Many thanks to SWLing Post contributor, Grayhat, who shares the following modification he made to a Noise-Cancelling Passive Loop antenna last year. He’s kindly allowed me to share his notes here, but apologized that at the time, he didn’t take photos of the project along the way and recycled many of the components into yet another antenna experiment.
Cut the R1 (0 Ohm resistor – jumper) so that the center tap of the transformer won’t be connected to ground, then solder a short piece of wire to the tap.
The first pic (top) shows the balun seen from top side, the arrow indicates the small hole going to the transformer tap.
This pic shows the bottom of the board with the trace to cut and the spot for soldering the tap wire (needs cleaning with a bit of sandpaper to remove the cover paint). The solder is as easy as 1-2-3 once the trace is cut and the spot cleaned just insert a wire from the top of the board and solder it to the bottom and there you go!
Build the NCPL using “fat” coax (RG8 will do) with the top cross connection.
NCPL modification schematic
Side note: the top “cross connection” is the weak point, so it would be a good idea putting a short piece of (say) PVC pipe over that point, the piece will also help suspending the loop or sticking its top to the support pole, as for the feedpoint, a small electrical junction box will fit and protect the tiny balun from bad weather
Now the difference: connect the two center conductors of the NCPL to the balun input and the braid to the wire going to the center tap (as above).
Such a configuration will give some advantages over the “standard” NCPL one. The loop will now be galvanically isolated from the feedline/receiver so it will have much less “static noise.” Due to the tap, the typical 8 pattern of the loop will be preserved, this means that the loop will now have much deeper nulls.
By the way, the balun could just be wound w/o buying it. I suggested the nooelec since that way anyone with little soldering ability will be able to put it together. Oh and by the way it’s then possible adding a small preamp at the balun output if one really wants, any preamp accepting a coax input will work. 🙂
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.
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!
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Magnet Wire Vertical Loop Antenna
For those of you in a noisy condo like me, the environment does not give me many options. I was experimenting with a YouLoop on the wooden porch with somewhat acceptable results. For its size, it is an excellent performer, especially on the lower bands. Here is a very interesting review of the YouLoop, including close-up pictures of the innards of the phase inverter and 1:1 balun, by John S. Huggins. However, it is not waterproof and I was concerned about the ice and snow ruining it. I could tape up the connectors with waterproof tape but I also wanted something with a bigger capture area. A magnet wire stealth antenna might be just the thing!
I just happened to have a waterproof 1:1 ATU balun from Balun Designs that I was going to use for future Amateur Radio use whenever I get around to passing the next level test; it is total overkill for what I intended to use it for. It would make a good connection point and (this one) also acts as an RF choke as well. One can make a 1:1 balun by buying the right Type of ferrite core and winding it yourself. Here is just one idea from Palomar Engineers.
So I dusted it off, went to a local store to get a 100 foot spool of 26 gauge magnet wire and tested it strung up around my living room. It came out to be a rectangle about 42 feet in circumference. Results were usable. I expected lots of noise and there is a great deal across the bands, so only the strongest shortwave stations were received. However, I was surprised by how strong the mediumwave band was and good to listen to without an amplifier.
I am ambivalent towards trying to perfectly match the impedance since this is a broadband receive-only antenna and the impedance will vary greatly over MW and SW bands. And I don’t want to mess with a remotely controlled tuned loop since this antenna was destined for the outdoor porch. I tried a Cross Country Wireless preselector at my desk but had some mixed results. I later found out, by disconnecting things in series, that the preselector inline raised the noise level about 5 dBm, so I took it out for now. Perhaps it needs more internal shielding or the connecting cable is bad.
Polarization is an issue, too. I have read that most man-made noise (QRM) is vertically polarized, so why would I use a vertically oriented loop? Then I saw David Casler’s video on loop antennas where he explains that connecting a vertical loop antenna at the bottom or the top makes it horizontally polarized (connecting the coax on the side makes it vertically polarized). I never knew that! Horizontal polarization will mitigate some of the offending QRM as well as match the polarization of mediumwave band transmitters. Furthermore, I read that a horizontal loop will have poor signal pickup at low frequencies because it is not high enough off the ground, similar to a horizontal dipole. For now, a vertical loop connected to facilitate horizontal polarization is what I want.
A note about wire size. People make a big deal about it but those are mostly amateur radio people. Transmission depends on efficiency so things like wire size, skin effect, standing waves, and other things matter (see here, for example). With a receive-only antenna it is OK to use very thin wire. Resonance can matter if you want the last ounce of signal strength with an antenna tuner, like in high-Q type loops where the bandwidth is very narrow and you are using a multi-turn loop with variable capacitor and a pick-up coil of wire to the receiver. Comparatively, my simple loop is depending more on a single turn of wire, the aperture size, length of wire for its performance, and carefully isolating the feedline coax using RF chokes at both ends.
Here is one example of a strong station from Cuba I was able to record because WLW was off the air for some unexpected reason.
Radio Reloj, Cuba 870 kHz (At the end, you can hear WLW come back online with CBS news):
Side note about Radio Reloj on Wikipedia, the strange format seems to fit well with a totalitarian regime, including a “corrector” who “corrects the content/writing errors to meet the requirements”. Read the wiki link for yourself. Not a society I want to live in, thank you very much!
Example of 80 meter band performance – Greetings to a new person from members of the “Awful, Awful, Ugly Net”, 3855 kHz:
Encouraged by the results, I “installed” the magnet wire around the support beams of the wooden porch, wrapping it carefully to create a square loop. Holding it in place is a brick at each bottom corner since I am not allowed to nail anything into the Association-owned porch. The length came out to about 32 feet (8 feet per side), so I trimmed it and connected to the balun. I also added an RF choke at the Airspy HF+ input from Palomar Engineers which helped bring noise down a couple of S-units. That might not sound like a lot but by also shutting off the living room air filter and an AC switch with “wall-wart” AC power adapters on it, I was able to reduce the noise a little bit more. There is still a lot of noise from the neighbors, so it is not a perfect situation.
Here are two examples of reception with the outside installation.
Side note about the Radio Newsletter. I stumbled on it when using the YouLoop and found that some of the content is very interesting and informative. Of course it is geared mostly towards amateur radio but some of the news items are of general radio interest as well. It airs 1pm Saturday through 2am Sunday, USA Central Time. Obviously, many segments repeat during that lengthy timeframe and reception depends on propagation from Missouri.
KDDR 1220 kHz, West Fargo, ND station ID (presumably “nighttime” power of 327 watts):
The shortwave bands are still a noisy disaster but signal levels are higher compared to the YouLoop. Only the strongest stations come in like WRMI, WHRI, Radio Espana, Radio Habana, and CRI. And I can hear the loudest amateur radio operators.
Just for grins, here is Radio Rebelde on 5025 kHz when band conditions were above average:
Another phenomenon I am looking into is the reception pattern of a vertical loop. Less than 1/10th wavelength, the null is through the center of the loop. At one wavelength, the null manifests in the plane of the wire loop. They are too close to phase them but switching between two directional loop antennas might improve reception depending on frequency. We shall see in the future.
At least for now, I have a decent mediumwave band which performs better than the useful CCrane Twin-Ferrite amplified loop antenna that was used in the (noisy) indoors, I can hear the 160 & 80 meter amateur bands better, and the reception of the strongest shortwave broadcasters are more predictable. Not bad for four dollars of wire!
Brilliant, Tom! Again, I love how you’ve not only made an inexpensive antenna, but you’ve even done it within your HOA regulations. You’re right, too: if you’re not transmitting into an antenna, it blows the experimentation door wide open! Thank you once again for sharing your project with us.
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Loop on Ground Part 2
My previous Loop on Ground (LoG) experiment was useful which entailed connecting my Wellbrook loop amplifier to a 100 foot loop of speaker wire in the field at my favorite local Forest Preserve. It really brought in stations I had never heard before or strong stations in a more powerful way that made the audio really pleasant to listen to. This report will describe more experiments with smaller wire loops to see what the limitations are. 100 feet of wire is quite a lot of wire to mess around with especially in the cold weather or public places that do not have as much private space.
I don’t understand all the electrical interrelationships but a long posting at RadioReference.com had a great discussion about creating a 160-20 meters LoG receive-only antenna. It is 11 pages long but is worth reading how “nanZor” experimented with various parameters for general use. Kudos to him for documenting the findings as the design changed over time. You can find it here:
nanZor basically boils it down to a few guidelines.
Keep it on the ground. Lifting the wire more than an inch or two decreased the lower angle signal reception greatly.
Calculate the optimal length for one full wavelength of wire at the highest target frequency, say for example, the top of the 20 meter band (14350 kHz). 936/14.350 MHz * 0.9 velocity factor of simple insulated wire = 58.7 feet. You can round up to 60 feet, no big deal since this is broadband. The antenna should have a predictable reception pattern from 1/10th wavelength up to 1 full wavelength. Outside that range, the pattern gets “squirrely”.
Using a 9:1 balun seemed to be a little better than a 4:1 balun at the antenna feedpoint. This gets into things I cannot measure and has to do with rising impedance as a loop gets closer to ground level. I am not sure but I think my Wellbrook amp has a built in 4:1 balun and it seems to work just fine.
Make sure to use an RF Choke at BOTH sides of the feedline coax cable. He was adamant that the loop can get easily unbalanced and allow noise into the antenna and/or feedline and so it must be isolated and the ground allowed to “float” in his words.
Personally, I also wanted to use less wire and happened to have a length of 42 feet of landscape wire which should work well below 5 MHz with the Wellbrook amp engaged. Results were not bad even though on hard frozen ground. Signal levels were down a little compared to the 100 foot of wire. Here are a couple of examples, first one in a fast food parking lot with a grass field next to it and second at the usual Forest Preserve parking lot on a grass field. I made sure that my car blocked the view of the wire so people would not get nervous!
La Voz Missionaria, Brazil:
Voice of Welt from Issoudun France in Kurdish:
These are not necessarily “DX” but definitely good for SWLing. I like the signal strength with the amplifier inline at the antenna feedpoint and I did not have to use an RF Choke at the receiver side as was suggested.
I had a 75 foot long insulated wire and used that at the Forest Preserve parking lot on a couple of different days. Lower frequency signal strength and signal/noise ratio improved a little bit to be noticeable.
Examples below with the 42 foot loop and 9:1 balun/choke, no amplifier:
KSDA, Agat Guam in English
WB8U doing a POTA activation of Leavenworth State Fishing Lake
VOLMET weather, Shannon Ireland
HCJB Quito Ecuador, probably in Quechua
As a side note, there is a posting that mentions low-angle DX is better with regions that have better “ground conductivity”, salt water being the best. I have no way of verifying this. See post# 126 by KK5JY Matt.
So, bottom line is that a Loop on Ground can be useful for pleasant SWLing and portable. Best to use it on grass, not asphalt. The loop amplifier is useful to get signal levels up if you have to use a smaller loop size but the signal/noise ratio will suffer due to its smaller aperture. And, warning, the public will find a way to trip over the wire no matter where you set it up (I may try putting the wire around my car if I can park on a grass surface and/or use the gaudiest, brightest neon green or orange wire I can find – they can’t trip over THAT, can they?).
Thanks, Tom, for sharing your update. Obviously, the LoG is working brilliantly. It’s amazing that you got such clear reception from the parking lot of a fast food restaurant. If you were using a vertical instead, I bet signals would have been buried in the noise.
I can also relate to people tripping over antenna wires. I remember one POTA activation recently (the first activation in this three park run) where I intentionally laid my counterpoise on the ground, off a foot path, in the brush and where I couldn’t imagine anyone ever stepping. Ten minutes into the activation and for no reason, someone walked off the path, into the brush, and it snagged them. Maybe I’m just a Ninja level trapper and never realized it!?
Thanks again for sharing the results of your LoG, Tom. Inspiring!
I also read somewhere that for transmitting, a LOG antenna is useless as it radiates much of the energy right into the ground! But I didn’t care about that. I needed something for receive I can deploy easily without supports and take down just as easily. As you may recall, my home condo is literally saturated with noise and I cannot null it out. So a wire looped on the ground is supposed to work? You bet it does!
Of course, there are some conditions to meet. There has to be enough flat ground away from people or pets (or lawn mowers!) who would get tangled in the wire on the ground. The wire should be as close to the ground as possible (although I had good results laying the wire on top of cut grass). The loop of wire can vary in circumference from about 20 feet to 150 feet (the shorter length will stay in an omnidirectional pattern higher in frequency but lower in signal pickup and vice-versa for the longer length). The wire needs to be insulated. That’s about it!
So, off to the hardware store to buy a cheap spool of 100 foot 18 gauge speaker wire. But, the articles mention using a balun and they all made their own. I did not feel like doing that (I am not that good at making things from scratch) and I did not want to spend money ordering one. More reading somewhere informed me that my existing Wellbrook Medium Aperture loop amplifier has a built-in balun at the antenna side of the device. Hallelujah!
I bundled together the wire, Wellbrook parts and battery supply, small laptop and Airspy HF+ to my favorite Lake Nelson Forest Preserve. The shelter there is little used and is adjacent to the prairie with cut grass. It did take a good 15 minutes to lay out the 100 feet of wire on the ground while trying to keep it as flat as possible. And I did not have enough space for a circle, so I ended up with an oblong shape. The long sides are facing directly north-south, so in theory (I think) this gives me an oblong shaped reception pattern east-west. The photo shows half of the wire laying on the grass.
I ended up with this setup on a picnic table at the rear end of the shelter. The coax wire goes from the Wellbrook amp into its power module, then to a Cross Country Wireless preselector, then to the Apirspy HF+ and laptop.
I was really impressed by the signal strength of the usual suspects like Radio Nacional da Amazonia. I could see that the Wellbrook amp was boosting signals across the board with only a little extra noise.
I use the preselector to try to keep the Airspy radio from overloading, especially mediumwave broadcast signals which can sound like a small amount of extra “hash” type noise in the background. I have since added into the accessory chain an old Kiwa Electronics BCB filter that does a great job of knocking down the frequencies below 2 MHz.
I have also since added a water resistant box to enclose the Wellbrook amp to keep it safe from getting stepped on or too wet.
Also, a couple of weeks later I was able to go to a campgound and try out 60 feet of wire but the result was noisier since I was surrounded by RV vehicles in a crowded campsite. It was not horrible and I was able to listen to some good radio stations but location can matter with any antenna.
I hope you like the recordings below. Because of some serious health issues this summer, these May 31 2020 recordings & report are just being published now (I am recovering slowly but surely!). My small laptop is under-powered, so I was only able to record MP3 files one at a time. It kept me busy as I went from one frequency to the next and kept recording anything I heard. I was able to hear a couple of stations I never heard before and that is a success in my book.
It remains to be seen if this antenna is as good as my 19 foot vertical antenna attached to the top of the car roof, especially low-angle DX signals. Maybe you will have the chance to experiment as well and share your experience, too. Now, will a small loop-on-ground antenna around my car parked late at night at a far corner of the grocery store work OK??? I will have to try it!
Recordings (crank up the volume if it is too weak):
22:00 UTC, Radio Saudi (Arabic) 11915 kHz
22:04 UTC, KDSA Adventist Radio (Indonesian) 11955 kHz
22:14 UTC, KDSA Adventist Radio (English) 12040 kHz
22:20 UTC, Voice of Korea (Japanese) 11865 kHz
22:23 UTC, Yemen Radio (heavily jammed) 11860 kHz
22:35 UTC, Radio Brazil Central (Portuguese) 11815 kHz
22:50 UTC, WWV booming in 10000 kHz
23:11 UTC, UnKnown (might be FEBC) 9795 kHz
23:15 UTC, China Radio Int’l (Spanish teaching Chinese, from Kashi) 9800 kHz
23:17 UTC, China Radio Int’l Business Radio (from Xianyang) 9820 kHz
23:19 UTC, China Radio Int’l (Chinese from Urumqi) 9865 kHz
23:21 UTC, Voice of Korea (Korean) 9875 kHz
23:23 UTC, Maybe Radio Taiwan without jamming from CNR 9900 kHz
23:34 UTC, China Radio Int’l (Chinese from Bamako Mali) 7295 kHz
23:43 UTC, Radio Nacional da Amazonia 6180 kHz (& 11780 kHz around 40 seconds)
23:50 UTC, MAYBE China PBS from Xinjiang in Kazakh (nothing else listed on schedules) 6015 kHz
23:56 UTC, Radio Mali (French announcer humming to music and acting crazy) 5995 kHz
00:30 UTC, XEPPM Radio Educacion (Spanish Mexico City) 6185 kHz
This is brilliant Tom! Thank you for sharing.
Our antenna guru contributor, Grayhat, has been encouraging me (understatement!) to build a Loop-On-Ground antenna but I haven’t done this yet because, at home, our driveway would interfere with its deployment. That and I have no RFI to speak of in my rural/remote home so my skyloop antenna is tough to beat. But having one available for portable use would make a lot of sense. I’m going to put this on my 2021 project list!
Post Readers: Do you use a LoG antenna at home or in the field? Please comment!
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.
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!
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