Tag Archives: Mag Loop Antennas

How to build a Milk Crate AM Broadcast Loop Antenna

Many thanks to SWLing Post contributor, James Townley, who shares the following guest post originally posted on his Shortwave/Medium Wave blog:

540 kHz to 1700 kHz Loop Antenna (Click to enlarge)

AM Broadcast Loop Antenna

by James Townley

Several years ago, I became interested in medium wave DXing. One of my limitations was the size of my yard, so I developed an interest in tuned loop antennas to compensate, because setting up a beverage antenna was out of the question. I experimented with different sizes of loops, and found that the bigger the aperture, the more gain the loop would have. The tuned loop antenna is also very directional, which allows you to reject, or null out interference from either noise or other stations. Loops are considered bi-directional in that they receive to the front and back, but not to the sides. The tuned loop antenna quickly became my weapon of choice for medium wave DXing.

Recently when the weather began allowing me to enjoy the outdoors, I decided to make another smaller loop antenna from a plastic milk crate I had lying around. I saw the idea on the internet when I observed that someone had used a milk crate for their loop. Click here to see a variety of tuned loop antennas that others have made. Whichever material you decide to make your loop antenna from, just make sure that it is not a conductive material. Wood, plastic, and cardboard seem to be popular materials for loop making. In the photo above, I am using my Sony ICF-2010 to listen to WCCO on 830 kHz. This station is nearly 200 miles south of me, but I am able to receive it with 9 LEDs lit on my signal strength meter while using the loop. There is no direct connection of the loop to the radio, it is inductively coupling with the radio’s own ferrite rod antenna.

If you are interested in making a loop antenna like mine, here are the materials you will need:
120 ft of 18ga insulated wire (I bought a 100 ft spool of cheap speaker wire and pulled the 2 conductors apart):

1 – Plastic milk crate
1 – 15 to 365 pF air variable capacitor (found in many old radios, or a google search to buy one from an internet store)
1 – Tuning knob. Any knob will do as long as it fits the shaft on the variable capacitor.
1 – Tape or wire ties. I used tape to secure the wire while winding, then hot glue when finished.

When you begin to wind your coil, use tape or a wire tie to secure the wire, and leave about a foot of wire. This extra foot of wire will later be soldered to the frame on the capacitor. As you wind your coil, pull the wire snugly and with each turn leave about a quarter inch spacing between each turn. The spacing isn’t critical as long as the spacing is consistent.  I wound 21 turns on my crate. This may differ for you, depending on the size of your crate, or the value of you capacitor. If you find that the bottom frequency isn’t low enough, you can add more wire to make a few more turns. This will lower the bottom frequency for you.

After winding the coil, you can solder each end of the coil to your capacitor. The beginning of the loop gets soldered to the frame of the capacitor, and the other end of the coil to the rotor solder lug on the side of the capacitor. If you do not have a soldering iron, you can use alligator clips to connect your loop coil to the capacitor as well. I secured my capacitor to the inside corner of the crate with hot glue. I put a generous amount of the hot glue onto the bottom of the capacitor frame, and held it to the crate until the glue cooled enough for the capacitor to stay on it’s own. I used enough to get the job done, but not so much that it interfered with the plates in my capacitor. The hot glue seemed to adhere very well. I then checked the spacing of my coil turns, and secured them with the hot glue as well.

I was very impressed with the results after spending some time with the loop. It’s small enough to maneuver around easily, but big enough to give it some gain, so I can listen to daytime DX. I may make another tuned loop using two crates to see how much more gain I get with the larger aperture.

Happy DXing,
James Townley

Many thanks, James, for sharing your project with us! This loop appears to be relatively simple and accessible even to those with little knowledge of soldering or homebrewing. I’m now wondering how a loop made of four milk crates might perform!

Click here to view James’ Shortwave/Medium Wave blog.

The W6LVP magnetic loop antenna

Many thanks to SWLing Post contributor, Troy Riedel, who asks:

Just curious if you or anyone you know have any experience with Magnetic Loops from W6LVP? […]Here’s his eBay page – 458 feedbacks and 100%.

Thank, Troy! I’ve never used the W6LVP loop, but the price–in comparison with other wideband mag loop receive antennas–is very attractive.

W6LVP currently offers two models of loop antennas:

Here’s the product description of the Mag Loop with Power Inserter from the W6LVP website (where orders can also be made–pricing identical to eBay):

The Wellbrook Model ALA1530LN-2 and DX Engineering (Pixel/Inlogis) Model RF PRO-1B magnetic loops are both good amplified receive antennas.  However, they are both expensive.  Shipping the Wellbrook antenna from the UK to the US adds another $100.

Extensive side-by-side testing of the Wellbrook, DX Engineering, and W6LVP receive loops was compiled using simultaneous WSPR signal-to-noise reception reports on all LF, MF, and HF amateur bands.  In addition, extensive laboratory bench tests measuring gain, signal-to-noise ratio, and IMD were also performed.  Signal-to-noise ratio is important to pull weak signals out of the noise and IMD is important to reject distortion caused by nearby strong transmitters such as AM broadcast stations.  In both test regimens, all three antennas performed very well and without significant difference.

The antenna version listed here includes a power inserter for use with receivers or with transceivers that have a separate receive antenna input.  If your rig doesn’t have a receive antenna input, check out my antenna with a transmit/receive switch.

If you live in the shadow of one or more high-power AM broadcast transmitters, contact me about a special version just for you.  Please contact me at lplummer@vcnet.com.

W6LVP amplified receive-only magnetic loop antenna (boy is that mouthful):

  • The W6LVP mag loop is a complete receive antenna system delivering top-of-the-line performance to amateur radio operators and SWLs – particularly for those with space and/or budget limitations.  It is a great complement to vertical or wire transmit antennas.   You have a knob to turn up the power but don’t have one to turn up the received S/N.
  • Ten foot circumference (approximately 1 meter diameter) loop.  Small size yields a natural stealth for HOA challenges.  The loop is rigid enough to maintain its shape but flexible for portable transport or attic installation.
  • Includes a low-noise, broadband amplifier covering 2200 (135 kHz)  through 10 meters (30 MHz) with no tuning or adjustment.  Perfect match for continuous tuning SDR receivers.  Great for contesters to quickly check all bands.  Greater coverage is possible at reduced performance.
  • Light-weight antenna structure fabricated from furniture-grade PVC yields a strong but very light antenna weighing only 2 pounds (not including power inserter or power adapter).  Great for both portable/camping as well as fixed installations.  Light weight and small size make for lower shipping cost – particularly compared to shipping from the UK.
  • Directly compatible with a low-cost speaker tripod stand (not included) for portable operation.
  • Compatible with light-duty rotator (recommended) for fixed operation.  Loop can be rotated to null interference by up to 30 dB or enhance desired signals.
  • Includes low-noise linear AC power adapter to generate clean 12 volts for the loop amplifier.  Unlike the DX Engineering antenna which requires 24 VAC, power can be easily supplied by 12 volt batteries during portable operation.  Reverse polarity and short circuit protection provided by automatically resettable fuse.

Eham reviews are very positive–so far, 5 stars on all six reviews.

I also discovered this short video of W9OY comparing the W6LVP loop to a full size 80 meter vertical (verticals are much more susceptible to noise than loops):

Click here to view on YouTube.

I am very curious if any SWLing Post readers have ever compared the W6LVP loop to the Wellbrook or Pixel Loop antennas.

I actually own the Pixel Loop and might very well purchase, review and compare the W6LVP loop later this year (if time allows).

If you own the W6LVP loop and/or have compared it with the Pixel or Wellbrook, please comment!

Click here to view W6LVP antennas on eBay.

Click here to view the W6LVP website.

Klaus demonstrates his folding mag loop antenna

Many thanks to SWLing Post contributor, Klaus Boecker, who follows up after our recent post showcasing his homebrew magnetic loop antenna.

One of the cool things about Klaus’ antenna is that he can easily position it vertically (see above), or fold it over into a horizontal position (see below).

While one would think Klaus would get optimal performance from his loop while vertically-oriented, it’s not always the case. Klaus has discovered that on some frequencies, placing the antenna in the horizontal position lowers the noise level and increases the target signal’s strength.

To demonstrate, Klaus made the following short video for us:

Click here to view on YouTube.

That’s a pretty amazing difference, Klaus! I’m no antenna expert, but perhaps what’s happening is you’re eliminating noise that is polarized in the plane of your antenna, thus the signal “pops out” much better when oriented horizontally?

I’m curious if any readers can explain this.   I know very little about loop antennas–especially small loops since so much of their surroundings affect their performance.

Thanks for sharing, Klaus!

Klaus’ magnetic loop antenna in “urban camouflage”

Many thanks to SWLing Post reader, Klaus Boecker, who originally posted these images of his homebrew magnetic loop antenna on the Shortwave Radio Station Listening Facebook page.

I love the design of his mag loop which easily allows for a vertical or horizontal orientation.  Kaus has discovered, in certain cases, places the loop in a horizontal position dramatically decreases the noise level.

Having a little fun with what I call “urban camouflage” Klaus recently decorated his antennas to match the neighborhood flower boxes!

I’m sure more than one neighbor may be wondering what sort of creative floral arrangement Klaus has planted! 

Klaus notes that the vertical to the left of the loop is a a 2m / 70cm J-Antenna.

Thank you again, Kalus, for allowing me to share your images here on the SWLing Post.  I imagine your modest home-grown antenna farm works some serious DX on occasion!

Thanks again for sharing!

Readers: Have you camouflaged or decorated your antenna(s)?  Please share your photos!

Guest Post: Backpack-Shack radio listening

Many thanks to SWLing Post contributor TomL, who shares the following guest post:

Illustration 1: Main contents

Backpack-Shack radio listening

by TomL

So, the Car Shack idea was good, but I felt constrained by lack of access to better locations to listen to shortwave radio. I took most of the original equipment and stuffed it into a photo backpack I was not using and now I have a portable listening station. Now I can listen in my car or in the field fairly easily.

LowePro350AW – The backpack has three main compartments, integrated carry handles, nice padded waist belt, and a couple of ways to stick a 3/4-inch PVC pipe into external tripod or water bottle pouches. My homemade 14-inch loop antenna with Wellbrook amplifier is light enough to be attached to a 3-foot PVC pipe attached to the backpack. The Palstar preselector (active antenna) and KIWA BCB filter are still part of the portable setup. I added a Daiwa two-position switch to cut out the KIWA BCB filter so I can listen to mediumwave. Power for all these devices are Powerex AA’s for the Sony 2010 and two 12V power packs made from three sets of XTAR 14500 lithium batteries + one dummy AA. I have mounted the electronics and wires using large cable tie-wraps to a 14×10 inch polypropylene kitchen cutting board (sturdy and easy to drill through).

Illustration 2: The electronics board fits neatly into the laptop section of the backpack

Illustration 3: Backpack Shack in operation

Here are some recordings from two test outings around 2100-2200 hours UTC. A local county park (“Forest Preserve”) purposely has few man-made structures (just a trail, picnic shelter made of wood and an outhouse). It is about 15 minutes drive from where I live; the reception is notably clear of local noise. There is an occasional wide-band noise that comes and goes but nothing else I can identify as detrimental noise and it is mostly just a nuisance.

Cuban Numbers station on 11635 kHz:

Click here to download.

VOA from Santa Maria di Galeria, Italy in French on 12075 kHz:

Click here to download.

All India Radio on 11670 kHz:

Click here to download.

BBC Ascension I. on 11810 kHz:

Click here to download.

R. Guinea with music and announcer on 9650 kHz:

Click here to download.

A big downside of the Forest Preserve, like most parks now, is that it is ONLY open from sunrise to sunset and strictly enforced. So, my personal quest for nighttime access to an RF-quiet location continues (I guess I will have to buy/build my own)! It begs for an even more portable setup than this one. That means buying an SDR (with control via a tablet), miniaturizing the antenna, and modifying the lithium power packs to fit in a very small backpack or fanny pack.

If I can miniaturize it enough, I will be able to use common parts of this setup at home, in the car, and at field locations for either mediumwave or shortwave listening. I could then pre-install the unique parts in those situations and just plug-and-play, so-to-speak!

It could be that the continuing tech wave of small, powerful, wide-band equipment is causing a revolution in general. A type of radio revival may be at hand where regional radio starts to take a foothold, catering to a multi-state area and not just to one local metro area – with its one-city mindset and control (Do I really care that the Big City is installing a downtown-only, 12 million dollar bike and jogging connection + hearing endless whining about how bankrupt pensions are putting that County at risk when I never go there and don’t care to?). Portable wide-band radios allow for hours of listening to various types of broadcasts!

An example could be to use digital broadcasts over longwave (somewhere from 150 kHz-500 kHz) which allows ground wave signals to travel hundreds of miles reliably during the day or night without depending on variable skywave propagation. Digital would enhance the listener experience in stereo. It would probably need a narrower type of digital modulation since the current “HD Radio” standard is really too wide and splatters everything at adjacent frequencies. Pure wishful thinking but the technology is available to make something NEW happen!!

Cheers from NoiZey Illinoiz,

Thank you, Tom! You certainly have the right idea: taking your radio to the field! Keep us informed about your progress and updates. No doubt, over time you will discover a year-round spot to play radio in the field!