Category Archives: Portable Radio

The AirSpy HF+ Discovery and a new era of portable SDR DXing

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The following article first appeared in the January 2020 issue of The Spectrum Monitor magazine.

The AirSpy HF+ Discovery and a new era of portable DXing

I admit it: I used to be a bit of an old-fashioned radio curmudgeon. One of those, “I like my radios with knobs and buttons” likely followed by, “…and no other way!”

However, about fifteen years ago, many of my DXing friends started turning to the world of software defined radios (or in common parlance, “SDRs”). I staunchly opposed ever following in their footsteps. One of the reasons I for this––a good one––is that, since I spend the bulk of my day in front of a computer, why would I ever want to use a computer when I’m playing radio?

But then…gradually, I found myself playing around with a few SDRs. And I quickly learned that third-generation SDRs were capable of doing something very impressive (and fun), indeed:  making spectrum recordings.  Using this tool, I found I could record not only the audio of one individual signal, but the audio of entire swathes of radio spectrum.  And even more impressive, I learned that you could later load or “play back” the spectrum recording and tune through the bands as if in real time. Any time you want. Before long, I was hooked: SDRs had become my portal into radio time travel!

I quickly found that I loved many of the other advantages of using an SDR, as well, including visual ones––like the ability to view spectrum. The interactive interface allows one to actually see radio signals across the band in real time. I also found incredible value in waterfall displays, which show signals changing in amplitude and frequency over time. Cool stuff.

I purchased my first dedicated SDR in 2012, a WinRadio Excalibur. It was––and still is––a benchmark receiver, performing circles around my tabletop receivers and general coverage transceivers.

And today, although I own and love a number of legacy radios and still listen to them in the good old-fashioned manner to which I became accustomed, I find I’m now spending the bulk of my time DXing with SDRs.

And then, more recently, two amazing things happened in the world of SDRs. Strong market competition, together with serious innovations, have come into play. Thus, for less than $200 US, you can now purchase an SDR that would have easily cost $1,000 US only ten years ago. And now, in many cases, the $200 SDR of today will outperform the $1,000 SDR of yesteryear. We are, indeed, living in good times.

And now––no more a radio curmudgeon––I’m comfortable with my SDR-user status and time at the computer, and glad I was just curious enough about SDRs to let them into my radio (and computer) world.

Portable SDRs

Since I initially dived into the world of SDRs, I’ve tried to think of a way to take them into the field.

But first, let’s get an obvious question out of the way:

Why would you want to drag an SDR into the field, when a traditional battery-powered radio is so much easier to manage?

After all, you may say, portable and even mobile tabletop receivers require no computer, no hard drive, and are likely more reliable because there are less components to manage or to cause problems for you.

In answer, let’s look at a few scenarios where heading to the field with an SDR system might just make sense.  (Hint: Many of these reasons are rooted in the SDR’s ability to record spectrum).

Good Reason #1:  Your home location is not ideal for playing radio.

Photo by Henry Be

My good friend, London Shortwave, lives in the middle of London, England. He’s an avid radio enthusiast and DXer, but his apartment is almost a perfect storm of radio interference. Listening from his home is challenging, to say the least: he can only use indoor antennas and RFI/QRM simply inundated his local airwaves.

Many years ago, he discovered that the best way to DX was to go to an area that put urban noise and radio interference at a distance.  He found that by visiting large local parks, he could play radio with almost no RFI.

Being a computer guru, he started working on a portable SDR setup so that he could go to a park, set up an antenna, and record radio spectrum while he read a book.  His systems evolved with time, each iteration being more compact less conspicuous that the previous. Later, he could head back home, open the recorded spectrum files, and tune through these “time-shifted” recordings in the comfort of his flat. This allowed London Shortwave to maximize the low-RFI listening experience by reliving the time in the park.

Over the years, he tweaked and adapted his setup, often writing his own code to make small tablets and portable computers purpose-built portable-spectrum-capture devices. If you’re curious, you might like to read about the evolution of his systems on his blog.

Clearly, for London Shortwave, an SDR is the right way to capture spectrum and thus likely the best solution for his DX listening.

Good Reason #2:  Weak-signal workarounds.

Typically radio enthusiasts turn to field operation to work in a lower-noise environment and/or where there are no antenna restrictions, often to log new stations and DX.

SDRs afford the DXer top-shelf tools for digging weak signals out of the muck. SDR applications have advanced tools for tweaking AGC settings, synchronous detectors, filters, noise reduction, and even to tailor audio.

The WinRadio Excalibur application even includes a waterfall display which represents the entire HF band (selectable 30 MHz or 50 MHz in width)

On top of that, being able to see a swath of spectrum and waterfall gives one an easier way––a visual way––to pinpoint weak or intermittent signals. This is much harder to do with a legacy radio.

Case in point:  I like listening to pirate radio stations on shortwave. With a spectrum display, I can see when a new station may be tuning up on the band so can position the receiver to listen in from the beginning of the broadcast, and never miss a beat.

Or, in another example, the visual aspect of spectrum display means I can easily locate trans-Atlantic DX on the mediumwave bands by looking for carrier peaks on the spectrum display outside the standard North American 10 kHz spacing. The signals are very easy to spot.

Good Reason #3: DXpeditions both small and large.

Mark Fahey, scanning the bands with his WinRadio Excalibur/Surface Pro 2 combo at our 2015 PARI DXpedition

Whether you’re joining an organized DXpedition or you’re simply enjoying a little vacation DXpedition, SDRs allow you to make the most of your radio time.

Indeed, most of the organized DXpedition these days heavily incorporate the use of SDRs specifically so DXers can record spectrum. Much like example #1 above, doing this allows you to enjoy the noise-free optimal conditions over and over again through spectrum recordings. Most DXpeditioners will have an SDR making recordings while they use another receiver to DX in real time. Later, they take the recording home and dig even more weak signals out of the mix: ones that might have otherwise gone unnoticed.

Good Reason #4: Sharing the spectrum with like-minded listeners.

Earlier this year, Mark gave me this 8TB hard drive chock-full of spectrum recordings.

One of the joys I’ve discovered  in making field spectrum recordings is sharing them with fellow DXers. Most of the time when I go to shortwave radio gatherings (like the Winter SWL Fest), I take a couple hard drives to exchange with other SDR enthusiasts. My friend, Mark Fahey, and I have exchanged some of our favorite spectrum recordings this way. I give him a hard drive chock-full of terabytes of recordings, and he reciprocates. Back home (or on the train or airplane) I open one of his recordings and, boom! there I am in his shack in Freeman’s Reach, Australia, tuning through Pacific stations that are not easily heard here in North America, maybe even turning up some gems Mark himself may have overlooked…just as he is doing with my recordings from the southeast US.

I’ve also acquired DXpedition spectrum recordings this way. It’s great fun to “be there” through the recordings and to enjoy some of the benefits of being on the DXpedition in times when I couldn’t actually make it there in person. For a DXer with a consuming job, busy family life, or maybe health problems that limit their travel, an SDR recording is the way to go.

Good Reason #5: Family time

Photo by David Straight

I’m a husband and father, and no matter how much I like to play radio when we’re on vacation, my family comes first, and our family activities take priority.

Having a field-portable SDR setup means that I can arrange a “set it and forget it” spectrum capture device. Before we head out the door for a family visit, tour of the area, or a hike, I simply set my SDR to record spectrum, then listen to what I “caught” after I return, or after I’m home from vacation.

This practice has allowed me to enjoy radio as much as I like, without interrupting our family adventures. Can’t beat it!

Past challenges

With all of these benefits, one might wonder why many other DXers  haven’t been using portable SDRs in the field for a while now? That’s a good question.

Power

The WinRadio G31DDC, like many SDRs of the era, has separate data and power ports

In prior years, DXers and listeners might have been reluctant to lug an SDR and its requisite apparatus out with them. After all, it’s only been in the past decade or so that SDRs haven’t required a separate custom power supply; some legacy SDRs either required an odd voltage, or as with my WinRadio Excalibur, have very tight voltage tolerances.

Originally, taking an SDR to the field––especially in places without grid mains power––usually meant you also had to take a pricey pure sine wave inverter as well as a battery with enough capacity to run the SDR for hours on end.

Having spent many months in an off-grid cabin on the east coast of Prince Edward Island, Canada, I can confidently say it’s an ideal spot for DXing: I can erect large wire antennas there, it’s on salt water, and there are literally no locally-generated man-man noises to spoil my fun.  Of course, anytime we go to the cottage, I record spectrum, too, as this is truly a honey of a listening spot.

The view from our off-grid cabin on PEI.

The first year I took an SDR to the cabin, I made a newbie mistake:  it never dawned on me until I arrived and began to put it to use that my Goal Zero portable battery pack didn’t have a pure sine wave inverter; rather, I found it had a modified sine wave inverter built into it. The inverter could easily power my SDR, sure, but it also injected incredibly strong, unavoidable broadband noise into the mix. It rendered my whole setup absolutely useless. I gave up on the SDR on that trip.

Both the Airspy HF+ (top) and FDM-S2 (bottom) use a USB connection for both data transfer and power. Photo by Guy Atkins.

Today, most SDRs actually derive their power from a computer or laptop through a USB cable, one that doubles as a data and power cable. This effectively eliminates the need for a separate power system and inverter.

Of course, your laptop or tablet will need a means of recharging in the field because the attached SDR will drain its battery a little faster. Nowadays it’s possible to find any number of portable power packs/banks and/or DC battery sources to power laptops or tablets, as long as one is cautious that the system doesn’t inject noise. This still requires a little trial and error, but it’s much easier to remedy than having two separate power sources.

Portable computers

Even a Raspberry Pi 3B has enough horsepower to run SDR applications.

An SDR is nothing without a software application to run it. These applications, of course, require some type of computer.

I the past, SDR applications needed some computing horsepower, not necessarily to run the application itself, but to make spectrum recordings.  In addition, they often required extra on-board storage space to make these recordings sufficiently long to be useful.  This almost always meant lugging a full-sized laptop to the field, or else investing in a very pricey tablet with a hefty amount of internal storage to take along.

Today we’re fortunate to have a number of more portable computing devices to run SDR applications in the field: not just laptops or tablets, but mobile phones and even mini computers, like the eminently affordable $46 Raspberry Pi. While you still have to be conscious of your device’s computing horsepower, many small devices are amply equipped to do the job.

Storage

64-128 GB USB flash/thumb drives are affordable, portable storage options.

If you’re making spectrum and audio recordings in the field, you’ll need to store them somehow. Wideband spectrum recordings can use upwards of 2GB of data per minute or two.

Fortunately, even a 64GB USB flash drive can be purchased for as little as $7-10 US. This makes for quick off-loading of spectrum recordings from a device’s internal memory.

My portable SDR setup

It wasn’t until this year that all of the pieces finally came together for me so that I could enjoy a capable (and affordable!) field-portable SDR setup. Two components, in particular, made my setup a reality overnight; here’s what made the difference.

The AirSpy HF+ Discovery

Last year, AirSpy sent me a sample of their new HF+ Discovery SDR to test and evaluate. To be fully transparent, this was at no cost to me.

I set about putting the HF+ Discovery through its paces. Very soon, I reached a conclusion:  the HF+ Discovery is simply one of the best mediumwave and HF SDRs I’ve ever tested. Certainly, it’s the new benchmark for sub-$500 SDRs.

In fact, I was blown away. The diminutive HF+ Discovery even gives some of my other benchmark SDRs a proper run for their money. Performance is DX-grade and uncompromising, sporting impressive dynamic range and superb sensitivity and selectivity. The noise floor is also incredibly low. And I still can’t wrap my mind around the fact that you can purchase this SDR for just $169 US.

The HF+ Discovery compared in size to a DVD

In terms of portability, it’s in a class of its own. It’s tiny and incredibly lightweight. I evaluate and review SDRs all the time, but I’ve never known one that offers this performance in such a tiny package.

Are there any downsides to the HF+ Discovery? The only one I see––and it’s intentional––is that it has a smaller working bandwidth than many other similar SDRs at 768 kHz (although only recently, Airspy announced a firmware update that will increase bandwidth). Keep in mind, however, that the HF+ series SDRs were designed to prevent overload when in the presence of strong local signals. In fairness, that’s a compromise I’ll happily make.

Indeed, the HF+ Discovery maximum bandwidth isn’t a negative in my estimation unless I’m trying to grab the entire mediumwave band, all at once. For shortwave work, it’s fine because it can typically cover an entire broadcast band, allowing me to make useful spectrum recordings.

The HF+ Discovery is so remarkably tiny, that this little SDR, together with a passive loop antenna, can fit in one small travel pouch. Ideal.

The antennas

My homebrew NCPL antenna

Speaking of antennas, one of the primary reasons I’m evaluating the HF+ Discovery is because it has a very high dynamic range and can take advantage of simple antennas, in the form of passive wideband magnetic loop antennas, to achieve serious DX.

AirSpy president and engineer, Youssef Touil, experimented with several passive loop antenna designs and sizes until he found a few combinations ideally matched with the HF+ Discovery.

My good buddy, Vlado (N3CZ) helped me build such an antenna per Youssef’s specifications. Vlado had a length of Wireman Flexi 4XL that was ideal for this project (thanks, Vlad!). The only tricky part was penetrating the shielding and dielectric core at the bottom of the loop, then tapping into both sides of the center conductor for the balun connections.  Being Vlado, he used several lengths of heat shrink tubing to make a nice, clean, snag-free design. I’ll freely admit that, had I constructed this on my own, it wouldn’t have been nearly as elegant!

Click here for a step-by-step guide to building your own NCPL (Noise-Cancelling Passive Loop Antenna.

Youssef also sent me a (then) prototype Youloop passive loop antenna. It’s incredibly compact, made of high quality SMA-fitted coaxial cables. It can be set up in about 30 seconds and coiled to tuck into a jacket pocket.  The AirSpy-built loop has a lower loss transformer than the one in the homemade loop, which translates into a lower noise figure for the system.

Click here to read my review of the Youloop.

Let’s face it: SDR kit simply doesn’t get more portable than this.

The computer

My Microsoft Surface Go tablet on a hotel bed.

In the past, I used an inexpensive, circa 2013 mini Windows laptop with an internal SSD drive.  Everything worked beautifully, save the fact that it was challenging to power in the field and the internal capacity of the hard drive was so small (16GB less the operating system). In addition, it was a few years old, bought used, so the processor speed was quite slow.

This year, on the way back from the Huntsville Hamfest, I stopped by the Unclaimed Baggage Center in Scottsboro, Alabama. This center has a wide variety of used portable electronics at discount prices. I felt pretty lucky when I discovered a like-new condition Microsoft Surface Go tablet and keyboard with original charger for $190. The catch? The only data port on the tablet is a USB-C. But I grabbed a small USB-C to standard USB 3.0 dongle (for $2!) and took a risk that it would work with the HF+ Discovery.

Fortunately, it did! Score!

While the Surface Go is no powerhouse, it’s fast enough to run any of my SDRs and make spectrum recordings up to 2 MHz in width without stuttering. The only noise it seems to inject into the mix is a little RFI when I touch the trackpad on the attached keyboard.

Power

One of my LiFePo batteries

The HF+ Discovery draws power from the Surface Go tablet via the USB port. With no additional power supply, the Surface Go may only power the HF+ Discovery for perhaps an hour at most. Since I like doing fully off-grid operations and needed to avoid RFI from inverters, I needed a portable power solution.

Fortunately, the Surface Go has a dedicated power port, so I immediately ordered a DC power cable with a standard car lighter plug.

At the Huntsville Hamfest I also purchased a small 12V 4.5 Ah Bioenno LiFePo battery and paired it with a compact Powerpole distribution panel kit I purchased in May at the 2019 Dayton Hamvention.

The LiFePo battery is small, lightweight, and can power the tablet /SDR combo for hours on end. Moreover, I have noticed no extra noise injected when the DC power is applied.

My HF+ Discovery-based portable SDR kit

My portable SDR kit on a hotel balcony.

Now I have this kit, I couldn’t be more pleased with it. When all of the components of my SDR system are assembled, they work harmoniously. The entire ensemble is also incredibly compact:  the loop antennas, SDR, Surface Go tablet, battery, and distribution panel all fit in a very small travel pack, perfect for the grab-and-go DX adventure.

The entire kit: SDR, cables, Youloop antenna, connectors and adapters all fit in my Red Oxx Lil’ Roy pack.

In November, I took the kit to the coast of South Carolina and had a blast doing a little mediumwave DXing from our hotel balcony. We were very fortunate in that I had two excellent spots to hang the homemade loop antenna: on the main balcony, and from the mini balcony off the master bedroom. Both spots yielded excellent results.

What impressed me most was the fact that the SDR# spectrum display and waterfall were absolutely chock-full of signals, and there was very little noise, even in the popular resort area where we were staying. I found that my portable radios struggled with some of the RFI emanating from the hotel, but the HF+ Discovery and passive loop combo did a much better job mitigating noise.

Check out the AM broadcast band on the spectrum display.

But no need to take my word for it.  If you would like to experience it first hand, why not download an actual spectrum recording I made using this setup?

All you’ll need to do is:

  1. Download the 1.7 GB (.wav formatted) spectrum file at this address
  2. Download a copy of SDR# if you don’t already have an SDR application that can read AirSpy spectrum files.
  3. Install SDR#, and run it.
  4. At the top left corner of the SDR# screen, choose “IQ File (.wav)” as the source, then point it to where you downloaded the file.
  5. Press the play button, and experience a little radio time travel!

This particular recording was made on the mediumwave band on November 17, 2019, starting at around 01:55 UTC.

My portable SDR kit capturing spectrum during a hike in Pisgah National Forest.

I’ve also taken this setup to several parks and remote outdoor locations, and truly enjoyed the freedom of taking spectrum recordings back home to dig through the signals.

Conclusion

I finally have a portable SDR system that allows me the flexibility to make spectrum recordings while travelling. The whole setup is compact and can easily be taken in a carry-on bag when flying.

The glory of this is, I can tune through my spectrum recordings in real time and DX when I’m back home, or even on the way back home, in the car, train, or airplane. It’s simply brilliant.

If you don’t already own an SDR, I can highly recommend the AirSpy HF+ Discovery if you’re primarily interested in HF and MW DXing. If you need a wideband SDR, I could also recommend the recently released SDRplay RSPdx, although it’s slightly heavier and larger than the AirSpy.

Thankfully, I am now an SDR enthusiast that can operate in the field, and this radio has had a lot to do with it. I’ll be logging many hours and miles with the AirSpy HF+ Discovery: its incredibly compact footprint, combined with its brilliant performance, is truly a winning combo.

Click here to check out the Airspy HF+ Discovery

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Super cheap Walmart soap bar holder transforms into an ideal portable radio stand

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Many thanks to SWLing Post contributor, Shawn Bliss (KB7WYO), who writes:

Hi, Thomas! I love the blog and check in every day or two to get my SWL fix. I recently purchased a PL-310ET on your recommendation (and those of many other radio people) and absolutely love it. My previous porch radio was a well-worn and filthy Grundig G8 Traveler II which of course suffered a broken kickstand soon after its purchase many years ago. Wanting to avoid the same problem with the 310, I figured I might be able to improvise a stand out of some household item, and a trip to a local big box store today proved extremely fruitful in that respect!

As I wandered through the kitchen accessories at Walmart, I spotted a little black sink caddy, typically used to hold a dish sponge and hang on a sink or faucet. I grabbed it, paid a little under four bucks for it, and took it home. It’s a cheap, lightweight, and adjustable stand for small to midsize radios.

The caddy is essentially a loop of flexible, bendable rubber-coated wire with a perforated rubber cradle for the sponge. Because it can be bent and shaped, it’s ideal for adjusting to different sized portables. In its default shape from the store, it held the 310ET, the G8, my Tivdio V-115, and other smaller items like my phone and e-reader.

I’m sure it could be bent to fit a PL-660, PL-880, Eton Satellit, XHDATA D-808, and other larger portables, all at adjustable back angles.

Best of all, the caddy can be bent down to fit into a go-bag or piece of travel luggage. I figure a fellow pack-nut like yourself would find this to be useful indeed!

These things are cheap and readily available at pretty much every Walmart, but I’ll post a link to the webpage for the Mainstays Flexible Sink Caddy. I hope this info is useful to other SWLs and hams. I instantly thought of the Post and your gear/accessory posts in the past when I saw it.

https://www.walmart.com/ip/Mainstays-Flexible-Sink-Caddy/480104340

What a great idea, Shawn! Since this soap bar holder is so flexible, it could be bent to hold radios at pretty much any angle. Next time I’m at Walmart, I’ll pick one up. Perhaps this is even available at Walmart stores in other countries since it’s sold under the Mainstays brand name.

I believe this holder could also serve as a stand for numerous portable QRP transceivers.

Thanks again for the amazing tip, Shawn!

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The Tecsun PL-330: Some details about this compact shortwave portable in development

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Source: tecsun.com.cn

Many thanks to a number of SWLing Post readers who shared a link to this website (in Chinese) with photos and details of the new Tecsun PL-330. Note: The server hosting the PL-330 page has been unreliable the past few days.

Some of you might recall the PL-330 in photos of the new Tecsun product line we posted last year. Recently, a handful of preliminary working prototypes have been produced,  so I reached out to my trusted Tecsun contact for more information. Here’s what I’ve learned:

Position in Tecsun product line

In terms of the Tecsun product line, the PL-330 appears to be the successor to the venerable Tecsun PL-310ET and/or PL-380.

The PL-330 will have features these legacy Tecsun models do not have, namely:

  • synchronous detection,
  • single-sideband reception,
  • and an upgraded ETM (auto tune and store) feature.

It also appears the SSB tuning steps could be as fine as 10 Hz. Most impressive, if true.

Size

Size comparison: PL-330 (left), PL-990 (middle), H-501 (right)

I refer to radios in this size class as “ultra-compact.”

The PL-330 measures 139 × 85 × 26 millimeters (5.5 x 3.3 x 1 inches). Its form factor is very similar to the PL-310ET, but much thinner in profile. The total depth of the radio is only 26 mm.

I love the idea of an even thinner profile, although this certainly limits the type of internal battery that can be used.

Battery

The PL-330 is powered by a single BL-5C lithium battery.

In my world, this is a bit of a negative, but I’m sure the BL-5C was one of the only viable battery options for a radio that’s only 26mm thick.

On the plus side, the BL-5C is widely available, affordable, and can be charged internally.

On the negative side?

Well, I find that the overall capacity doesn’t match that of, say, three AA batteries. Also, I find that the battery’s longevity (meaning, how many charge cycles it can handle) is not that impressive–arguably worse than any other rechargeable battery system I’ve used.

Another reason I prefer AA batteries in compact portables is I know no matter where I travel, I can easily purchase them at almost any retailer, airport, or even hotel, in a pinch. In the past, when I’ve traveled with radios that use the BL-5C, I simply carried a fully-charged spare in a poly zip-lock bag (to protect the battery contacts from inadvertently shorting.

In addition, when I fly, I like to carry as few Lithium batteries as possible.

Perhaps, however, I can find a very high quality BL-5C to use in the PL-330? I would appreciate any leads from readers.

Performance

Since the preliminary prototypes were more or less mechanical prototypes and lacked most of the features planned for this model, there are no performance reports as of yet. In fact, I would be skeptical of any reports you might read in advance of the final production model.

Availability

Like the PL-990 and H-501, there are no reliable estimates for availability or shipping yet. The Covid-19 pandemic has slowed down this process. Most likely, the PL-330 will be released after the PL-990 and H-501, but that isn’t even certain.

Stay tuned!

The PL-330 will have a number of other features and specs, but these are early days and I prefer sticking with what we do know now. As soon as I learn more, I’ll post updates–bookmark the tag PL-330.

Note this reddit thread with an English translation of the Chinese page I mentioned at the beginning of this article (thanks, Tom Daly). It mentions more details, but again, it’s such early days I prefer to stick with what has been confirmed. As with any product in development, a number of changes could occur before the first production run.

Of course, I will review and evaluate the export version of the PL-330 when as soon as it’s available. Stay tuned!

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Five solid radios to get you through the pandemic (or any emergency, for that matter)

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The original CC Skywave portable radio is among the pricier of my suggestions, but also packs the most features. Seen here on location in Canada.

Over the past four weeks, I’ve gotten a number of emails from first-time readers of the SWLing Post who’ve landed here because they’re searching for a new radio. While not all these readers are necessarily interested in shortwave, what they are interested in is a good, solid battery-powered radio to receive local news on AM and FM.  A few have specifically asked for a radio with NOAA/Environment Canada weather radio reception. Others are looking for a self-powered or hand crank radio option, while some specifically asked for a shortwave radio to listen to international broadcasts. A common point was that no one wanted to spend a lot, inclining toward something cost-effective––understandable in these uncertain times––but they nonetheless are looking for quality, for a radio that won’t fail them, even if their Internet service does.

Radios provide local connection

The following post is my response to these questions. I’ve selected five radios under $90 USD that can fill a variety of needs, and also offer good information support in the event of an emergency. I gave priority to radios that can be powered by common AA batteries––all but one model can be powered by common AA cells. Also, three of the five radios below can receive North American weather radio frequencies.

Note that while many of these models have been chosen with North American readers in mind, there are a number of similar models available in Europe, Asia, and the Pacific that have DAB/DAB+ reception. This list is by no means comprehensive, as there are literally hundreds of similar radios on the market; if you feel I’ve left an ideal radio off this list, please feel free to share your thoughts in the comments section.

Self-Powered Radios: The C. Crane CC Solar Observer ($50)

There are a number of self-powered (hand-crank and/or solar powered) radios on the market. My favorite self-powered radio for receiving local news and weather here in North America is the C. Crane CC Solar Observer.

I like the CC Solar Observer because it’s substantial, well made by a company I trust, and has three different ways to power it (AA batteries/AC adapter, a hand crank, and solar charging). The internal rechargeable battery pack stores energy from the hand crank, solar panel, or AC adapter. In a pinch, this radio can even charge a mobile phone via a supplied USB adapter.

The backlit dial is such a thoughtful design feature: whether the power’s out or you’re just out camping, it’s good to be able to see where you’re tuning in.

And, of course, this radio performs very well, indeed. You’ll be pleased with AM, FM and weather radio reception. Audio is quite respectable via the internal speaker, and the overall build quality is excellent. The CC Solar Observer also sports an LED flashlight, and is, to my knowledge, the only self-powered radio with a very handy backlit dial!

This is not the cheapest in the line-up: new, these retail anywhere from $45 to $60 USD. Still, I think this radio is a very worthwhile investment, and really, the best of the bunch.

Retailers:

Other Options: The Degen DE13 DSP is much smaller, sports the shortwave band, and is less expensive (roughly $25 USD). I also like the Tecsun GR-88, which has a similar form factor to the CC Solar Observer, and also includes the shortwave bands (roughly $55 USD). Negatives for both of these radios is that many are sold from China, which could mean longer-than-normal shipping times, should you need it soon. Also, neither of these models include North American weather radio frequencies.

For more emergency radios, also check out Eton Corporation’s offerings.

Simple Pocket Radios With Built-In Speaker: Sangean SR-35 ($20)

Small form factor ideal for you? I like the Sangean SR-35 because it’s such a simple, easy-to-use radio, is obviously incredibly portable, and produces respectable audio for a pocket radio. (The SR-35 is also a favorite among SWLing Post readers.) The SR-35 sports an 18” telescopic FM antenna and built-in AM antenna. Performance is fantastic for a radio in this price class. If you don’t mind an analog dial and the fact the SR-35 can’t receive North American weather radio frequencies, you’ll love this affordable little pocket radio.

Retailers:

Other Options: Although the Sangean DT-800 is pricier (roughly $55 via Amazon, $79 via Universal Radio) it includes weather radio reception and even weather alerts––click here for my full review. The C. Crane CC Pocket is very similar to the DT-800, and retails for $65 via C. Crane, $60 via Universal, and $65 via Amazon. I’m also a massive fan of the Sony ICF-S10MKII for its AM/FM performance and superb battery life, but unfortunately it’s no longer in production, so your best bet is to look for one on eBay.

Battery Endurance Radios: Sangean DT-160 ($50)

I like the Sangean DT-160 because it’s a respectable AM/FM portable radio that can run on two AA batteries for an impressive 116 hours. I can confirm this because I once tested its clear-case cousin, the DT-160CL. It’s very compact, and sports excellent FM and AM performance that will snag all of your local broadcasters. Unlike some of the other selections on this page, it lacks an internal speaker and North American weather radio frequencies. Still, if you’re looking for a pocket portable with digital display that’s an incredible battery miser, look no further than the Sangean DT-160.

Retailers:

Other Options: I’ve only tested a handful of radios for battery performance. The DT-160 is certainly king in this category, although no doubt there are many analog models that could achieve even better battery longevity. The models that have impressed me the most both in terms of performance and battery life are the Sony SRF-59 and SRF-39FP (clear case). Sadly, neither of these models is still in production, but you can still track down used ones on eBay.

Large Portable Radios: Sangean PR-D4W ($65)

Sangean radios are a favorite among SWLing Post readers because they’re built well and typically perform exactly as they should. In fact, when I mentioned I would be writing this post, several readers immediately suggested the Sangean “PR” series radios, and perhaps my pick of this bunch is the venerable Sangean PR-D4W. I like this particular model because it receives AM, FM and North American weather radio frequencies. It even has a weather alert function. Audio from the built-in speaker is pleasing and operation is very simple. Most functions are available via one-button press. Note that Sangean also produces a PR model for visually-impaired customers that is similar to the PR-D4W, although it lacks weather radio; this is the Sangean PR-D17 (click here to read a full review). The only gripe I have with the PR-D4W (and many of the “PR” series radios) is a lack of carry handle. Unlike the other radios in this list, the PR-D4W requires four “D” cells for battery operation.

Retailers:

Other Options: Click here to check out the full line of Sangean “PR” series radios.

Portable Shortwave Radios: C. Crane CC Skywave ($85)

The C.Crane CC Skywave

The CC Skywave is a brilliant little radio and is certainly time-tested. It’s a fine broadcast receiver and one of the most sensitive travel portables on the market. For those of us living and traveling in North America, the CC Skywave is a veritable “Swiss Army Knife” receiver, as it not only covers AM, FM and shortwave, but is a capable AIR band receiver plus incredibly adept NOAA/Environment Canada weather radio receiver. At $90 USD, I believe it’s the best radio value in the C. Crane product line. Click here to read our full review of the CC Skywave.

Retailers:

Other Options: Although it lacks North American weather radio reception and no AIR band like the CC Skywave, the Tecsun PL-310ET is a time-tested benchmark portable radio. At $48 shipped (via Amazon), it’s a bargain. An even less expensive option is the Retekess V115, at $29.99 shipped, and though its performance is pretty impressive for the price, I prefer the overall quality of the Tecsun and C. Crane better.

Summary

If you’ve found this post because you’re looking for a reliable AM/FM radio, I hope the selections above will give you some guidance. There are so many AM/FM radios on the market, we can’t cover them all.  But these solid radios are time tested, and in my view, among the best; they’re not likely to let you down when you need them most.

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DIY: How to build a Noise-Cancelling Passive Loop (NCPL) antenna

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I’ve gotten an number of inquiries from SWLing Post readers asking for a step-by-step guide to building the passive loop antenna I’ve mentioned in a number of previous posts. This antenna is the homebrew version of the commercially-available  Airspy Youloop.

It works a treat. And, yes, folks…it’s fun to build.

There are a number of loop designs out there, and to distinguish this one, I’m going to henceforth refer to this loop as in the title above:  the Noise-Cancelling Passive Loop (NCPL) antenna.

Before we start building, a little antenna theory…

I’m neither an engineer nor am I an antenna expert, so I actually turned to Airspy president and engineer, Youssef Touil, to learn how, exactly, this passive loop works. Youssef was the guy who experimented with several loop designs and ultimately inspired me to build this loop to pair with his HF+ Discovery SDR and the SDRplay RSPdx. “The main characteristic of this loop,” Youssef notes,  “is its ability to cancel the electric noise much better than simpler loop designs.” Got that!  [See loop diagram below]

“The second characteristic of this loop antenna is that it is a high impedance loop, which might appear counterintuitive. This means it can work directly with many receivers that have a low noise figure, in order to mitigate the impedance mismatch loss.

Note the resonance lobe near 4MHz. The resonance frequency is controlled by the diameter of the loop, the parasitic capacitance of the cable, and the loading from the transformer. It happens to be located right where we need it the most.

The transformer is basically a 1:1 BALUN that covers the entire HF band with minimal loss. Our BALUN has typically 0.28 dB loss.

[…]By connecting the center of this outer shield to the ground of the transmission line, you effectively cancel all the electric noise. The BALUN is required for balancing the electric noise, not for adapting the impedance.

[…]If you want to boost the performance in VLF, LW and MW, you can try a different impedance ratio, but this will kill the higher bands.”

What makes this loop so appealing (to me) is that it can be built with very few and common parts–indeed, many of us have all of the items in our junk boxes already. As the name implies, it is a passive design, so it requires no power source which is incredibly handy when you’re operating portable.

When paired with a high-dynamic range SDR like the Airspy HF+ Discovery or SDRplay RSPdx, you’ll be pleased with the wide bandwidth of this antenna and noise-cancelling properties.

If you don’t care to build this antenna, Airspy sells their own version of this loop for a modest $35 USD.

But building an antenna is fun and you can tweak the design to customize performance, so let’s get started:

Parts list

  • A length* of coaxial cable for the loop (see notes below regarding length)
  • Another length of cable terminated on one end with a connector of your choice as a feed line
  • A BN-73-302 Wideband 2-hole Ferrite Core
  • Enough coated magnet wire for a total of eight turns on the BN-73-302
  • Heat-shrink tubing or some other means to enclose and secure the cable cross-over point and balun. (You may be able to enclose these connection points with PVC or small electrical box enclosures, for example)
  • Electrical tape

Tools

  • A cable stripper, knife, and/or box-cutter
  • Soldering iron and solder
  • A heat gun (if using heat shrink)
  • Some patience 

*A note about loop cable length: Vlado and I made a loop with 1.5 meters of cable. The Airspy Youloop ships with two 1 meter legs that combine to give you an overall loop diameter of about 63.6 cm.

Step-by-step guide

When I first decided to build this loop, it was only a day prior to a trip to the South Carolina coast where I planned to do a little DXing. I didn’t have all of the components, so I popped by to see my buddy Valdo (N3CZ). Vlado, fortunately, had all of the components and was eager to help build this loop. As I’ve mentioned in previous posts, Vlado is an amazing engineer and repair technician, so when I say “we” built it, what I really mean is, Vlado did!  But I could’ve done it myself.

This is actually a very simple build––something even a beginner can do, as long as they’re okay with using a soldering iron. It does take patience preparing the loop cable properly. Take your time as you start, and you’ll be on the air in an hour or two.

1. Strip the ends of the loop cable.

Although your cable type and diameter may vary, strip back the cable ends roughly like this.
To make finding the middle of the cable easier, we taped off the ends.

2. Make an opening in the middle of the cable to attach Balun leads to center conductor.

This is the trickiest part of the whole operation. The goal is to create an opening to tap into the center conductor of the cable.

You need to open a hole in the middle of the cable by

1 cutting away a portion of the outer jacket;

2 carefully separating and opening the shielding;

3 digging through the dielectric core, and finally

4 exposing the center conductor of the cable

Try to make an opening just large enough to gain access to the cable’s center conductor, but no bigger. Don’t allow any piece of the shielding to touch the center conductor.

When you reach the center conductor, expose enough of it so that you can clip it in the middle and create an opening to solder your balun leads to both conductor ends.

Once you’ve finished with this step, your cable should look something like this…

In the photo above, note that the shielding is completely pulled away, the dielectric core has been cut through, and we’ve clipped the center conductor, leaving a gap large enough to solder.

3.  Make a 1:1 Balun

Grab your BN-73-302, and with the coated magnet wire, make four windings on one side, and four on the other. It should look like this:

Don’t have a binocular ferrite core like the one above? If you have a broken cable with ferrite cores, you can hack one! Click here to learn more.

4. Connect the Balun to a feed line.

Vlado just happened to have a BNC pigtail in his shack (he’s that kind of guy), so we cut and stripped one end, then connected the center conductor and shield to one side of the balun. We then enclosed the balun in heat shrink tubing to make it a little easier to attach to the loop later:

Of course, you could also create this junction in a small enclosure box or short cross-section of PVC. There are a number of ways you could secure this.

Youssef also added the following note about the feedline:

To use the NCPL antenna without a preamp, it is recommended to keep the length of the cable below 10 meters. The supplied Youloop 2 meter cable [for example] is sufficient to keep the antenna away from the magnetic interference of a computer or a tablet, and has very low loss and parasitic capacitance.

5. Connect Balun to the coaxial loop.

To make a solid connection, tin both sides of the center conductor. Next, attach the other end of the balun leads to each portion of the center conductor, as seen below:

Update: Note in the loop diagram near the top of the page that the ground wire on the output connector connects to the loop coax shielding on the primary side of the balun. I don’t recall that we did this in the build, but I would encourage you to do so. This should result in even lower noise, although admittedly, I’m very impressed with the performance of ours without this connection. Thanks to those of you who pointed out this discrepancy!

6. Secure the Balun/Coax junction.

Since this loop is intended to be handled quite a lot in the field, make sure the junction point of the balun and coax loop is secure. Again, we used several layers of heat shrink tubing since we had some in the shack.

7. Solder and secure the cross-over point.

Next, create the cross-over point of the loop by simply attaching the center conductor of one end of the cable to the shielding on the other end…and vice versa.

Before you grab the soldering iron, however…if, like we did, you’re using heat shrink tubing to secure the cross-over point of the loop in the next step, you’ll first need to slide a length of tubing onto the coax before you solder the ends together. Vlado, of course, thought of this in advance…I’m not so certain I would have!

Take your time soldering this connection and making it as solid as you can. If you solder it correctly, and you’re using a high-quality cable as we did, the cross-over point will be surprisingly durable. If you’re using a thinner cable, simply make sure the connection is solid, then use something to make the junction less prone to breaking––for example, consider sealing a length of semi-rigid tubing around this point.

Vlado cleverly added heat shrink tubing around the cross-over point to protect and secure it.

You’re done!

That’s all, folks! Now you’re ready to put your loop on the air.

Depending on what type of cable you used for this loop, you might require or prefer some sort of dielectric structure to support the loop so that it maintains the ideal round shape. My loop maintains its integrity pretty well without supports. I’ve supported it a number of times with fishing line/filament from two sides (tying on at 10 and 2 o’clock on the loop). That seems to work rather well.

In this setup, I simply used the back of a rocking chair to hold the antenna. As you can see, the loop maintained its shape rather well.

If you’d like to see and hear how this antenna performed on its first outing, check out this post.

Show the Post your loop!

If you build a NCPL antenna, please consider sharing your design here on the SWLing Post! Considering that there are a number of ways this loop can be built, and likely even more optimizations to improve it or make its construction even easier, we’d love to see your designs and/or construction methods. Please comment or, if you prefer, contact me.

And many thanks to my good friend Vlado (N3CZ)  for helping me with this project and allowing me to document the process to share it here on the Post. Got a radio in need? Vlado’s the doctor!

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A Compact RSPdx & Wellbrook Loop Kit for the Beach — My Approach

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I have enjoyed three to four medium wave and shortwave DXpeditions per year since 1988, to sites on the Washington and Oregon coasts. I love the chance they give to experiment with antennas in a (hopefully!) noise-free location, and concentrate on catching stations that might not be heard from home.

All of my DX trips have been via car–until now! I’ve just returned from nine vacation days in Hawaii (Waikoloa Beach, on the Big Island), and I thought others might like to see the radio related items I chose to take along for air travel. I’m pleased to report that everything worked as planned, and I have five days of SDR IQ WAV files of the MW band for review, all recorded in the time frame surrounding local dawn.

My goal was not the smallest, most compact portable setup, but one with high performance and modest size. Fitting everything into a day pack was another requirement. A simple wire antenna and an even smaller Windows tablet or laptop than the one I’ve used (and a smaller SDR like the HF+ Discovery, for that matter) would make a much smaller package. However, the items I’ve assembled worked excellently for me during my enjoyable Hawaii vacation. The directional loop antenna provided nulls on medium wave of 30 dB during preliminary tests indoors, a less-than-ideal test situation.

Waikoloa Beach–just one of a zillion picturesque scenes in Hawaii.

Here is a list of what I’ve put together for my DXing “kit”:

    • SDRPlay RSPdx receiver
    • Short USB cable for receiver<>PC connection, with two RFI chokes installed
    • Lenovo X1 tablet— a Windows 10 device with magnetically attached keyboard; this model is a competitor to Microsoft’s Surface Pro tablet
    • Wellbrook Communications’ ALA1530 head amp module, modified for female SO239 connectors enabling use of large diameter LMR-600 coaxial cable as a 2-turn loop element. My antenna setup is similar to Wellbrook’s commercial flexible loop
    • Wooden base for the antenna (ALA1530 is bolted to the base)
    • 20 feet of lightweight RG-174 coax
    • Wellbrook DC interface module for the ALA1530
    • 3.0 Ah LiFePO4 rechargeable battery for the Wellbrook antenna
    • 15 foot long section of high grade “Times Mfg.” LMR-600 coax cable with PL259 connectors (bought from Ebay already assembled/soldered)
    • Fold-up beach mat
    • Small day pack to hold everything

All the contents of this DXing setup fit a standard size day pack.

You’ll note the absence of headphones in the list. This is because my intent from the start was to record all the DX (MW band) as SDR WAV files for DXing post-vacation. That said, I did have headphones in my travel luggage for later spot checks of a few frequencies. That’s how I found 576 kHz Yangon, Myanmar lurking at their 1700 sign-off with national anthem and English announcement. The remainder of the DX to be uncovered will have to wait until I’m back home near Seattle!

The LMR-600 is a very thick and stiff coax cable, whose diameter approaches that used in the standard aluminum tubing ALA1530 series from Wellbrook. It has the benefit of being self-supporting in a 2-turn configuration and will also coil up into an approx. 12-inch package for transport. It just barely fits within the day pack I’m using. As I understand it, magnetic loops with tubing or large coax as the active element, versus simple wire, are more efficient in operation. Whether or not this holds true in practice remains to be seen.

I fashioned a wooden disc 3/4″ thick to attach the ALA1530 head amplifier, as I didn’t want to bring along a tripod or other support stand. The Wellbrook antennas all work well near or at ground level, so I was able to get great reception with the antenna right on the beach. The diameter at two turns of the coax is only a few inches smaller diameter than Wellbrook’s aluminum tubing loops. Three strips of strategically placed Velcro straps help keep the turns together when deployed as well as during storage.

In theory a two-turn loop should give 5 dB less gain than a single turn version; however, my older ALA1530 module has 5 dB more gain than the newer “LN” type, according to Andrew Ikin of Wellbrook Communications. The net result is that my two-turn antenna should have equal gain to the larger one-turn variety. Future experimentation with this DIY coax loop antenna is in order!

The Wellbrook loop antenna, RSPdx receiver, and Windows 10 tablet on the beach in Waikoloa, Hawaii.

Another view of the DXing position. Being this close to the water with my radio gear was unnerving at first, but the wave action on a calm Hawaii beach is totally different from the Oregon/Washington beaches with waves that can move in and out by a hundred feet or more.

The Wellbrook “DIY FlexLoop” works fine at beach level, and is less conspicuous this way, too.

The ALA1530 module is bolted to the 11-inch wooden disc for support. I’ve modified the module’s sockets to securely hold SO239 female connectors.

The commercial Wellbrook FLX1530LN is a fine product, and worthy of your consideration as a compact and high performance travel antenna. Full details can be found at this link.

SDR WAV Files for Download

One of my goals from the start for my Hawaii trip was to bring back SDR “IQ” WAV files for sharing with others. These approx. 900 Mb files cover the entire medium wave band as heard from my beach location in Waikoloa.

The overall page is: https://archive.org/details/@4nradio   Clicking on any of the entries will bring you to a details page. From there just right click on the “WAVE” link, and choose “Save as…” to download. For a few of the recordings I also posted the file that precedes the one that goes across the top-of-the-hour, because things seemed a bit more lively prior to 1700 (which  was at local sunrise, give or take a couple of minutes).

The IQ WAV files are only playable with suitable SDR radio software: SDRuno is first choice (but you need a RSP receiver connected). The files are also is compatible with HDSDR and SDR-Console V3. It may also play on Studio 1 software.

I hope other DXers enjoy the chance to tune through the MW band, as heard from the Big Island of Hawaii.

Guy Atkins is a Sr. Graphic Designer for T-Mobile and lives near Seattle, Washington.  He’s a regular contributor to the SWLing Post.

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The Sony ICF-7600A continues to impress

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I mentioned in a previous post that SWLing Post contributor, Ed Earps, recently gifted me his Sony ICF-7600A.

I’ve been having a field day with this radio!

Well, many field days, in fact. Early on, I packed the ‘7600A in my Red Oxx Hound EDC pack–it fits in the Hound’s interior pocket perfectly and is well-protected on all sides. The radio has pretty much lived in my car and truck since then, thus has gotten a lot of air time when I take short breaks throughout the day.

In November, I took the ‘7600A to Mount Mitchell (6,684 feet/2,037 meters above sea level) and to coastal South Carolina (sea level). It’s been a great radio companion and has given me an excuse to go “old school” and do a little analog band-scanning.

The ICF-7600A certainly has some strengths.

For one thing, although I’ve let this radio on for extended listening sessions, I’ve yet to deplete the eneloop rechargeable batteries (Amazon affiliate link) I originally installed in October. Obviously, this radio will run for days on batteries–a serious plus if DXing off-grid.

The ‘7600A is a fantastic portable for mediumwave DXing. Although it’s also a very sensitive and selective shortwave receiver–especially in this class and era of analog portable–I think mediumwave may be its strong suit.

On the negative side, some of the shortwave band selections are truncated and for some reason, it doesn’t have a back stand (quite an odd omission). Still, these are pretty minor cons.

Obviously, the pros outweigh the cons on this brilliant vintage portable that seems to have held up very well over the years.

To ensure its longevity–and as a precaution–I do think I’ll take it to Dr. Vlado to have all of the caps replaced soon.

My thoughts? If you ever stumble across an ICF-7600A at a hamfest or on eBay, I say grab it!

Post readers: Anyone else love the ICF-7600A? Did I miss any major pros or cons? Please comment!

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