Many thanks to SWLing Post contributor, Ron, who shares the following review of the PK Loop Mini (A-LOOP-MTAM):
Standard PK Loose-Coupled Loops (the “A” series) are 14 inches in diameter…they are
for use with a receiver having a built-in ferrite bar antenna.
Don’t think they’re not capable of serious DX…a few years ago a friend in Texas
snagged and recorded France Inter (162 kHz) on a 14 inch standard PK LW
loop using a Sony 7600GR.
But this is about the PK Mini 10 inch loop for Medium Wave (there are none for
The build quality is superb as with all PK loops. The band has two ranges: 525 to
710 and 710 to about 1720 kHz. Paul Karlstrand uses a unique design consisting
of flat computer cable and a custom made circuit board to connect the turns
The low end simply switches in a fixed capacitor across the variable to lower the
The Mini has 25% less sensitivity than the standard 14 inch loop according to the website.
Currently it can be had for $66 USD delivered to your door from Melbourne…this one
was ordered on a Monday and showed up a week later,which is outstanding considering
it had to clear customs in NYC.
Performance is virtually identical with the Tecsun or Terk loops, which are 9 inch loops.
So why buy a PK?
You get what you pay for, or not…the PK is fairly robust compared to the Tecsun or Terk.
It’s made to last and it’s a PK Loop.
Many thanks to SWLing Post contributor, Chris Freitas, who writes:
“I am thinking of the new RSP1A SDR. Would you know of a good indoor antenna that would work well with it?”
Your antenna question is simple, but the answer is complex!
First off, I think the RSP1A is a great choice as it’ll give you proper exposure to the world of SDR (1 kHz to 2 GHz!) at a modest price.
Unlike a portable radio of course, your SDR must be connected to a PC, laptop, tablet or some sort of mini computer like Raspberry Pi. This limits your ability to easily try different antenna locations within your home compared to, say, a battery-powered portable radio. It might take some dedicated experimentation and patience.
Indoor antennas are so vulnerable to the radio noise within your home.
If you live in an off-grid cabin with no radio interference nearby, even a simple $1 random wire antenna hooked up to RSP1A’s SMA connector would yield results. I occasionally spend my summers in an off-grid cabin and it’s simply amazing what you can do with a modest setup when there are no man-made radio noises around.
Listening to the final broadcast of Radio Netherlands in an off-grid cabin on Prince Edward Island in 2012.
But how many radio enthusiasts live in an off-grid cabin? Answer: very, very few! Most of us only get to experience off-grid life during natural disasters when the electrical grid has been damaged in our neighborhoods.
The reality of indoor antennas
You’ve told me previously that you live in an apartment in an urban setting, hence you probably cope with a lot of RFI.
When an antenna is indoors, it is forced to function within this RFI-dense environment. Your telescoping whip or wire antenna doesn’t discern between radio noise and your target broadcast signal. Thus, noise can overwhelm your receiver, essentially deafening it to all but the strongest shortwave broadcasters.
This is why if you had a means to put a small random wire antenna outside–even if it was simply draped outside a window–it would likely perform better than an indoor antenna. I’m guessing this isn’t an option for you, Chris.
A broadband loop antenna (image courtesy of wellbrook.uk.com)
While you can build an amplified mag loop antenna (like our buddy, TomL) it’s not a simple project. Passive single turn loop antennas, on the other hand, are quite easy to build but are narrow in bandwidth (here’s a very cheap, simple passive loop project). You would likely design a single passive loop to serve you on a specific brodcast band and would have to retune it as you make frequency changes. You could build a passive loop antenna for less than ten dollars if you can find a good variable capacitor. Here’s another tutorial.
Commercially produced amplified wideband magnetic loop antennas are not cheap, but they are effective. If you’re a serious SWL, a good mag loop antenna is worth the investment.
Here are a few of my favorites starting with the most portable:
W6LVP sells two versions of the antenna–since you’re not operating a transmitter, this $250 model would be all you need. indeed, if I were in your shoes, this would likely be the loop I purchase–very cost effective.
Wellbrook antennas are the staple magnetic loop antenna for many DXers.
Wellbrook makes a number of loops, but since you have no plans to mount this outside, I believe their indoor model would suffice.
Other loop options
There’s no shortage of magnetic loop antennas on the market, but most are pricer than the models I mention above and I know you have a tight budget. Here’s are some models we’ve mentioned on the SWLing Post in the past:
I hope this helps, Chris! This post is by no means comprehensive, so I hope others will chime in and comment with their experiences. Good luck fighting urban noise and I hope you enjoy your journey into the world of the SDR!
SWling Post contributor, Ron, recently noted that Jay Allen reviewed one of Paul’s inductively-coupled mediumwave magnetic loop antennas. Jay gave it good marks on performance as it compares favorably with the Grundig AN-200, Select-A-Tenna M, and Terk Advantage AM–even having a performance edge due to it’s larger loop diameter. (Note that Paul makes a number of loop sizes–click here to download PDF of catalog.)
In Canada last summer, I used the PK Loop on a number of field radio listening sessions.
But what really sets the PK Loop apart from its competitors is its durability. PK’s Loops are built to be incredibly rugged. I routinely throw my PK Loop antenna in bags/packs and–unlike most of my other radio components–never worry about how it’s padded or protected. There’s little to damage unless you’re intentionally abusive to this antenna. My Grundig AN-200 antenna, on the other extreme, has exposed coated wires around its loop that I’m constantly concerned about harming in transit.
Ron’s message reminded me that I never followed up after posting a preliminary review of the PK Loop C-LOOP-HDSW6-18 in 2016.
Shortly after publishing the review, I had a fantastic opportunity to evaluate how well the PK Loop would perform in a typical hotel room. My buddies Eric (WD8RIF), Miles (KD8KNC) and I stayed overnight in a hotel on Wright-Patterson Air Force Base during our mini National Parks On The Air DXpedition.
My Elecraft KX2 connected to an external random wire antenna.
The hotel room was indeed dense with RFI.
We hooked my Electraft KX2 to both the PK Loop and to a simple random wire antenna.
Without a doubt, the PK Loop was much better at mitigating radio noise than the wire antenna we hung on the inside of the hotel window.
Unlike most modern hotels, however, this one actually had operable windows, so we tossed the random wire out the window and made another comparison. In this case, the external wire antenna consistently outperformed the PK Loop, no doubt because it had the advantage of being outside the radio noise cloud within the hotel’s walls. It goes to show that outdoor antennas–even if simply hanging from a room window–will almost always outperform comparable indoor antennas.
A late evening listening session on the condo balcony.
Last summer, I also spent two months in a condo near Québec City. The condo was dense with RFI–the PK Loop made the experience much more bearable. The loop couldn’t completely eliminate all of the persistent wideband noise, of course, but it did reduce noise to a level that I could enjoy some of my favorites like RRI, VOG, VOT, REE, WRMI, RNZI and even weaker stations in North America like the BBC and DW.
Even the shortwave version of the PK Loop can null out QRM to some degree by rotating the loop perpendicular to noise. I became quite adept at this by the end of our stay.
Since I purchased the PK Loop, it’s been a constant travel companion and I highly recommend it. I don’t believe you’ll find a more durable or effective portable mag loop antenna on the market.
PK Loops are built by Paul Karlstrand in Australia who has a stellar reputation with his customers. For those of us living outside Australia, there will be additional shipping costs, but they’re negligible and Paul has been exporting these loops for many, many years. I believe I received my loop within a couple of weeks of ordering it.
Since I purchased the Elecraft KX2 last year, I find I do almost as much SWLing with it as I do ham radio activity. The KX2 is actually a brilliant shortwave broadcast receiver–check out these audio samples. It’s incredibly sensitive, selective and outperforms all of my portables. It’s also a joy to operate, once you learn your way around the controls.
I’ve been at the South Carolina coast all week on an active family vacation. What little time I’ve had to play radio, I’ve used the KX2/PK Loop combo.
I can set up the KX2 and PK Loop on a small table or foot stool with room to spare. I typically use a pair of headphones with the KX2 since its built-in speaker leaves much to be desired (but is better than the KX3’s internal speaker, in my opinion). With headphones, you can also take advantage of the “delay” audio effect which makes broadcasts sound much wider that the 5 kHz maximum bandwidth.
Another favorite travel receiver is the CommRadio CR-1a. Like the KX2, it’s compact, has a built-in battery and (unlike the KX2) can even be charged from a standard USB source.
I still manage to take the KX2 on travels more often than the CR-1a simply because I always have the option to put on my ham radio hat and do field/portable operation should I choose.
But CommRadio is cooking up a new radio: I’m watching the new CommRadio CTX-10 with interest since it might also serve both of these radio purposes!
The CommRadio CTX-10 QRP transceiver
I will review the CTX-10 when it’s on the market.
On a side note: since I own both the KX2 and KX3, I’m planning to purchase the KXPA100 100 watt amplifier for the shack next year. At $749 for the ATU-less kit version, it’s a hefty sum–indeed–enough to purchase another 100 watt transceiver like the Icom IC-7200. But in the end, I’m so please with both radios I think it’s worth the investment. Thankfully, the KXPA100 was not included in the Elecraft Black Friday sale. I did not need that temptation.
Post readers: Any others take a compact general coverage transceiver on travels? What model do you prefer? Please comment!
A Sony SW100, a PK Loop, and a pint of L’Écurieux brown ale. Lovely trio!
If you’re a regular Post reader, you’re probably aware that I enjoy a relatively RFI-free environment at my rural mountain home. RFI-free living is something of a luxury, even though our rural location also equates to appallingly slow Internet service.
But unfortunately, when I travel, I usually find that I’ve traded my RFI-free atmosphere for the chaos of noise-ridden bands. If you’ve ever stayed at a modern hotel and tried to tune to anything on mediumwave or shortwave, you’ll know just what I mean.
We’ve spent this summer, like last, near Québec City, Canada. Near this fairly large city, I’ve been greeted by more than enough RFI to make up for the lack of RFI most of the year.
I attribute the atrocious RFI to the number of light dimmers the developers put in this condo complex and the proximity to a field of noisy electrical poles. Of course, all of the unregulated power supplies in the area don’t help, either. It’s a jungle of noise.
While the PK Loop seems to pair well with my Sony SW100, I also love using it with my Elecraft KX2 for SWLing.
Sadly, the PK Loop doesn’t provide the noise mitigation of a large wideband mag loop antenna–like a Wellbrook or Pixel Loop–but it does lend itself to excellent portability and takes the edge off the noise.
While it’s easy to do my radio listening in the condo from a comfy chair, in reality, it limits what I can receive in a serious way. The 31 meter band, for example, is so heavily submerged in RFI that only the strongest stations can punch through (for example, Voice of Greece, Radio Romania International, WRMI, WBCQ, Radio Havana Cuba, China Radio International).
So, what can I do?
Hit the field, of course!
That’s right. Taking a page from the books of SWLing Post contributors London Shortwave and Clint Gouveia, I realize I can simply leave the RFI behind and seek a sound, radio quiet spot for SWLing/DXing!
My listening post last year–during the BBC Midwinter broadcast–in the parking lot of St-Anne-de-Beaupré basilica.
Over the past two months, I’ve taken time to escape the RFI and do a few live listening sessions and spectrum recordings in the field. I’ve always got my SDRplay RSP, Elecraft KX2, and Sony ICG-SW100 at the ready. In terms of wire antennas, I’ve deployed my NASA PA30 and even my QRP Trail-Friendly EFT, with good results.
Listening to the 2017 BBC Antarctic Midwinter Broadcast from the back of my vehicle in Saint-Anne-de-Beaupré, Québec, Canada.
Just a friendly reminder that if you live in an RFI-dense environment, you can certainly design a system to help mitigate RFI at home. After all, home is where you likely spend the bulk of your free time.
View of the Saint Lawrence River from my back-of-the-minivan listening post.
But, again, the easiest way to substantially increase your chances of snagging DX stations is to simply hit the field.
Join me in giving it a try. Find an RFI-free location with access to a couple of trees to hang a simple wire antenna–say, in a park, at the side of a rural road, on a friend’s farm…and if you find the listening good, make it your radio get-away. You’ll likely find that your portable shortwave radio can outperform your at-home tabletop receiver simply by removing yourself and your radio from the noisy environ of indoors.
When you first start doing radio in the field, it might feel a bit awkward–especially if you’re taking more than a portable shortwave along for the ride–but you’ll soon enjoy the fresh air ambiance and maybe even prefer it to indoors. Even if you’re in a public setting where curious passers-by may want to know what you’re doing, as they undoubtedly will…When questions arise, take a (brief!) moment to educate your questioner(s) about the fascinating and nearly-forgotten world of shortwave radio––maybe you’ll inspire others to listen in, too.
And trust me: once you’ve been to the field a few times, you’ll start to look forward to playing radio in the great–and noise-free–outdoors!
Over the past year, a number of SWLing Post readers have asked me to review the PK Loop portable magnetic loop antenna produced by Paul Karlstrand in Australia.
I finally caved in and purchased one.
I ordered the shortwave version of the loop, the C-LOOP-HDSW6-18 in early November and received it about one week later.
The Sony SW100 tuned to WBCQ.
I was first introduced to this antenna by SWLing Post contributor, Mark Fahey, who brought it to the SWL Fest and our 2015 PARI DXpedition.
Mark has taken his PK Loops (both the shortwave and mediumwave models) on his numerous travels around the world. He finds that they’re relatively effective portable antennas in RFI-dense environments like hotels and guest houses. They’re better at mitigating RFI than, say, portable wire antennas or telescopic whips.
Mark hooks up his portable SDR to the PK Loop and makes spectrum recordings (wideband recordings)–from, say, his hotel room in Kuala Lumpur–then takes the recording back home to listen and tune at his leisure via his laptop or tablet PC. While I’ve certainly made spectrum recordings while travelling in the past, the appeal of such a portable loop antenna is what finally caused me to pull the trigger.
The PK Loop is a small loop antenna–measuring about 12″ in diameter. It’s encased in UV-stabilized PVC conduit and the matching box also seems to be made of PVC. It feels very durable and can, no doubt, even survive the wildest of luggage handling.
The PK Loop has an attached battery 9V battery holder, but can actually be powered by any 9-18 volt DC supply. Current consumption is less than 15 mA. On the matching box, you’ll find a tuning knob, a BNC connector, DC power in port and a HI/LOW gain switch. My loop shipped with a 2 meter BNC-BNC Cable, 3.5mm adapter, and DC Power lead to open ends.
Operating the loop is very simple:
Power the antenna with a 9V battery or other DC source
Chose either the high or low gain setting
Place it on a stable surface (height from the ground is not a critical issue, but you should avoid placing it next to noisy electronics or mobile phones)
Connect the PK Loop to your receiver’s antenna jack with the supplied cable
Turn on your receiver to the desired meter band, then adjust the loop’s tuning knob until you hear the signal level peak
Start listening, keeping in mind that as you tune around the band you may need to adjust the loop’s tuning knob for maximum gain
Loop antennas, in general, are fairly narrow-band and–unlike a Wellbrook or Pixel Loop–manual adjustments need to be made with the tuning knob to match the PK Loop as you scan across bands.
Still, I see why Mark favors the PK Loop for spectrum recordings: the bandwidth is wide enough that if I tune the loop to the middle of the 31 meter band, for example, it does a fine job covering the entire band.
On the air
My free time has been very limited since receiving the PK Loop earlier this month, but over Thanksgiving holiday, I took it to my family’s home that has relatively high RFI levels.
The following are a couple of videos I made with my Moto X smartphone. I’ll be the first to admit that these are not the best videos–I had no tripod and the Moto’s microphone leaves much to be desired–but I think you’ll still get the idea of how well the PK Loop works.
So far, I’m very pleased with the PK Loop. It does seem to mitigate noise better than other portable antennas I’ve used in the past and certainly improves my SW100’s reception. It makes SWLing with the Elecraft KX2 or KX3 easy and convenient.
One word of caution: if you use the PK Loop with a transceiver like the KX2, please turn off the ATU, and set the power level to 0W before using. The PK Loop is receive-only and will not handle any RF power.
Note that with the SW100, I have only used the PK Loop’s low gain setting. I’m a little nervous about overloading the SW100, so do not plan to use the high gain setting. The Elecraft KX2 seems happy to handle either gain setting: I imagine this will be the case with most general coverage transceivers and tabletop receivers.
More to come!
In a couple of weeks, I’ll be staying in a hotel room (likely with inoperable windows and heavy RFI) so I will attempt to put the loop through its paces and compare it with my radio’s built-in antenna. Stay tuned!