Tag Archives: Mag Loop Antennas

Mike Harwood explores active magnetic loop antennas with SDRplay

Many thanks to Jon Hudson with SDRplay who shares the following announcement:


Introducing a new series of videos comparing the performance of wideband active loop amplifier/antennas for HF frequencies and below. In this introductory video, Mike Harwood shows how an RSPduo enables a real-time comparison of two antennas – in this demo, he uses a Wellbrook 1530AN and one of his own compact loop creations. You can see that he has lined up several other active loop antennas/amplifiers to try in future videos, including the Bonito Megaloop FX, the LZ1AQ amp and the Cross Country Wireless amp.

SDPlay will endorse antennas which work well and formally recommend them on its website antenna suggestions page: https://www.sdrplay.com/antennasuggestions/

This is one of many videos from SDRplay – makers of the RSP family of SDR radios. See the full list of SDRplay videos and applications documents on: https://www.sdrplay.com/apps-catalogue/

The RSP family of SDRs from SDRplay cover 1kHz to 2 GHz with no gaps and give up to 10MHz spectrum visibility.

SDRplay is a UK company. The RSP SDR receivers are made in the UK and can be purchased for worldwide delivery directly from http://www.sdrplay.com/ (click on purchase and select your country to view shipping costs) or you can buy from any of our worldwide resellers listed here: http://www.sdrplay.com/distributors/ Many of the resellers offer local free shipping and/or local language technical support.

The SDRplay YouTube Channel is: https://www.youtube.com/c/SDRplayRSP

Spread the radio love

The Chameleon CHA RXL amplified wideband loop antenna

A few weeks ago, Chameleon Antenna sent me a pre-production model of their new wideband magnetic loop antenna called the Chameleon CHA RXL.

I’ve evaluated and reviewed a number of Chameleon’s ham radio antennas (primarily on QRPer.com). I find that the quality of their products are second to none. Price-wise, they tend to be at the top of the market, but keep in mind they machine and manufacture all of their antennas here in the US and they’re incredibly rugged; indeed, military-grade. And in the spirit of full disclosure, I’m proud Chameleon has been a sponsor the SWLing Post and QRPer.com since last year. My sponsors are by invite only and focus on companies I trust with our radio community’s business.

When Chameleon shipped the CHA RXL to me, it wasn’t from their factory, it was directly from the field: Fort Irwin, to be exact.

(Source: NTC Operations Group, Ft. Irwin)

This CHA RXL sample had been used by NTC Operations Group Fort Irwin (who, incidentally, won QRPX this year–click here to read the PDF report).

I was told that the condition of the antenna could be very rough after the QRPX because it had essentially been sandblasted in the desert winds. I was also told that someone accidently transmitted 5 watts into it at some point but it didn’t seem to harm it (for the record, like all amplified receive-only loops, it’s not designed to take RF).

Tony (W0NTC), who was one of the Ft. Irwin radio ops, sent me this note as he dropped off the shipment at Fort Irwin’s FedEx:

“Had a blast with [the CHA RXL], and it was absolutely critical while I was operating in the Army HF Low Power Competition (think tons of high powered MARS stations piling up and drowning out the 20W or less competitors). It absolutely crushed some localized RFI from a huge building I operated behind, and the receive on it I can only describe as “layered” in that I could hear stations somewhat clearer than usual if they transmitted simultaneously. Receiver I used was the IC-705 with default Auto Notch and Noise Reduction.”

Tony volunteered all of this info–I never asked him how it performed.

A few days later, I wasn’t sure what to expect when I opened the box although I knew that my operating locations were nowhere near as cool as its position next to a Humvee at Fort Irwin in the photo above!

I pulled the CHA RXL out of the box and it looked cosmetically flawless to me.

Frankly, there’s not a lot to get damaged. The 36 inch diameter loop is made of rigid aluminum and has a Navy gray powder coating.  The preamplifier unit is completely sealed and made of a high-impact plastic/PVC type material. The steel loop is attached to the preamplifier loop flanges with wing nut connectors.

The only potentially vulnerable part of the antenna system is the  Bias-T box which would normally be located in your shack close to your receiver.

If I mounted the CHA RXL permanently outdoors, I would use Coax Seal around the BNC connection point, of course.

Although the CHA RXL has a supplied mounting bracket for permanent installations, I love the fact that the preamp box has a 1/4” x 20 threaded camera socket on the bottom. This makes for a brilliant portable loop because it can so easily be mounted on a standard heavier-weight tripod! All antenna manufacturers should give us tripod mount options when possible.

On the air

One of the reasons amplified receive loop antennas have become so incredibly popular over the past couple of decades is because they do an amazing job mitigating radio frequency interference (RFI) a.k.a. “QRM.” If you live in a neighborhood with significant radio interference, you really should consider some form of loop in your antenna arsenal.

Ironically, at home, I live in pretty much an RFI-free zone. I’m surrounded by tens of thousands of acres of national forest, so I’ve only used amplified loop antennas in the past for mediumwave DXing–mainly, when I wanted to take advantage of their amazing ability to null out unwanted signals.

Many years ago, I purchased a Pixel Loop Pro antenna (now under a different name via DX Engineering), mounted it outside where it lasted almost a year before a bear decided to pull it down and chew through the coaxial feedline. He/she did so with enough energy that it ripped down the loop and damaged the connector end of the Pixel’s pre-amp. This all happened when our family was travelling for two months in Canada. Why bear, why?!? But I digress…

The CHA RXL version I was shipped has one single rigid loop–the “EU” version’s loop comes in two pieces (for easier shipping/transport)–but I had no problem fitting the entire assembled loop in the back seat of my Subaru or my truck (as long as no one was sitting back there at the time). If you plan to travel with your loop a lot, consider the “EU” version!

I’ve taken the CHA RXL to my parent’s home a couple of times and enjoyed doing a little mediumwave and shortwave listening. Inside the house, the loop would attenuate RFI nicely, but when outside it would all but eliminate many sources of RFI.

At their house, I primarily used my Icom IC-705 for cruising the bands (being careful, of course, to disengage the transmit function).

Listening time in my hometown, though, was very limited. Since the CHA RXL is so portable, I decided to set it up at home on our porch for a few days, giving me an opportunity to test both the Sangean ATS-909X2 and Tecsun H-501x with an external antenna.

I’ve especially appreciated using the CHA RXL on mediumwave. Even from our screened-in porch, I can rotate the loop and use its excellent nulling properties to pick out multiple station IDs on crowded frequencies.

I’ve spent time on shortwave, too, and found that it certainly gave these two portables a signal boost.

In fact, it was by using the CHA RXL that I discovered the audio level difference between AM and SSB on my ATS-909X2 is very minimal when an external antenna is connected.

I’m sure you’ll hear the CHA RXL in action when I post audio clips and recordings in upcoming reviews.

Summary

If I owned a CHA RXL loop, one of the first things I’d do is build a power cord for it with an in-line fuse and terminated with an Anderson Powerpole connector. Since the operating voltage of the Bias-T is 12-14 VDC, it would pair perfectly with one of my Bioenno LiFePo4 batteries, offering a power source with longevity in the field–ideal for a group LW/MW/SWL DXpedition.

It’s difficult for me to truly comment on the loop’s performance because I don’t have another loop at present for comparison. I can say that it’s amazing on mediumwave, where I’ve spent much of my listening time this past week. I believe shortwave reception has been at least on par with my former Pixel Loop, if not better. It’s hard to say, in truth, because propagation conditions have been so poor lately. The CHA RXL loop does effectively mitigate noise!

I’m not sure if the CHA RXL is currently on backorder or not, but I would suggest you check out the product page on Chameleon’s website and possibly contact them if you’re interested. They’ve a number of options and accessories to consider.

Click here to check out the CHA RXL at Chameleon Antennas ($490 US).

One thing for sure: this must be one of the most rugged and durable RX loop antennas on the market. In addition, that Navy gray powder coating helps this rigid aluminum loop disappear against the sky. I believe you could strategically mount this loop and the friendly neighborhood association may never notice–it’s pretty stealthy. Speaking of which…

Josh’s CHA RXL install and demo video

Josh over at Ham Radio Crash Course recently installed a CHA RXL on his house and tested it on several bands, comparing it with a number of his external antennas:

Click here to watch on YouTube.

Spread the radio love

Giuseppe is impressed with the performance of his homebrew passive loop antenna

Many thanks to SWLing Post contributor, Giuseppe Morlè (IZ0GZW), who shares the following:

Dear Thomas, I’m Giuseppe Morlè from central Italy, the Tyrrhenian Sea, Formia.

Today I tested my noise canceling loop inside the radio station by comparing it to the crossed loops. Again, like my medium wave T Ferrite, this loop proved to be very quiet, practically immune to house noise.

You can see my two videos about listening to the Voice of Turkey and a QSO on 40m. between radio amateurs–a test with two different powers, one high in AM and another much lower among radio amateurs.

Here are the videos from my YouTube channel:

Click here to view on YouTube.

Click here to view on YouTube.

A nice result knowing that we are receiving inside my radio station. The homebrew NCPL antenna you encouraged me to build is truly amazing.

Best wishes to you and the SWLing Post community.

73 by Giuseppe Morlè IZ0GZW.

Thank you so much for taking the time to share your thoughts and these videos with us, Giuseppe. It is very encouraging that we have some antenna options that help us cope with all of the RFI generated within our homes! Thank you again!

Spread the radio love

The new Chameleon CHA RXL amplified magnetic loop antenna

Many thanks to SWLing Post contributor, Chris Rogers, who writes:

Hi Thomas,

An interesting new product has just been released for pre order, a US made Chameleon model CHA-RXL receive loop covering from 137 kHz -30 MHz.

Looking at the options it comes on the web page it mentions a Loop type ”US single section” or “two sections European”. I am not sure of the difference however. In the specifications it claims a 36” loop.

However a very interesting new antenna to compete with the likes of Wellbrook, W6LVP etc

Hopefully you may, or one of your readers get one for review.

https://chameleonantenna.com/shop-here/ols/products/cha-rxl

Thank you, Chris!  I do plan to check out and review this loop from Chameleon. I’ve been evaluating a number of their ham radio field antennas and  can say that the quality is simply military grade.

I’m guessing (and it is truly a guess) that the EU version of the antenna is simply in two sections to save the customer excess shipping charges based on the package dimensions.

Thanks again for the tip.

Spread the radio love

Bruce compares two homebrew NCPL antennas to the Airspy Youloop

The Airspy Youloop

Many thanks to SWLing Post contributor, Bruce (VE3EAR), who writes:

I decided that more testing of the Noise-Cancelling Passive Loop (YouLoop) antenna was needed, but I wanted to start with a clean page.

I built two identical loops using some 3/8 inch heliax scraps I had on hand. Both are one metre in diameter and employ the same feed arrangement, with a balun wound on a half inch square binocular core of type 75 mix. There are four turns on the antenna side and eight on the feed line side, of #24 gauge plastic insulated wire. The feed line shield connects to the antenna shields. The only difference between the two antennas is at the top of the loop, opposite to the feed point. One has a simple one inch gap in the shield, with the centre conductor passing across the gap, while the second one uses the crossover connection of the YouLoop design.

I’ve been running some A-B comparison listening sessions, both mid-day and in the evenings after local sunset. The testing is done outside, with the antennas hanging on a low limb of a maple tree in front of the house. The feed line is about twenty feet of coax which connects to my Realistic DX-440 receiver on the front porch. Testing is done listening to the AM broadcast band and the 160, 80, and 40 metre ham bands, with the loop aligned both E-W and N-S and about one loop diameter off the ground.

Both loops work well, but I do have to give the nod to the YouLoop (by Airspy), which produces a stronger signal of two S-units higher than the conventional loop. It also has deeper and sharper nulls, which can sometimes produce total nulling of the station!

73, Bruce, VE3EAR

Thank you so much, Bruce, for sharing your findings with us! I, too, have found that the Youloop generally outperforms my homebrew NCPL antenna. I believe one of the reasons for this as Youssef at Airspy once told me is because the Youloop has a lower loss transformer than anything that can be wound by humans (0.28 dB)–this improves gain.

Click here to read our review of the Youloop and click here for step-by-step instructions on building your own Noise-Cancelling Passive Loop antenna.

Spread the radio love

Giuseppe’s cross-loop experiments

Many thanks to SWLing Post contributor, Giuseppe Morlè (IZ0GZW), who shares the following:

I’m Giuseppe Morlè from Formia, central Italy, on the Tyrrhenian Sea.

I wanted to share with you and friends of the SWLing Post community this antenna project of mine dedicated to those who do not have enough space on the roof or in the garden to install antennas.

These are two separate loops, with two different diameters, one 60 cm, the other 90 cm, each with two variables for tuning … the system is able to receive from 3 to 30 MHz.

I joined these two loops in an opposing way, better to say crossed that can communicate with each other due to the induction effect that is created between the two small coupling loops that are placed one under the other at the top.

In the videos you will be able to see how the antenna system receives. I can use one loop at a time, to detect the direction of the signal or I can use them together for a more robust signal and in an omnidirectional way.

I really like experimenting with the induction effect and you can see that even when closed at home the two loops do a great job.

From my YouTube channel:

I’m not a technician but I really want to experiment to try to listen as well as possible.

Thanks to you and CIAO to all the listeners of the SWLing Post community.

Giuseppe Morlè iz0gzw.

Very cool, Giuseppe! I must say I’ve never tried dual loop experiments like this where one can experiment with the induction interplay. I imagine this could give you some interesting nulling capabilities if you have an unwanted station interfering with a target low-band signal. Thank you again for sharing!

Spread the radio love

Bill’s first DX contest using a Panasonic RF-2200 and a hombrew diode/loop radio

Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD), who shares the following guest post:


My First DX Contest

by Bill Hemphill, WD9EQD

Being a recent new member of NJARC, this is my first time competing in this contest.  I have always been a big fan of BCB DXing and have recently got back into it – especially with the amateur radio bands being in such poor conditions.  The acquisition of a couple of Loop antennas plus two Panasonic RF-2200 radios have just enhanced my enjoyment.

For the contest, I used two completely different radios.  First was the RF-2200 and second was a spur of the moment creation.

The RF-2200 was its usual good performer. While the RF-2200 has a beautiful built-in rotating bar antenna, I enhanced it with the 27” Torus-Tuner Loop Antenna as made by K3FDY, Edmund Wawzinski.  I think I had picked this antenna up at one of NJARC’s swap meets.  So I wish to thank whoever it was that was nice enough to bring it and sell it at the meet.  I have really enjoyed using it.  With this setup, I was hoping that I might be able to pull in Denver, Salt Lake City and maybe even a Mexican station, but it was a complete bust on them.  But I did have a nice surprise in receiving the Cuban station Radio Enciclopedia on 530 in addition to the usual Radio Reloj time signal station.  Following is photo of it in operation:

Originally, I had thought that my second contest entry would be done with a 1962 Sony TR-910T three-band transistor radio.  This radio has a fairly wide dial along with a second fine-tuning knob which would be a big help.  I would have again used the 27” hula-hoop antenna.

But I made the nice mistake of running across Dave Schmarder’s Makearadio website:

http://makearadio.com/

Dave’s site is a wonderful resource for creating your own Crystal, Tube, and Solid State radios as well as Audio Amplifiers and Loop Antennas.  While going down the rabbit hole of his site, I ran across his Loop Crystal Set, #19 Crystal Radio:

http://makearadio.com/crystal/19.php

What grabbed my attention was the wood frame loop antenna which is similar to one I had acquired a couple of years ago at a ham fest:


It was a really nicely constructed, nice swivel base.

I replaced the tuning capacitor with one that has a 6:1 ratio.

At this point I started thinking that I could create something similar with my loop.

I randomly grabbed a diode from my parts box.  Not sure what the exact model is.  (I later found out that it was an IN-34 which is what I was hoping it was.)  Then quickly soldered the diode, a resistor and capacitor to a RCA plug:

I then proceeded to use some jumper cables and just clip it to the tuning capacitor on the antenna base:

The RCA plug was then the audio out (I hope) from the radio.

I quickly realized that I did not have a crystal headset or any headset that would reproduce any audio.  So I used an old Marantz cassette recorder to act as an amplifier.  Fed it into the mic jack and then tried to listen to the monitor out.  Bingo – I could pick up or local station on 1340 really weak.

So I then fed the audio from the Marantz into a Edirol digital recorder.  Now I was getting enough audio for the headphones plus could make  a recording of the audio.

At last I was receiving some signals.  To boost the audio some more I removed the resistor from the circuit.

I found out the I could only tune from about 530 to 1350.  I probably needed to clip the lead on one of the loop turns, but I really wanted to see how it would do at night.  I spent several hours and was just totally amazed at how well it performed and how good the audio was.  The hardest part was when there were very strong signals on the adjacent frequency.  What I found really interesting was that it was not linear in its tuning.  At the low end of the band the stations were more spread out than at the higher end.  This made tuning fairy easy at the low end and very touchy at the high end.  I was able to hear a couple of Chicago stations along with Atlanta and St. Louis.

Here’s photo of it in action:

I have created an audio file of the station ID’s heard with the diode/loop radio.  The audio file is on the Internet Archive at:

https://archive.org/details/bcbstationidsondioderadio

I had a lot of fun in the contest and especially enjoyed trying something really different with the diode/loop radio.  Now I have a whole year to try to think up something really creative for next year’s contest.


Absolutely brilliant, Bill! I’m so happy to see that your ham fest homebrew loop has served you so very well in a contest. I love how you pulled audio from your homebrew, make-shift diode radio as well–using your audio gear in a chain for amplification obviously worked very well.

Thanks so much for sharing your experience, Bill!

Spread the radio love