Category: Antennas

SWLing Blog: Building a Homemade YouLoop (Noise-Cancelling Passive Loop) Antenna

Over on the SWLing Post Blog Thomas has uploaded an excellent tutorial showing how you can build your own YouLoop (aka a Noise-Cancelling Passive Loop). If you've been following our previous posts you'll know that we recently started selling the "YouLoop" which is designed and produced by Youssef from Airspy. The YouLoop is a passive loop antenna designed for HF reception, but also works well up until VHF. The main catch is that you need to use it with a receiver with a low noise figure front end, like the Airspy HF+ Discovery (SDRplay units should work well too). The RTL-SDR Blog V3 in direct sampling mode does somewhat work with it to an extent, but RTL-SDRs relying on upconverters for HF will probably see poor results.

We are selling the loop in our store for $34.95 including free shipping to most countries. Batch 2 is currently in preorder, but is almost sold out and should begin shipping soon. Batch 3 will also be available for preorder soon and is about 2 weeks away from shipping. We also expect there to be a high quality pre-amp available for sale in a few months too which will help those with higher noise figure radios or longer feed line runs. 

Alternatively, as the YouLoop is a relatively simple and openly shared design it is possible to homebrew your own if you want to. Over on the popular SWLing Post blog, author Thomas has written up a full tutorial on hombrewing your own. The parts you need include coax cable, a BN-73-302 wideband 2-hole ferrite core, magnet wire, heat shrink tubing and electrical tape. The guide takes you through the process of winding the balun and constructing the loop using simple tools and a soldering iron.

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

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

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 - UPDATE: Now out of stock. We have reordered more and should be back in stock by end of March.

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, and he has put up a page explaining how the design works here. 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.

Building an Underground Earth Probe Antenna for 0 – 14 MHz TX/RX

Thank you to Jean-Marie Polard (F5VLB) for letting us know about his work in creating underground "earth probe" antennas that work for both RX and TX between 0 - 14 MHz, and are especially good at VLF and below. He writes:

Can't install an antenna at home? Madame refuses the masts, taut son? One solution, The Earth probes antenna.

Our group (https://www.facebook.com/groups/earthprobes/) started in January 2019. At first everyone made fun of me, the professionals called me crazy and today with more than seven hundred members, we installed underground antenna systems and the results are there.

Between 0 and 14MHz, in transmission and reception, it works!

This system dates from 1914/1918 but has been brought up to date.

It doesn't take much to get started, just the urge to try.

Mad of vlf - elf - ulf ? come here https://www.facebook.com/groups/VLF.ULF.ELF/ nearly 1000 members are waiting for you.

So when? Welcome everyone.

To access the Earth Probes and VLF.ULF.ELF groups you'll need a Facebook account. The groups contain a number of research papers documenting the concept, and the photos section. From the photos, an earth probe antenna appears to consist of two long grounding rods spread over a distance, or a grounding rod and long buried wire, combined with a balun.

An example of an underground antenna setup from a 1935 shortwave magazine.
An example of an underground antenna setup from a 1935 shortwave magazine.

Sign up to be an Early Beta Tester of CENOS Antenna Design and Simulation Software

CENOS are a company specializing in 3D modelling and simulation software for induction heating applications. However, they are now branching out and are creating software for antenna design and simulation. Final pricing of the software is not yet advertised, but they write that it has been made affordable thanks to "open source algorithms". Hopefully it will be affordable to hobbyists, but judging by the heat simulation software pricing it may not be (although they offer to software free to students, researchers and teachers).

However, it appears that they will soon be running a beta testing program that should hopefully be free to use during the testing phase. You can sign up to their email list and wait for their announcement on their website.

CENOS Antenna Design Program Screenshots
CENOS Antenna Design Program Screenshots

Techminds Reviews a HF RX SWL Antenna for Small Spaces and Apartments

Over on his YouTube channel TechMinds has uploaded a video reviewing the X1-HF 1 - 50 MHz Trapped Coil Receiving antenna from Moonraker.eu which goes for £69.95. This is a small electrically short antenna for HF reception which is easy to setup and install, requiring no radials. However, like all short HF antennas it is a compromise.

In the review he uses an SDRplay RSP2 SDR to test HF reception with the antenna. Later in the video he also tests it outside the advertised 1 - 50 MHz range. He concludes that the antenna works very well for it's small size.

HF RX SWL Antenna For Small Spaces And Apartments RTL SDR

SATSAGEN: Software to use a PlutoSDR as a Tracking Spectrum Analyzer

Thank you to Frank, HB9FXQ for submitting news about a new Windows program called SATSAGEN which allows you to use a PlutoSDR as a wideband spectrum analyzer. SATSAGEN was created by Alberto IU1KVL and is entirely free to use. This makes it possible to get wideband scans of RF components like filters and attenuators. Together with a directional coupler it could also be used to measure the SWR of antennas as HB9FXQ demonstrates in his Twitter post.

The PlutoSDR is a low cost RX/TX capable SDR with up to 56 MHz of bandwidth and 70 MHz to 6 GHz frequency range. It is typically priced anywhere between US$99 - US$149 depending on sales.

In the video below Alberto demonstrates SATSAGEN performing some wideband scans, and he shows the various features of the software. He writes that the system has a scan range from 70 MHz to 6 GHz and can show results in dBm. The spectrum analyzer works with the TX part of the PlutoSDR to provide a tracking generator with resolution of up to 1024 points. The software can also use the PlutoSDR as a frequency generator with 1 kHz of resolution.

There is also a support group available at groups.io/g/satsagen.

SATSAGEN Screenshot
SATSAGEN Screenshot

SATSAGEN BASICS