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.
In 2019, shortly after Icom announced the Icom IC-705, I speculated that this rig might be a contender for “Holy Grail” status.
I must admit…the more I use this radio, the more I love it. It is a proper Swiss Army Knife of a radio. Even though I’ve owned and operated it for a few months, I still haven’t explored all that it can do, and I keep finding features I love.
After completing the upgrade, I hooked the ‘705 up to my main antenna and worked a few Parks On The Air (POTA) stations off of the supplied battery pack (instead of a power supply). While I worked on other projects in the shack, I checked the POTA spots and work a few stations with a whopping 5 watts of output power.
After a couple hours on the air (mostly listening), the internal battery pack still had a good 60-70% capacity.
At one point, I tried a little daytime mediumwave DXing and cruised past 630 kHz which some of you might already know is the home of one of my favorite hometown radio stations, WAIZ.
From my home, WAIZ is a tough catch, so it was weak, but I could hear it.
This reminded me that I had made a recording of WAIZ with the IC-705 when in my hometown earlier this month.
Normally, I pull the MicroSD card out of the IC-705–which almost requires needle nose pliers and is one of my few complaints about this rig–and view the files on my PC or MacBook, but I was curious if perhaps the IC-705 software had a built-in file display.
Of course it does!
Simply press the MENU button, then the RECORD button on the touch screen, and you’ll see the following selections:
Press “Play Files” and you then see a list of folders organized by date:
Click on a folder and you’ll see a list of recordings made that day:
These are some of the most important pieces of information I use to index my audio recordings and the IC-705 does this automatically. In fact, if you allow the IC-705 to gather its time information from the internal GPS, the time stamp will be incredibly accurate.
The only thing I add to the file name after export is the broadcaster name/station callsign.
If that wasn’t enough, if you touch one of the recording files, the IC-705 will open it in an audio player:
The built-in player displays the meta data, and even includes a number of controls like fast-forward, rewind, skip to next or previous file. and pause.
I’m sure this is the same audio player found in the IC-7300, IC-R8600 and other late-model Icom SDR rigs. But in a portable battery powered transceiver? This is a genius feature.
As I type this post I’m listening to the audio from the WAIZ file shown above. I can imagine when I’m able to travel again (post-pandemic), how useful this will for one-bag air travel.
Not only is the IC-705 a QRP transceiver and wideband multi-mode general coverage receiver, but it’s a recorder and audio player with a built-in front-facing speaker. I can set this transceiver at my hotel bedside and listen to recordings I made in the field earlier that day or week.
Keep in mind that the IC-705 is an expensive radio–certainly one of the most pricey QRP radios ever produced at $1,300 US (at time of posting although I’m sure we’ll start seeing lower pricing this year). But if you’re an SWL and ham, you’ll find the IC-705 is the most versatile portable transceiver on the market. If you’re an SWL only, you can disable the transmit on the IC-705 and essentially have a portable battery-powered SDR receiver with built-in audio recording and playback with color touch screen spectrum and waterfall display.
Despite the price, this is Holy Grail territory in my book.
Icom IC-705 Review
If you subscribe to The Spectrum Monitor magazine, you’ll be able to read my (4,000 word!) review of the IC-705 in the upcoming February 2021 issue.
Many thanks to the folks at KMTS who share the following:
A studio version of the KMTS Boot Up Special of 17.1.2021 on 7780 kHz at 0100 UTC. This transmission consisted of Country and Western sounds, engineer test signals, rare re-media mixes of cult radio favourites, strange tones, and vox.
Rebroadcasts: 7 pm eastern time Sunday January 17th 2021 and Sunday January 24th 2021 (0:00 UTC Monday 1/18 and 1/25 on 9395 kHz.
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!
Many thanks to SWLing Post contributor, April TimeLady, who shares her latest collection of Japanese language WebSDR recordings–this time, for December 2020. April notes:
Please find in this email a link to another batch of SDR recordings I have uploaded on archive.org that I made over the course of December.
I concentrated mostly on mediumwave stations to get Christmas music, and I also have New Year’s recordings in it too. I also have shortwave recordings too, but not as much as I have in the past few months.
Shortwave Radio Audio Archive contributor, Tom Gavaras, shared this studio recording of Radio Moscow from January 1, 1980. We posted this recording on the SRAA, but I also wanted to share it here as I’m sure there are readers who might have even heard this show over shortwave live back in the day.
I’m certain anyone familiar with Radio Moscow during the Cold War also remembers the voice of Joe Adamov. Enjoy:
Thank you for sharing this recording, Tom!
Happy New Year!
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