blocking signal that the receivers can tolerate vs. different noise figures at 437 MHz. They write that this gives a good indication of which devices have the highest dynamic range at any given noise figure. The results show that when the blocking signal is at the smallest 5 kHz spacing the RSPduo has poorest dynamic range by a significant margin, but improves significantly at the 100 kHz and 1 MHz spacings. The other SDRs all varied in performance between the different blocking signal separation spacings.

The rest of the paper covers the TX parameters, and we highly recommend going through and comparing the individual result graphs from each SDR test if you want more information and results from tests at different frequencies. The code and recorded data can also be found on the projects Gitlab page at https://gitlab.com/librespacefoundation/sdrmakerspace/sdreval.

YouLoop Batch 2 Available for Pre-Order: Estimated Shipping in One Week

A few days ago we posted about our release of the first batch of YouLoop passive HF/VHF loop antenna kits. We underestimated the demand and sold out of kits in less than a day! We now have a second batch currently being manufactured and it should be ready to ship out in about a week from now (late March/early April).

You can currently pre-order this item from our store, and we will ship it out as soon as the stock hits the shelves on our warehouse. For this product we are focusing on non-US customers and US customers can purchase locally from airspy.us. Though we will still fulfill US orders if you want to order from us instead.

If you are interested in further information, search YouLoop on Twitter to see a bunch of new tweets about people talking about and demonstrating this antenna design.

YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF
YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF

KerberosSDR Now Available from ML&S in the UK

KerberosSDR is now available for sale from Martin Lynch & Sons (ML&S) in the UK for £169.95 incl. VAT. Quantities are limited. ML&S have also created a short overview video shown below.

The KerberosSDR is our 4-channel phase coherent capable RTL-SDR unit that we previously crowdfunded back in 2018.  With a 4-channel phase coherent RTL-SDR interesting applications like radio direction finding, passive radar and beam forming become possible. It can also be used as 4 separate RTL-SDRs for multichannel monitoring.

Virtual Video Visit Episode 4, The Kerberos 4 Coherent SDR new to ML&S

For non UK customers the KerberosSDR is also available from the USA with international shipping from the Othernet store and Hacker Warehouse for US$149.95.

The KerberosSDR: 4x Tuner Coherent Capable RTL-SDR
The KerberosSDR: 4x Tuner Coherent Capable RTL-SDR

Creating an APRS I-Gate and Digipeater with Baofeng and RTL-SDR

Over on YouTube ModernHam has uploaded a video showing how to create an APRS I-Gate and Digipeater with Baofeng and RTL-SDR. He also makes use of a Raspberry Pi as the computing module and an audio cable to connect the Baofeng to the audio jack of the Pi. The tutorial then consists of a walk through of the various software setup steps, and finally how to connect the Baofeng and RTL-SDR to the Pi.

If you weren't already aware, Automatic Packet Reporting System (APRS) is a digital VHF mode used in amateur radio. It allows for packets of data to be sent to receiving nodes over a local area via RF. Typical uses for it are vehicle tracking, weather station telemetry, text messages, announcements and other wireless device telemetry like high altitude balloons. An I-Gate is an internet connected node which receives local APRS RF signals and uploads them to the internet, to be seen on sites like aprs.fi. TX capable I-Gates may also broadcast to the local RF network messages from APRS transmitters on the other side of the world.

APRS I-Gate and Digipeater with Baofeng and RTL-SDR

DragonOS: Debian Linux with Preinstalled Open Source SDR Software

Thank you to Aaron for submitting news about his latest project called "DragonOS" which he's been working on while in COVID-19 lock down. DragonOS is a Debian Linux based operating system which comes with many open source software defined radio programs pre-installed. It supports SDRs like the RTL-SDR, HackRF and LimeSDR.

Aaron's video below shows how to set up DragonOS in a VirtualBox, and he has two other videos on his channel showing how to set up ADS-B reception with Kismet, and how to run GR-RDS in GNURadio. He aims to continue with more tutorial videos that make use of the software installed on DragonOS in the near future.

DragonOS 10 Installer (download in description)

Screenshot of the GR-RDS Tutorial

RTL-SDR AIS Android App Now with Waterfall Display for Frequency Offset Tuning

Thank you to Christian, author of the RTL-SDR AIS Android App for letting us know that he's updated his app and it now includes a waterfall display for tuning the AIS frequency. Tuning the AIS frequency is not required on higher end RTL-SDR dongles that come with a TCXO (Temperature Compensated Oscillator), but cheaper RTL-SDRs will have significant frequency offsets that will require the offset to be determined after a few minutes of warm up time. The easiest way to do this is with a waterfall display as that allows you to tune the frequency manually.

AIS stands for Automatic Identification System and is used by ships to broadcast their GPS locations in order to help avoid collisions and aide with rescues. An RTL-SDR with the right software can be used to receive and decode these signals, and plot ship positions on a map.

RTL SDR AIS Driver App PPM

SDRplay Coronavirus Supply and Distribution Impact Update

SDRplay have recently released an update on how the Coronavirus is impacting their supply lines. In short, they note that their fulfillment is currently normal, but there may be delays in the logistics distribution network. In terms of stock levels, they have enough to cover a few more weeks of normal buying, but beyond that the supply chain is not certain and there may be restocking delays.

Dear customer,

We have been fortunate that our suppliers have been able to source the components needed to fulfil our current backlog commitments. In particular the demand for the new RSPdx exceeded our expectations, and that has caused shortages up until now.

However we now have enough product available to continue supply of all three SDRplay production RSPs for a few more weeks at traditional buying levels. Beyond that, we will be dependent on our subcontract manufacturing partners’ ability to source components. As the coronavirus situation unfolds it is likely that restocking will take significantly longer than usual and we are working with both suppliers and our distributors to do our best to plan for the uncertain future.

Meanwhile, regarding orders placed in the next week or so, SDRplay and its fulfilment centres are currently working as normal, BUT please be aware that logistical delays in the distribution network are likely – so please be patient if your shipment takes longer than expected.

We’d also like to take the opportunity to send our best wishes to all our customers and their friends and families as this emergency situation develops.

Jon, on behalf of the SDRplay team.

YouLoop Portable Passive HF/VHF Loop Antenna now Available in our Store

We have recently been able to obtain a small number of YouLoop HF/VHF portable receive only passive antennas that were produced by the owner of Airspy. The YouLoop is available in our store priced at US$34.95 including free worldwide shipping. It comes with the balun "tee" connector, coax inverter, 2x 1m semi-rigid coax cables for a ~60cm loop, and 1x 2m semi-rigid coax for the feedline. Note that US customers may wish to purchase from airspy.us as they have local US stock. We are focusing on non-US orders for this product and we only have very limited stock at the moment.

YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF
YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF

If you don't know what a "YouLoop" is, it is a simple passive magnetic loop antenna design which consists of a ring of coax cable and a low loss 1:1 or 4:1 balun. The design was recently popularized by Youssef (prog) the owner of Airspy. Many users on Twitter have been reporting good results with HF reception with the design. It appears to be especially useful in urban environments where there is lots of local noise.

Being passive, it has no amplification and so it works best with a low noise SDR like an Airspy HF+. However we have also found decent results with SDRplay SDRs, and a standard RTL-SDR Blog V3 running in direct sampling mode, although RTL AGC mode needs to be turned on for an extra boost. Improved results can be obtained by using a low cost HF amplifier on the front end, and even our wideband LNA which is advertised as working down to 50 MHz still does actually give a decent boost from 5 MHz and up.

Also the design has some advantages in that it has very low electrical interference pickup, and has no electronics that can overload from signals that are too strong. Overloading from strong signals is something that can easily affect cheap magnetic loop antennas like the MLA-30, and even higher end loop antennas too. Being a magnetic loop, it also naturally filters out electric field interference which is extremely common in urban environments, and is the reason why e-field antennas like miniwhips often perform poorly.  

The antenna is designed to be extremely portable, being lightweight and easy to assemble/disassemble. As such it is not designed to be weatherproof, so if you do decide to mount it permanently please make use of weatherproofing tape.

Unlike fixed magnetic loops, the YouLoop design is also easy to experiment with. By using longer coax cables you can easily create a larger loop which can result in stronger signals. We found that replacing the 1m loop cables with 2m lengths gave quite nice results for us. If you have the space you could try even larger loops too. 

The design also doubles as a great VHF antenna with reception up to 300 MHz possible when used in a folded dipole configuration. To do that, simply flatten the loop into a dipole shape.

Finally, if you prefer the YouLoop can also be constructed by yourself. The Twitter post below shows the basic design. Search Twitter for "YouLoop antenna" for more discussion on the design too.

In the future we hope to offer a comparison between other loop antennas like the MLA-30 and Wellbrook.

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