Tag Archives: Magnetic Loop Antennas

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!

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Michael pairs the Tecsun PL-990 and the AOR LA400

Many thanks to SWLing Post contributor, Michael Ye (BD4AAQ), for the following guest post:


In the Loop: PL-990 and LA400, a Perfect Match

by Michael Ye (BD4AAQ)

PL-990 and LA400

I have been a happy owner of Tecsun’s PL-880 world band receivers for years. In fact I have two PL-880 radios, one sitting at home and the other staying in my car. So, after Tecsun introduced the new model PL-990 in late 2020, it didn’t take me long to decide to purchase one. In this article I will discuss the Tecsun PL-990 receiver working with loop antennas, while referencing some relevant features of the PL-880.

Overall performance of the PL-990

Merely by its model number, it is easy to regard the PL-990 as an upgraded version of the already highly reputable PL-880. As expected, the PL-990 can very much be regarded as a combination of all the existing fine radio features of the PL-880 AND the music and bluetooth additions, with a number of improvements for instance in shortwave and medium wave performance. The ergonomic design of the PL-990 looks and feels different from that of the PL-880 in a number of ways. Although I may prefer the the more slim and elegant appearance of the PL-880, the PL-990 gives a more rugged and durable feeling, among other improvements over the older PL-880.

Working with loop antennas

The PL-990 and the PL-880 side by side

Living on the twelfth floor of a condominium in the crowded Shanghai, I have often been fascinated with loop antennas. As a licensed amateur operator, I have used the MFJ-1786X and have been impressed with its performance. On reception, I also find loop antennas appealing, as they are able to pull in weak signals while noticeably reducing electro-magnetic interference rampant in the urban environment. I have an unbranded shortwave loop antenna which I believe is based on and performs similarly with the AOR LA320. Despite its excellent performance, it is only good for the 5MHz – 15MHz shortwave range. So a few years ago when AOR launched the new LA400 wideband loop antenna, I bought one, which I often pair up with the PL-880 and other radios for shortwave listening, and get satisfactory results!

Antenna Switch on the PL-990

Now, back to the PL-990. When I first tried the PL-990 with the LA400, the results were generally good but not as good as as compared with using the same LA400 on my PL-880. This puzzled me for a day or so until I realised that the PL-990 actually has an antenna switch which the PL-880 does not have. The switch is used to toggle between an internal antenna (i.e. the built-in ferrite bar/telescopic antenna) and an external one (e.g. the AOR LA400). So a new PL-990 user who has often operated the PL-880 when first using the PL-990 could easily ignore the switch which should be pushed to “Ext” when plugging in an external antenna. This explains why the PL-990 may suddenly appear less sensitive than expected.

“Ext” antenna input for all bands

Contrary to the PL-880 whose external antenna socket is only good for shortwave signal input, the PL-990’s external antenna socket works with all bands, from long wave to FM. I found this to be an important and very useful change, and a pleasant surprise for my LA400, which covers a wide range of frequencies from long wave to medium wave to FM and up to 500MHz.

Once the LA400 is connected, the correct band selected, and last but not least the antenna switch turned to “Ext”, the PL-990 and the LA400 work like a charm in the indoor setting, remarkably better than the built-in telescopic antenna. With the loop connected, while there is not much to expect on the long wave band because of very few long wave stations remaining in the world, reception improves considerably on all other bands including on the medium wave and FM bands, as is also reflected on the upper right hand display of the signal strength and S/N ratio readings. Needless to say, performance on shortwave is as good as on the PL-880, if not better (again, remember to push the antenna switch to “Ext” when using it on the PL-990). Using the AOR loop on the PL-990 for FM reception is somewhat different as there does not seem to be a noticeable tuning point. Simply select the “Others” band, which appears to be broad enough for fair FM reception.

Tecsun AN-200 loop antenna

It is worth mentioning that I have a Tecsun AN-200 tunable medium wave antenna, which I have not used often. As its name suggests, it is for medium wave reception only. I tried it on the PL-990. Works great.

The AN-200 and the PL-990

It is hard to tell which one, the PL-LA400 or the AN-200, fares better, as the signal strength and S/M readings are quite close. They both perform better than the radio’s internal ferrite bar antenna to varying degrees, by improving the signal strength or the S/N ratio or both. The Tecsun loop is a passive antenna, meaning no power is required, making it easy to be used “wirelessly”, by simply placing the loop close to the radio, without having to be connected to the radio via a cable.

Chocolate, our house cat, tries to enhance reception with her tail

It should be noted that in the “wireless” mode of the AN-200 the antenna switch on the PL-990 should remain at “Int” so as for its built-in ferrite bar and the loop to couple with each other.

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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!

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Guest Post: KK5JY’s Porch Loop Receiving Antenna

Can you spot the antenna in this photo?

Many thanks to Matt Roberts (KK5JY) who has kindly given me permission to re-post the following article he recently published on his website KK5JY.net. Many thanks to SWLing Post contributor, Grayhat, for the tip!

 Note: The Porch Loop project below is a re-configured Small Receiving Loop (SRL) antenna. For SRL construction details, check out Matt’s primer.


The Porch Loop

by Matt Roberts (KK5JY)

The small receiving loop, or SRL, is a versatile, effective, and very space-efficient receive-optimized antenna for the HF bands.  They are easy to build, and can be made very inexpensively.  Most typical designs use symmetric shapes, like circles, diamonds, octagons, etc., and are mounted on some kind of mast.  This makes it easy(-ier) to install the antenna clear of nearby metal and electronics.  It also makes the antenna rotatable, so that the nulls can be pointed at RFI sources.

These aren’t the only options for the SRL, however.  These little loops can be made to fit in just about any available space.  In fact:

  • They are effective at any reasonable installation height, including very close to the ground.  The installation height doesn’t change the pattern shape, only the pattern strength.
  • They can be made nearly any shape.  The shape does not have to be symmetric about any axis or combination of axes.
  • They can be fed at just about any point on the loop.  A typical feed location is bottom-center, but off-center feeding has negligible effect on the pattern shape.
  • The wire can be bent out-of-plane; in other words, the loop doesn’t have to be “flat.”

There are a couple of requirements for obtaining predictable performance, however.  First, the antenna does need to be an electrical loop.  That is, it is a single wire connected between the conductors of the feedline, forming a complete circuit.  Also, the circumference of the loop wire should be electrically small (i.e., significantly less than ? / 4) on the bands where it is to be used.

Figure 1. The antenna location (click to enlarge)

As a personal challenge, I recently installed such a loop on my front porch.  Everything about this installation defies conventional wisdom — it was installed very close to the ground, it was an irregular shape, it was fed off-center, and the wire was wound in and around an irregular support structure, rather having all the wire in a single plane.

And the resulting antenna still performed very well.

Figure 2: Antenna Location Outlined in Red (click to enlarge)

The loop is essentially the same device as the one in the original SRL article.  See that article for more construction details.  This version is simply stretched and twisted to make it fit the space and supports available.  The wire was woven around the boards in the porch’s deck rail, and fed off to one side, so that the transformer housing could be “hidden” behind the trash cans.

Figure 3: Feedpoint Transformer (click to enlarge)

The wire was insulated with an off-white THHN, which made it blend in with the color of the trim of the house.

Figure 4: 40m Reception 10h Overnight (click to enlarge)

Even with its suboptimal installation details, the overnight 40m DX spots were numerous and well-distributed, as seen in Figure 4.  There were DX spots at nearly 10,000 miles, there were NVIS spots, and there were countless at all distances in between.  So the antenna was just as effective as its more ideally shaped brethren, despite it’s unconventional installation details.

Other ideas for possible locations of such a device could include:

  • In an attic.  The antenna could be nailed to a vertical panel, or strung like a spider’s web inside the frame of a truss or other open area.
  • Under a tree.  Taking another idea from the spiders, the antenna could be hung and pulled into shape using light guys or tree branches.
  • On a wooden fence.  If you have a wooden fence, the antenna could be installed against the fence panels.  This option could allow a wide range of circumference lengths.
  • Attached to an interior wall of an apartment.  The shape could be chosen to keep the loop clear of in-wall wiring, to help preserve its performance.

The original mast-mounted SRL antennas still have some advantages.  Perhaps the biggest advantage is that they can be easily rotated to null out a nearby strong noise source.  That said, if you are looking for an antenna with better receive performance than a large resonant vertical, the SRL can be stretched and squeezed into service just about anywhere.


Many thanks for sharing this project, Matt!  So many of our readers live in situations where they are forced to use stealthy and compromised antennas. What I love about your porch loop is that even though it breaks several loop antennas “rules,” it’s still amazingly effective. 

I encourage SWLing Post readers to check out Matt’s website as he has written articles covering a number of interesting radio and antenna projects.

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DIY: How to build a Passive Resonant Transformer-Coupled Loop Antenna for HF reception

We recently posted a tutorial on building a simple Noise-Cancelling Passive Loop (NCPL) antenna. This prompted SWLing Post contributor, Bob Colegrove, to share his excellent article on building a Passive, Resonant, Transformer-Coupled Loop (PRTCL) Antenna:


A Passive, Resonant, Transformer-Coupled Loop Antenna for Shortwave

By Bob Colegrove

Over the years I have resisted the level-of-effort necessary to construct and maintain outdoor antennas.  Rather, I have focused on squeezing out all of the microvolts I could get inside the house. Many years ago I had access to a well-stocked engineering library, and used my advantage to gather information about the theory and development of loop antennas – a daunting undertaking for an English major.  Ultimately, by adhering to a few basic rules, some of them dating back 100 years, I found quite acceptable performance can be had with an indoor passive antenna intersecting just a few square feet of electromagnetic energy.

Theory

There are a couple of advantages of resonant loops as opposed to non-resonant ones.  The first is the fact that the signal dramatically increases when you reach the point of resonance.  The second follows from the first in that resonance provides a natural bandpass which suppresses higher and lower frequencies.  This gives the receiver a head start reducing intermodulation or other spurious responses. The downside of all this is that the resonant loop is, by design, a narrow-band antenna, which must be retuned every time the receiver frequency is changed by a few kHz.  On the other hand, there is nothing quite as rewarding as the sight (S-meter) and sound you get when you peak up one of these antennas – you know when you are tuned in.

There is nothing new about the loop antenna described here.  It’s just the distillation of the information I was able to collect and apply.  There are a number of recurring points throughout the literature, one of which is the equation for “effective height” of a loop antenna.  It basically comes down to the “NA product,” where N is the number of turns in the loop and A is the area they bound. In other words, provide the coil with as much inductance as possible.  Unfortunately, for resonant loops, the maximum coil size diminishes with frequency.

With this limitation on inductance, the challenge becomes minimizing unusable capacitance in the resonant frequency formula in order to get the highest inductance-to-capacitance (L/C) ratio possible.  Some of the unusable capacitance is built into the coil itself in the form of distributed capacitance, or self-capacitance between the coil turns. This cannot be totally eliminated, but can be minimized by winding the coil as a flat spiral rather than a solenoid, and keeping the turns well separated.

The second trick is with the variable capacitor.  Even with the plates fully open, there is residual capacitance on the order of 10 to 20 picofarads which can’t be used for tuning purposes.  A simple solution is to insert a capacitor in series, about ¼ the maximum value of the variable capacitor. This effectively decreases the minimum capacity and extends the upper frequency range.  In order to restore the full operating range of the variable capacitor, the fixed capacitor can be bypassed with a ‘band switch.’ With the series capacitor shorted, the variable capacitor operates at its normal range and extends coverage to the lower frequencies.

Construction

I have constructed similar loops covering long wave, medium wave, and shortwave all the way up to about 23 MHz.  I wanted to optimize this loop for the most active portion of the shortwave spectrum. Consequently, it covers approximately 2.6 to 12.3 MHz.  See Figure 1.

Figure 1.  A Passive, Resonant, Transformer-Coupled Loop Antenna for Shortwave

Figure 2 is a schematic diagram of the antenna.  Cd (in red) is the distributed capacitance of the primary coil, L1.  This is not tunable capacitance, but it still contributes to the resonance; likewise, the 15 pf minimum capacitance of C1.  By adding C2, the minimum total capacitance can be lowered to greatly increase the upper range of the antenna. S1 is the ‘band switch.’  It shorts out the series capacitor, restoring the maximum low frequency.

Figure 2.  Schematic Diagram

Frame – The frame is made from 3/8”-square basswood or poplar dowel (see Specialized Parts).  Two pieces, each 36” long, have been predrilled at ½” intervals to accommodate the primary and secondary coil wire (think of a tennis racket).  It is a good idea to drill holes along the length of each dowel – more than you will need. You may decide to change things later on, and drilling holes in an assembled antenna is not easy.  Also the two dowels are notched in their centers to fit together. See Figure 3 and Figure 4. The clear plastic disk in Figure 4 is a packing disk from a spindle of CDs; it is cemented to the square dowels, and used to hold them at right angles.  Any rigid, light-weight material will do.

Figure 3. Square Dowel Showing 1?2” Hole Spacing and Lacing of Secondary Coil


Figure 4. Cross Members Notched and Square Dowel Reinforcement

Primary Coil – With a coil size 36” in diameter, you likely won’t be able to get more than two turns of wire to resonate at frequencies up to 12 MHz.  This takes into account the precautions described above to minimize unusable capacitance.  AWG 22 stranded, insulated wire was used to lace this coil; ensure the dowels remain at right angles with one another.  Note that one set of holes in the dowel is skipped between the first and second turn.

Tuning Capacitor – Almost any salvaged variable capacitor can be made to work.  For a typical 2-gang unit, the gangs can be connected in series through the common rotor sections and metal frame with the stator terminals of each gang used as the outer terminals.  This will create a lower minimum capacitance as described above.

For the antenna described here, a single-gang, 365-pf capacitor (see Specialized Parts) was used with a fixed mica capacitor in series.  The minimum capacitance of the variable capacitor is nominally 15 pf. Figure 5 shows the capacitor assembly for the primary circuit. Components are mounted on a perforated circuit board, which, in turn, is mounted to the bottom of the vertical square dowel.  A portion of the base can be seen at the rear. A large diameter tuning knob is suggested, as the peak tuning for a properly constructed loop will be very sharp and require a delicate touch. As an option, I have used a planetary reduction mechanism on other antennas to give an 8:1 ratio with the capacitor shaft.

You may notice at high frequencies that the antenna is somewhat unstable with body contact of the knob or around the tuning capacitor.  This is because the resonant circuit is operating at a very high L/C ratio with capacitance at just a few picofarads. Body capacitance will tend to detune the antenna.  It may be useful to extend the knob 2 or 3 inches from the tuning capacitor with an insulated shaft.

Figure 5.  Capacitor Assembly

Secondary Coil – The secondary coil operates at low impedance to feed the lead-in.  There are two extremes governing the size of the secondary coil. A coil which is too small will not pick up much of the magnetic field generated by the primary circuit at resonance.  On the other hand, a secondary coil which is too large will overcouple or load the primary circuit. This will reduce the Q, or sharpness of the tuning.

The secondary coil is 16” diagonal at the largest turn and consists of 7 turns of AWG 20 buss wire.  Buss wire was used so the coil can easily be tapped after the 1st, 2nd, 3rd, 4th, and 6th turn.  The 7th turn is not currently used.  A tapped coil will provide better impedance matches to the lead-in when the antenna is used through a wide frequency range.  The taps are selected with a rotary switch. The taps are connected so that the outer turns are used first, and inner turns connected as needed.  It is important that unused turns remain unconnected (free) rather than shorted. See Figure 6.

Figure 6.  Secondary Coil Switch

Lead-in – A twisted pair of AWG 22 stranded wire is used as the lead-in.  This will be more flexible than coax. The lead-in should be kept as short as possible and twisted tightly so it will not pick up any signal by itself.  This is important at shortwave frequencies. A twisted pair can be fabricated from two lengths of wire with one set of ends anchored in a vise, while the remaining ends are twisted in the chuck of a hand drill.  Most portable radios are equipped with a standard 1/8” phone jack at the external antenna connection point.  So, this antenna is terminated with a 1/8” phone plug.

Base – There is nothing special about the base.  Your only guidance should be to make it as stable as possible.  Since the frame is light, most of the weight will be at the bottom with the capacitor assembly and other parts.  That helps stability. This antenna uses a 5” plastic jar lid for the bottom. Keep the base small, as the antenna will likely be operated on a desk or table.

Operation

The antenna is intended to operate in close proximity to the radio, such as on a desk or table.  There must be sufficient space to rotate the loop laterally. As described, this antenna has a range of 2.6 MHz through 12.3 MHz with a band overlap around 8 MHz.  Depending on your selection of capacitors, your range and overlap may be slightly different.

  1. Tune the receiver to a desired frequency.
  2. Set the band switch on the antenna to the corresponding band.
  3. Tune the antenna capacitor to resonance (peak signal).
  4. Rotate the secondary switch to the position of maximum signal strength.  Begin with the fewest turns (generally one) in the secondary.
  5. It may be necessary to repeak the primary circuit.

Repeat the procedure to test operation of the upper or lower band.

Unlike similar loops for long and medium wave reception, this antenna is not especially responsive to direction for peak or null signal reception.  However, you will find it very useful to reduce or possibly eliminate locally produced noise. Simply rotate the antenna on its base.

Modification

The basic concept for this antenna can easily be extended to higher or lower frequencies.  Removal of the inner turn of the primary will significantly raise the upper frequency; whereas, adding turns will increase the lower range.  Note that the lacing of the primary coil skips one set of holes in the square dowels between the first and second turn. This minimizes distributed capacitance between turns.  This separation should be maintained if additional turns are added to lower the operational frequency.

Specialized Parts

Some sources for square wood dowel and single-gang 365 pf variable capacitors are listed below.  The author does not endorse any of them. Prices for similar capacitors vary widely.

Square wood dowel:

Variable capacitor (365 pf):


Bob, thank you so much for sharing this excellent, detailed tutorial. Although I don’t have the exact same variable capacitor, I have all of the other components to make this antenna. I will have to put this on my Social DX bucket list! Thank you again!


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Beating the Quarantine Blues: Readers build homebrew NCPL antennas

My homebrew version of the NCPL antenna.

Recently, I published a step-by-step guide on building a Noise-Cancelling Passive Loop (NCPL) antenna. Evidently, this antenna project really resonated with readers! [See what I did there? If so, my apologies!]

I think this passive loop antenna project has been so appealing because (1.) most of us around the world are sheltering at home due to the Covid-19 pandemic and (2.) this project is simple and you likely have all of the components in your tool shed or junk box at this very moment.

A number you have written to tell me about your antenna builds and some of you have agreed to allow me to share your projects with the SWLing Post community.

Below, you’ll find three fine homebrew examples of the NCPL antenna–all of which were made with what these fine radio enthusiasts had on-hand:

Jerome van der Linden

Jerome’s NCPL antenna

Jerome writes:

Hello Thomas,

Well, I took up the challenge and built a NCPL antenna pretty close to your instructions.

Unfortunately, the coax I had available used (had aluminium shielding, and too late into the project I discovered solder would not take to it. My solution was to cannibalize a coax cable joiner (see photos attached), where – normally – the centre conductors are joined / held by a plastic centre piece and screw fittings.

The braid / shield for the two bits of coax is clamped / squeezed by an outer metal piece. My cannibalising effort involved removing the plastic centre bit which joins the two centre cores, and keeping just the outer metal component which I used (after completely cutting through the coax) to clamp the two metal braid sections, while the two centre copper bits were far enough apart for me to solder the leads for the ferrite balun.

Of course, I could not do the same at the top of the loop where the internal and external conductors need to swap over. I soldered some quite thick copper wire (perhaps 2mm in diameter) to each center core, pushed the center core into the opposing coax and coiled the 2mm thick copper tightly around each end of the coax.

Once it was all taped up it looks no worse than yours, and it does indeed WORK! [see photo above]

Here in Oz, I could not source the identical ferrite, but I think it’s pretty close. Best performance for me is on 11MHz, where the Radio New Zealand signal on 11725 is markedly better using the loop than the internal whip on my Tecsun PL-880. Other bands not quite so significant, but the Noise level is definitely lower.

As you say, Jerome, once all packaged up, it looks great! Sure, the mixture of materials you had on hand wasn’t ideal (aluminium shielding, etc.) but you found a way to make it work from the resources you had in your home. And I love the fact it’s lowed your RFI level!  Thanks for sharing!

Giuseppe Morlè (IZ0GZW)

Dear Thomas,

I’m Giuseppe Morlè (IZ0GZW), from Formia, central Italy, on the Tyrrhenian Sea.

I wanted to build your noise canceling loop seen on SWLing Post …
seems to work well especially from 40 meters. upward…
the diameter is 50 cm.
I will do other tests soon.
You can see the initial test on my YouTube channel via this link:

Thanks for the nice idea and a greetings from Italy.
73. Giuseppe IZ0GZW

Thank you, Giuseppe! What an amazing view you have there from your balcony! I’m quite impressed your PL-660 can take advantage of this design so well. We look forward to your other tests! Grazie mille!

John Mills

Hi Thomas,

My idea was to use a fitness hoop 75cm diameter bought off eBay. I removed the flashy striping to reveal a plastic like hoop that was joined in one spot with a plastic insert.

I have wrapped the whole hoop in tin-clad copper foil tape that has a conductive adhesive backing, but to be sure I have soldered all the overlapping seams. I drilled two holes opposite each other for the upper foil connections and the lower exit to the Balun.

Hopefully the three pictures will be helpful, I did the 4 turn design on Airspys website and it works really well connected to my RSPdx.

73

John

Thank you, John. What a fantastic way to build the NCPL antenna without using a coax for the loop. Indeed, since your plastic hoop has a small insert in the middle, you’ve an ideal spot to make the shield to center conductor cross-over.  Very clever! I also like how you mounted the 1:1 Balun (or Unun) on a small board. Thanks for sharing this.

Got Loops?

Post readers: If you have your own unique NCPL antenna design, please consider sharing it with us! Contact me with details and photos. I’ll plan to publish at least one more post with examples here in the near future.


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New Product: K-180WLA Active Loop Antenna with rechargeable battery

Many thanks to SWLing Post contributor, crvee8, who shares a link to the K-180WLA, a new active mag loop antenna.

Based on the product description, the K-180WLA sounds a lot like a typical magnetic loop antenna (and resembles the popular MLA-30), but what makes it unique is the fact that it can be recharged via a Micro USB port.

This means, there’s no need for a separate power supply.

There’s no mention of how long a charged battery would power the amplifier, but I imagine it would be respectable given it employs the 3.7V 18650 lithium cell.

The frequency range is 0.1-180 MHz and the manufacturer claims it, “provides a gain of about 20 dB, even when working to 450MHz gain, there is still about 8.9 dB.”

Battery power would certainly make this a very portable active antenna loop option. The price is right, too, at $55.88 USD which includes shipping from China. The listing claims only 5 units are available at time of posting.

Click here to view on eBay (partner link).

Post readers: Please comment if you’ve purchased this antenna. We’d love to hear your thoughts/review.

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