Back in 2017 we posted about Adam 9A4QV's simple V-Dipole antenna design which works very well for receiving NOAA and Meteor weather satellites at 137 MHz. This type of antenna is a lot easier to build compared to a QFH or turnstile, and it results in good performance if built and set up correctly. Over the years he notes that he's received a number of questions asking to clarify the design and so he's uploaded a YouTube video which explains the built and dimensions of the antenna clearly.
Over on YouTube Tech Minds has uploaded a new video where he unboxes and tests a YouLoop HF Passive Loop Antenna with his Airspy. The YouLoop design is also known as a Möbius loop, or noise cancelling passive loop "NCPL". The passive nature of the antenna means that highly sensitive radios will work best with it, however limited results may still be obtained with other radios. The advantages are extremely low levels of interference pickup and high portability.
In the video Tech Minds explains the specifications of the antenna before demonstrating the antenna receiving the HF bands with an Airspy + SpyVerter. He also tests the loop on VHF, demonstrating its ability to receive a distant 2M beacon.
We note that we sell official YouLoop antennas on our store for $34.95 including free shipping to most countries.
John from JR Magnetics has written in and wanted to share his Kickstarter for a US$50 ultra wide band antenna that he has designed. The size is a just little bit bigger than two credit cards and the advertised coverage is from 750 MHz up to 6 GHz with a VSWR of less than 2.0.
John's Kickstarter text reads below:
I was never satisfied with the commercially available wide band antennas. They were all too large or did not have suitable VSWR over the frequency range generally required by SDRs. I read many research papers and ultimately made a omni-directional ultra wide band antenna, but it was too expensive for most people. Details regarding that antenna can be found at https://www.rtl-sdr.com/constructing-a-3d-printed-wideband-900-mhz-to-11-ghz-antenna/
However, a bi-directional antenna was good enough for most people, so I have made a flat one. The antenna I ended up with is 5 inches by 4 inches and about 3 mm thick with an SMA connector. It is quite definitely not a square patch antenna, which usually has a narrow bandwidth.
This antenna has a VSWR measured to be under 2.00 from around 750 MHz to over 3 GHz. It simulates to have a VSWR under 2.00 out to over 6 Ghz. This is enough for most of the available SDRs. It works very well with WiFi, Bluetooth, Zigbee and other systems within the bandwidth.
The log antenna, Figure 2, has a wide bandwidth, but it is specified as having ranges, because the VSWR rises over 2.00 several times over that range. The antenna measure sover 40 centimeters long, which is problem for me in a laboratory setting. It is too large to fit anywhere and wants to be permanently fixed to a pole or something like that.
The other antenna I have is a discone type device, Figure 3. It is huge. There is not practical for it to fit on a lab bench around various RF devices. It is measures around 28 centimeters at its base. It needs to be elevated above any ground planes, which complicates a laboratory environment with metal bench tops. I have it sitting on a shelf above the computer monitors on the opposite side of the room away from the lab bench. This does not work well when I am trying to deal with wireless devices connected to USB hubs on the bench with short range features.
Figure 4 shows the Flat Antenna next to the Log Antenna for a size comparison that illustrates just how much space saving there is with this new device. This is no small feat. This Flat Antenna is useful around all manner of RF devices on the bench without causing space issues, getting in the way of instruments and couples well with all of the wireless devices I am using. It is small enough with a convenient shape for moving it around and keeping it above a metal bench top. It only needs to be a few centimeters above any ground planes when perpendicular, not horizonal.
Due to its size and shape, near field problems have not been a problem, as with the other antennas. The antenna is quite directional, which is not much of a problem, since the RF bounces around all over the place. A Faraday shield is the only way to keep this device from picking out everything in the vicinity. The neighbors IoT devices create mountains of RF clutter. This antenna picks up all of it. If you only want restricted bandwidths, band pass and reject filters can be used. The load impedance is 50 Ohms across the band making an excellent match for all of the filters I have here.
Figure 5 shows the VSWR as measured by the NanoVNA Version 2. It only goes out to 3 Ghz. The device must be calibrated before use, or you will get extraneous results. I am told the VSWR never goes above 2.00 until after 6 GHz. This is a remarkable antenna. I never found anything comparable to it on the Internet.
It can be used for all wireless and SDR applications normally within the 750 MHz to 6 GHz bandwidth. This is not guess work or speculation. The network analyzer shows the response clearly.
The antenna is 5 inches long by 4 inches wide by roughly 3 mm thick, not counting the SMA connector.
What You Get
You get one (1) antenna, as shown in Figure 1, for each US$50. You cannot do this yourself for that price. Your time alone is worth more than that after you do the calculations, simulations and prototyping. You also would have to deal with fab shops to get this done correctly, which is not always convenient for many people.
In other words, this is a remarkable Ultra Wide Band Antenna at a remarkable price.
This has already been done. I have a Masters Degree in RF Engineering. I also have all of the simulation tools that are not available to most people, with the exception of some university students.
I have sources that I use all the time. I just put this one into the queue. We also have a minimum order, which is why we Crowd Fund this operation.
Once in the queue, it takes about two (2) weeks. After that, we are only concerned with delivery time. We intend to use ordinaty Postal Service mail, to keep the cost down, so time of delivery may vary depending upon the destination.
Risks and challenges
We already have laboratory results, so there is nothing to risk in performance. The only other thing that could be troublesome is the lead time by the vendor that manufactures the main component or any delays caused by the Postal Service.
UPDATE 16 Dec 2020: John has provided us with this document that addresses a few questions people had about the antenna.
In this episode of Frugal Radio's series of SDR beginners guide videos he discusses some antenna basics. He shows the most common types of antennas, provides several tips to help improve reception, and shows how to properly tune antennas using online calculators.
Near the end of the video he shows our multipurpose dipole antenna kit and shows how to adjust the telescopic elements for best reception. He demonstrates that simply extending the elements to the maximum length does not result in the best tuning, rather you need to tune the element length for the frequency being received to get the best results.
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.
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.
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.
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.