Tag Archives: Mag Loop Antennas

The Airspy Youloop is a freaking brilliant passive loop antenna

Before I start talking Youloop, I have a little confession to make up front:

At the Winter SWL Fest when I gave a presentation about Portable SDR DXing, not only did I give attendees the wrong name of the Airspy Youloop antenna, but I also configured it incorrectly, hence the poor performance via my Miscrosoft Surface Go tablet PC.

I had assumed the the crossover component of the antenna was the transformer component. I realized the mistake I made when I saw some of the first promotional photos of the Youloop antenna a few weeks ago.

The crossover connects both sides of the loop while the tee junction contains the transformer.

Doh! I’m trying to forgive myself for making such an obvious mistake, but in my defence–and in the spirit of full disclosure–my antenna was a very early sample prototype without instructions, diagrams, etc. so I set it up imagining it being similar to the homebrew loop Vlado and I built. (FYI: When I say “Vlado and I built” it, I really mean, “Vlado built it.”) 

So obviously I made a poor assumption.

Once I assembled the antenna correctly? Wow. Just. Wow!

Youloop: The ideal travel antenna for high dynamic range SDRs

The Youloop, Airspy HF+ Discovery, SDRplay RSPdx, and all cables easily fit in my Red Oxx Lil Roy pack.

The Youloop is truly the travel antenna I’ve always wanted for portable SDR DXing. Here’s why:

  • It’s incredibly portable and can be rolled up to fit in a small travel pouch
  • It has all of the low-noise characteristics of other magnetic loop antennas
  • It’s wideband unlike many passive loop designs
  • It requires no variable capacitor or tuner
  • It’s made of quality components
  • It requires no external amplifier nor power source
  • It takes one minute to assemble
  • It’s affordable (~$35 USD shipped)

The only caveat? To take advantage of the Youloop, you must use a high dynamic range receiver.

Airspy HF+ Discovery SDR

I can verify that this antenna works brilliantly with the Airspy HF+ Discovery.

The AirSpy HF+ SDR

It will also pair well with the Airspy HF+  if you shortcut R3 via the R3 modification.

SDRplay RSPdx SDR

I’ve also used it numerous times with the new SDRplay RSPdx while using SDRuno in High Dynamic Range (HDR) mode. With the RSPdx, I can make spectrum recordings of the entire AM broadcast band. Note that HDR mode is only available on the RSPdx at 2 MHz and below, using the SDRuno app.

I have not tested the Youloop with other SDRs yet. I will soon test it with my WinRadio Excalibur.

So how well does the Youloop perform?

Listen for yourself!

I’m doing a little cargiving family members today. Their home is swimming in RFI (radio interference/noise). In the past, I’ve struggled to make good mediumwave recordings at their home–certainly an ideal situation for a mag loop antenna.

This morning, I wanted to record one of my favorite local AM stations (WAIZ at 630 kHz), so I set up the Youloop in the middle of a bedroom, hanging off a large bookshelf set against an interior wall. In other words: not an ideal situation.

When I plugged in the Airspy HF+ Discovery and loaded the Airspy SDR application, I fully expected to see a spectrum display full of broadband noise.

Instead, I saw signals. Lots of signals:

Sure, there’s some noise in there, but it’s low enough I could even do proper mediumwave DXing on most of the band if I wished.

In fact, if you’d like to experience the HF+ Discovery/Youloop pairing in this compromised, less-than-ideal DXing setup, why not tune through one of the spectrum recordings I made?

Click here to download the spectrum file [885.7MB .wav].

The recording was made on March 30, 2020 starting around 10:50 UTC. You’ll need to open this file in AirSpy’s free application SDR# or a third party SDR app that can read AirSpy .wav files.

I can’t wait to try the Youloop in other locations. Since we’re in lock-down due to Covid-19, I won’t be able to try the Youloop in a hotel any time soon. Almost all of my 2020 travel plans have been canceled.

Highly recommend

If you have one of the SDRs mentioned above, go grab a Youloop. At $35 USD, it’s a fantastic deal.

Click here to check out the YouLoop at the RTL-SDR.com store ($34.95 USD shipped).

Click here to check out the YouLoop at Airspy.US ($29.95 + shipping).

Click here to search for AirSpy distributors in your region/country.

If you don’t have a high dynamic range receiver, note that Airspy is exploring the idea of making a pre-amp for the Youloop. If interested, you might drop them a note of encouragement!

Do you have a Youloop? Please share your comments!


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Coastal DXing with the AirSpy HF+ Discovery and a homebrew passive loop antenna

Last week, we packed the car and headed to coast of South Carolina.

The trip was a bit impromptu but through the creative use of hotel points, we scored a two bedroom ocean front unit with a fantastic little balcony.

The vacation gave me an excuse to test the new passive loop antenna my buddy Vlado (N3CZ) helped me build recently.

The loop design came from AirSpy’s engineer and president, Youssef Touil.

This passive mag loop takes advantage of the new AirSpy HF+ Discovery‘s exceptionally high dynamic range. Youssef had reported impressive results, so I had to build one.

Vlado had a length of Wireman Flexi 4XL that was ideal for this project. The only tricky part was penetrating the shielding and dielectric core at the bottom of the loop, then tapping into both sides of the center conductor for the balun connections.  Being Vlado, he used several lengths of heat shrink tubing to make a nice, clean and snag-free design.

The results were truly exceptional. I spent most of my time on mediumwave from the hotel balcony because I was determined to catch a transatlantic signal.

Check out the spectrum display from my Microsoft Surface Go tablet:

Our ocean front hotel was inundated with noise, but I still managed to null out most of it and maximize reception using the passive loop. I simply suspended the loop on the balcony rocking chair–not ideal, but effective and low-profile.

Want to take a test drive?

If you’d like to experience this portable SDR setup, why not tune through one of the spectrum recordings I made?

Click here to download the spectrum file [1.7GB .wav].

The recording was made on November 17, 2019 starting around 01:55 UTC–I chose it at random and have yet to listen to it myself. You’ll need to open this file in AirSpy’s application SDR# or a third party SDR app that can read AirSpy .wav files.

Stay tuned…

I’m writing an in-depth report of the HF+ Discovery, my experiments with this setup and AirSpy’s soon-to-be-released passive loop antenna for the January 2020 issue The Spectrum Monitor magazine. Spoiler alert: I am truly impressed with the wee little AirSpy HF+ Discovery. It’s a powerhouse!


Do you enjoy the SWLing Post?

Please consider supporting us via Patreon or our Coffee Fund!

Your support makes articles like this one possible. Thank you!

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“G8JNJ Reverse Engineers and Reviews the MLA-30”

Many thanks to SWLing Post contributor, Paul, who shares the following story from the RTL-SDR.com blog:

Last month we posted a collection of reviews about the MLA-30 which is a budget magnetic loop antenna designed for receiving HF signals. The overall consensus from the reviews was that it worked decently for the price, but of course could never live up to the high end loops that cost hundreds of dollars.

Recently Martin (G8JNJ) reverse engineered the active circuit used on the loop from photos taken by M0LMK and has made some observations on it’s performance, noting that it’s design isn’t very good. First he notes that the amplifier chip is a Texas TL592B two stage video amplifier which isn’t that great for this application. His measurements show an OIP3 of 20dBm, a P1 saturation of -3dBm and a noise figure of 12dB.

Of interest, he explains that the creator of this loop has designed it poorly as the impedance match of the loop to low pass filter is very wrong, resulting in a very poor amplitude/frequency response. He shows how the response can be improved with a few termination resistors, but is still not great.[…]

Click here to read the full article at RTL-SDR.com.

 

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Marty needs advice as he builds a passive magnetic loop antenna

Many thanks to SWLing Post contributor, Marty Kraft, who asked that I share the following question with our community:

I’m still working on a receive-only passive hula loop magnetic antenna for my Tecsun PL-660.

After viewing thousands of YouTube videos (LOL), I built the PVC-pipe structure [you can see in the photo below].

But I need some tech help to finish…

The antenna is 90 inches tall; large loop diameter is 40 inches; and small loop diameter is 17 inches. The wiring is 14 gauge braided.

I plan to put the antenna outside on the porch. Then I’ll run coax from the small loop to the receiver inside and use a 365 pF air variable capacitor to tune the large loop.

My first question is, what’s the best coax to use for the 10-ft run from the small loop to the radio inside? Second, will that 365 pF cap tune the entire 3-30 MHz range?

It’s hot here in Louisiana, so I’d really like to tune the capacitor from inside my apartment, also using coax to connect the cap to the large loop. Will that work? Or does the cap have to connect directly to the large loop?

Any other tips or suggestions? Thanks for the help!

Post Readers: If you have any helpful advice for Marty, please comment!

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David reviews and compares the MLA-30 magnetic loop antenna

Many thanks to SWLing Post contributor, David Day (N1DAY), who has completed a thorough review of the MLA-30 loop antenna. In this review, he compares the MLA to the Wellbrook ALA1530-LF and a 30 foot square ground loop antenna.

In short, he finds that the MLA-30 performs fairly well on the AM broadcast/mediumwave band, but can’t compete with the Wellbrook otherwise–especially in terms of noise floor. David also noted that “the MLA-30 had a very serious issue with IMD and in some cases, stations that were clearly heard with both the Wellbrook and the ground loop were totally obliterated by IMD when switching to the MLA-30.”.

Click here to read David’s full review on his blog, Ham Signal. 

Click here to view the MLA-30 on eBay.

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LZ1AQ Evaluates Impact of the Height Above the Ground on Mag Loop Performance

Source: LZ1AQ

Many thanks to SWLing Post contributor, Harald Kuhl (DL1AX), who shares the following article on LZ1AQ’s website:

Published on: 2018/11/20, Rev. 1.0 July 2018, Rev. 1.1 Nov 2018

Author: Chavdar Levkov LZ1AQ

Setup

Two identical small loops were placed one above the other according to Fig.1. One of the loops is very low – almost on the ground. The other one is placed at height which usually is used by the loop users. Two AAA-1C wideband active antenna amplifiers were used. Their gain difference was not more than 0.3 dB. The feeder was FTP cable each 20 m long. No cable baluns were used. The outputs were connected through two way antenna switch to a SD RX (Perseus). I used a measurement technique described in – A Periodic Switching Technique to Compare Receiving Antenna Performance in the Presence of Strong Fading. This is a precise method to compare two receiving antennas with real sky wave signals and the resolution can be less than a decibel. The idea is to switch periodically between two antennas and to estimate their difference on a calibrated graphic strength meter of a SD radio.[…]

Click here to read the full article.

I’ve often assumed height had little effect on the performance of an HF loop antenna–this evaluation seems to support that theory. Thanks for sharing this, Harald!

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