Tag Archives: Guest Posts

Dan’s review of the flagship Tecsun H-501x portable shortwave receiver

Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post and review:

The H-501: Jewel in the Tecsun Crown, With Some Attractive Features

by Dan Robinson

Since 2020, there has been one Tecsun receiver I have been most looking forward to reviewing, and that is Tecsun’s H-501.

Videos showing the pre-production and mainland China versions of the 501 started appearing online at least a year ago. There are also numerous videos showing comparisons between the H-501 and PL-990x as well as the PL-330.

What I will do here is provide an assessment of the 501 informed by my use of a H-501 just received, the other two Tecsun receivers, and my decades of experience using a wide range of portable receivers. This review is based on initial tests of a H-501x, among the first production units.

Video: Unboxing

HOMAGE TO RECEIVERS OF THE PAST

The elephant in the room with the 501 is, of course, its two large left and right speakers. This reminds one of another Tecsun DSP portable, the PL-398BT with a similar left-right speaker arrangement.

On the left of the H-501, from the top, are the Volume, Treble, and Bass knobs which like the PL-880 and 990x has obvious lineage back to the famous Grundig portables of the 1990’s – the Satellit 500 and 700. Both of those were limited to two bandwidths. Only the 700 had anything approaching usable synchronous detection.

Each of the left hand control knobs on the 501 contains a dot to indicate where you are in the Maximum/Minimum range. At the bottom of the left side is a micro-USB port for when the receiver is used as a computer speaker – quite a nice feature!

On the right side of the 501 you find ports for AM and FM antennas, each with a rubber traction cap, similar to what is found on the PL-990x. There is also a three position sensitivity sliding switch for Local, Normal, and DX modes – that’s one more than usually found.

Knobs on the right side are the Main tuning and Fine tuning, again similar to the PL-990x. At the very bottom of the right side is the 5v 1.0 amp micro-USB charging port.

ERGONOMICS

NEGATIVE: Here I discuss one of two major negatives with the 501. The tuning knobs are embedded quite far into the radio body. Each has a round piece of rubber covering on the knob end surface designed obviously to provide traction, possibly also as a protective measure.

The reality is that on the 501, more seriously on the PL-330, embedding of the knobs so far into the cabinet makes it virtually impossible to undertake rapid tuning using those knobs if you are just placing your finger on the top barrel part of the knob itself!

As you will see in photos and video accompanying this review, holding a finger against the rubber on the end of each knob, or closer to the center, to achieve more rapid tuning. But it’s kind of annoying. On the PL-990x the knobs are somewhat different – extending a bit farther out of the cabinet, but also with the rubber coverings.

So, this is a design point for Tecsun to consider. Surely, it should be possible to come up with slightly different knobs for the 501 that make it more comfortable to achieve rapid tuning. As it is, the knobs on the 501 barely extend beyond the cabinet edge, including the end and rubber cap.

The same goes for the PL-330 – which has knobs that only one half inch in depth, and extending only about 1/16 of an inch beyond the cabinet edge. Part of the attractiveness of the 330 is its compact size and I doubt Tecsun will be moving to put slightly larger knobs on that radio anytime soon. But as it is, using the main and fine tuning controls on the 330 gets you maybe 10 kHz in tuning range.

[UPDATE] I realized after further use of the 501x that Tecsun clearly intended for the rubber knob cap covers to act as traction for tuning. The problems I see: after significant use over time, those rubber covers will lose their stickiness and thus their ability to help tuning will be reduced. Also, the fine tuning knob is smaller — and even using the rubber cover on the knob for more traction, it is somewhat difficult to achieve rapid tuning in 1 kHz mode. Tecsun could help 501x owners on the issue with the tuning knobs by including spare rubber knob caps. But it’s uncertain how the existing rubber knob covers are attached to the original knobs and how easy it would be to replace them when they lose their stickiness.

H-501 IMPRESSIVE FRONT PANEL

At the top of the H-501 radio above the LCD display can be found the Display/Snooze/Lock button. On an older Tecsun radio, the PL-880, this button doubled as the calibration adjust control. On the PL-990x this triple function button is located on the top of the radio.

LCD DISPLAY

POSITIVE: One of the big positives of the 501 is the large LCD display. The number digits are absolutely huge and make it easy to read frequencies.

Thanks Tecsun! The display contains numerous bits of information about receiver operation, the signal strength meter, etc.

Below the display is the keypad, with special dual keys for 9/10 kHz mediumwave, Longwave activation, and FM range adjustment. Backlight activation is on the 5 key. At the bottom you have the VF/VM key to select between frequency tuning and memories. To the right are the FM, MW/LW, and SW + and – buttons. These put the radio into shortwave mode and as is the case with the PL-990 and other receivers, activate ATS/ETM tuning.

At the very bottom of the front panel can be found PLAY/PAUSE, RR, and FF buttons for control of SD card audio when using the microSD card, which like on the 990x is located on the bottom of the receiver. According to the manual, by the way, the microSD slot accepts cards of up to 128 GB. Included in the box is a 16 GB SanDisk Ultra card. A reset hole is also on the bottom of the radio.

Finally, at the bottom of the 501 face are rubber covered input ports for Earphones, Line In, and Line Out.

METAL TILT BAIL

POSITIVE AND NEGATIVE: On the back of the receiver, you find the metal tilt bail which folds down and locks into two plastic tabs and can be lifted easily with a finger from an indentation in the cabinet.

This was a good design move by Tecsun, with the following observations: there are no incremental positions on the metal bail as you find on, say, a Microsoft Surface or similar tablet type PC. The only fully stable position is to have the metal bail fully extended back. That places the 501 in a great position if you’re standing or even sitting to a degree. But if you try to place the bail in any middle position you’re in danger of having the radio become unstable. Tecsun should definitely give some thought to a re-design, though the bail is better than the flimsy plastic stands found on the PL-990 and PL-880 and some older portables.

Still on the back of the radio, intelligently, Tecsun marks a screw hole which can be used to remove the telescopic antenna (marked as ANT SCREW). The other screw holes for removal of the back of the radio are also clearly marked. Thanks Tecsun!

However, one additional partial negative – there are no rubber pads on the bottom back edge of the 501x which will be contacting whatever surface the radio is sitting on while the metal bail is in use. So, if you don’t want that bottom back edge to be scratched, place the radio on something to cushion it.

BATTERY CHARGING

POSITIVE: Another interesting feature not found on other radios: Tecsun has created a dual charging system for the 501 which uses two 18650 batteries.

In viewing numerous videos, I have not seen this discussed much. Basically, this enables you to use the receiver’s internal charging capability to choose which battery you are charging. The manual states that the battery contains space for a “spare” battery. The charging indicator on the LCD display will flash while charging is underway – there does not appear to be a separate display for battery A or B. However, and this is quite a unique capability – while you are using the 501x, the switch changes which battery the radio is using.

It’s not clear to me whether the receiver while powered on is taking energy from one or both batteries simultaneously. As I note in my reviews, and this is amplified in the manual, do not expect to be able to charge a battery internally and listen to the radio at the same time because there WILL be noise.

HUGE WORLD MAP AND RADIO DIAGRAM INCLUDED

Tecsun includes a huge – and I mean HUGE – World Amateur Radio map in a plastic pouch with the manual. On the back of this is a large photo of the 501 with clear English guide points to each and every feature of the radio. In this, Tecsun is really going out of its way to make owning the 501 a special experience.

In the box (see photos) Tecsun includes 2 18650 lithium batteries, a 5 volt double USB A charging cube, a mini to mini cord, a USB charging cable, and to boot, a pair of fairly high quality wired earphones complete with spare ear tips.

PERFORMANCE

Anon-co advises that the H-501x uses a different IC than the PL-990x. No further details were available as of the time of this writing.

This is clearly a sensitive radio, as is the PL-990X. In these days of declining use of shortwave, almost any receiver is going to be able to hear “stuff” all over the bands and the 501x and 990x as well as the 330 are all quite capable in this regard.

In the video, I tune some familiar stations, including Voice of Greece and BBC

and move through the excellent bandwidth options. This is where the 501, with its large dual speakers, excels because if you’re on a strong station – Greece is a great example because of its great music programs – and you have that wider option, it’s really pleasant to listen to.

NEGATIVE: However, one has to puzzle over the decision to limit bandwidth to 6 kHz when in shortwave mode. On mediumwave (AM) you have a 9 kHz option which provides some fine listening. Perhaps Tecsun felt that there are few stations using shortwave these days that would benefit from having a significantly wider option? I would urge Tecsun to make 9 kHz available in shortwave.

SYNCHRONOUS DETECTION

NEGATIVE: I really had some hope that Tecsun would go farther toward

solving the problem of unstable/distorted SYNC mode with all of these recent radios. Unfortunately, it was not to be.

Using SYNC on these radios – though this was not the case with the PL-660 and 680 – involves a delicate dance, requiring using a combination of bandwidth filters and LSB/USB. SYNC works fairly well with some stations, but it really depends on signal level, and to an extent signal level of any station close to the frequency you are on.

There is a 1 kHz fine tune spread when using SYNC after which lock is lost. And still, lock is often lost even when you’re on center frequency and not using

fine tune in SYNC – the signal just becomes distorted. Not fun. The PL-990x has the same issues.

Now, Tecsun has definitely made progress since the horrendous implementation of SYNC on the PL-880, which wasn’t even an official feature. But it’s disappointing that given the design features in the 501, especially the wonderful dual speakers, a way has not been found to resolve this issue which obviously involves the DSP chip that is the brain of the receiver.

Video: Detailed testing of Tecsun H-501x

ANTENNA

NEGATIVE: One of the things the folks at SONY, Panasonic and some other manufacturers did so well was design radios with antennas that nested inside the radio and could be pulled up and out of the cabinet, and because of this, there was clearance from the top of the radio so the antenna can achieve vertical position. Tecsun has not done the same. Antennas on the H-501x, PL-990x, PL-330 swivel but cannot take up vertical position, and of course they are nested on the top of the radio. One would have thought that after years of producing portables, and coming to dominate the portable market, someone at Tecsun would have recognized the importance of antenna re-design. NOTE: the antenna on the 501x is sufficiently long, but on the PL-330 for example, seems to be not long enough.

BLUETOOTH

POSITIVE: Hooray for Tecsun in integrating BT capability into the 501x and 990x. This was such an obvious move and thanks to Tecsun for really hitting it out of the park. Unfortunately, we don’t get the ability to record audio from the radio on to microSD cards – that would truly have been a major step forward

CALIBRATION

The H-501 has the same re-calibration adjustment feature as is seen in the PL-909x and the PL-330. This involves going into LSB or USB mode, holding down the USB or LSB keys until a flash appears, then using the Fine Tuning knob to achieve zero beat on WWV or strong station that is known to be on frequency, then holding down USB or LSB again to have the radio re-zero itself. This is a fine feature that we have seen since the PL-880.

When I first received the H-501 it appeared that the receiver was fairly on zero beat from mediumwave up through 25 meters shortwave. Further testing revealed that re-calibration was necessary, but the degree of error from mediumwave up through 19 meters was not as significant as I have seen on the PL-990x. Re-calibrating at a mid-point of 25 meters appears to be a good mid-point choice, but inevitably, doing re-calibration on shortwave will throw the receiver off by a bit down on mediumwave.

A cautionary note: when undertaking this calibration function be sure to give the radio time to confirm it’s in calibration mode with the FLASHing LCD. Sometimes, the readout will jump a full 1 kHz above or below the frequency you’re zeroing on – if that happens use the MAIN TUNING knob to get yourself back (i.e. 9,704 to 9,705.00) and complete the zero beat operation with the FINE TUNING knob, then hold down LSB or USB to complete.

All of this may be overkill for most people – I am just among those who obsess over having receivers as exactly on zero beat as possible. That’s more difficult or impossible to achieve with older receivers that have no calibration function, such as the ICF-2010 or SW-55 without literally taking those radios apart to access internal points of adjustment. The fact that Tecsun provides this capability in these portables is something we should all be very grateful for.

CIRCUIT LOCKUP

All of the Tecsun radios have a “reset” hole to be used if the receiver is not functioning properly. I had one occasion of lockup with this sample of the H-501x. Rather than using the reset hole, I decided to remove one of the two 18650 batteries, which of course reset the receiver. I have alerted Anon-co to this issue, but it’s hard to tell whether it’s a major problem without having other H-501 units to compare to.

CARRYING CASE

POSITIVE: The H-501 that I received for review from Anon-co came with a beautiful faux leather case complete with a convenient carrying handle. My understanding is that this matches mainland China versions that have been widely seen in videos online.

Anon-co advises that the first batch of 501x to be carried by them will come in a gift box with this PU leather case, possibly to be followed at some later point by a hardcover carrying case. Indeed, a photo can be found online showing the H-501 in a hardcover carrying case similar to the cases for the PL-880 and PL-990x kits.

As of early April, Anon-co advises that while the price for 501x is not set yet, it’s expected to be somewhere in the $310 – 330 range including shipping to the U.S.

AM/MEDIUMWAVE AND FM PERFORMANCE

Not much to say here – I find FM performance on the 501x to be superb, and mediumwave reception is more than satisfactory.

CONCLUDING THOUGHTS

As I noted earlier, these days amid declining use of shortwave by remaining broadcasters, almost any DSP or older portable receivers are capable of producing excellent results for shortwave listening.

Facebook groups devoted to shortwave (they have become the new gathering place and information exchanges for those of us who still love the hobby) are

full of newcomers inquiring about which Tecsun, Degen, or other portables are best.

Often, my advice is to consider older portables that are still quite competitive, especially considering the reduction in the number of stations still on shortwave. These would include such classics as the Grundig Satellit 700/500, the SONY

ICF-2010(2001D), SONY ICF-SW77, and ICF-SW55, along with the venerable Panasonic RF-B65 and SONY ICF-SW100S in the smaller category.

What Tecsun has done with what we have to assume may be the final group of DSP receivers it produces is come up with small (PL-330), medium (PL-990x), and large (H-501) radios that combine extremely attractive features and excellent audio. The H-501x, in effect, is a Grundig Satellit 700 re-born for the 21st century and the path to it was paved by the PL-880.

Though implementation of SYNC in each of these receivers still leaves much to be desired, having this feature is enough to push prospective buyers to choose one or more of these Tecsun units over older portables.

Note that Sangean, which is now producing its ATS-909×2 (though the radio has growing pains and is having its firmware updated by Sangean) seems to have taken note of Tecsun’s dominance of the market and provided multi-bandwith capability, and an improved and enlarged LCD display on the 909×2 along with finer frequency resolution.

In a strange but perhaps understandable decision, Sangean left SYNC mode off of its new flagship receiver. Whether this had more to do with production costs or a decision that synchronous detection really brings little to the game these days, or both, along with other factors, remains a puzzle. It does appear, from early reviews, that Sangean may have improved sensitivity on the 909×2, though this too remains unconfirmed.

But again, even with the negatives I noted here about the H-501x, what Tecsun has accomplished is significant. It has given remaining potential buyers of multi-band portables three superb receiver choices. There are others in the Tecsun line such as the S-8800 and S2000, but of these only the S8800 is something I would recommend.

As I noted in a recent review of the PL-330, had we enjoyed a situation back in the golden days of shortwave in the 1960’s/1970’s/1980’s where a portable provided multiple bandwidths, advanced memory operations, and synchronous detection, DXing would have been even more of an enjoyment than it was. Certainly those Country Heard/Country Verified totals would have been higher!

The H-501x could easily be considered the crown jewel in the Tecsun group with its killer looks, large speakers, and performance equaling the PL-990x. Each of these receivers is arguably an easy choice as a “daily driver” for traveling, though where air travel and TSA issues are concerned, the PL-330 would be a better choice.

RECOMMENDATION: Of the negatives I discuss in this article, only one I would consider fairly huge, and that is the ongoing issue with synchronous detection. If the 501x, like the 990x and 330, were to have this issue resolved that would make it easy to recommend any of the three radios. As it is, the attractiveness of the 501x lies with its beautiful two speaker design. Even with the annoying SYNC issue, I would recommend the radio to anyone who understands the SYNC issue and doesn’t mind and who wants a nice, larger version of the 909x.

The “Signal Sweeper”: How to build a portable Wellbrook loop antenna

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Many thanks to SWLing Post contributor, Matt Blaze, for the following guest post:

The “Signal Sweeper”, a portable Wellbrook antenna setup

by Matt Blaze

Here’s a very simple construction project that’s really improved my travel shortwave and mediumwave listening experience.

When I go somewhere interesting (whether a day trip on my bike or a longer excursion to an exotic locale), the two things I’m sure to want with me are my camera gear and at least one good receiver. Fortunately, there are plenty of good quality shortwave receivers to choose from these days; the hard part is packing a suitably portable antenna that can do justice to the signals wherever it is I’m going.

I’ve long had a Wellbrook antenna on my roof at home. These wide-band amplified loops famously enjoy a reputation for excellent intermod and noise rejection, as well as an almost magical ability to pull in signals comparable to much larger traditional HF and MF receive antennas. A portable Wellbrook – something I could pack in my luggage that performs as well as the one on my roof, would be just ideal.

Fortunately, Wellbrook sells a “flex” version of their antenna intended for just this application, the model FLX1530LN. It’s essentially just the amplifier of their fixed-mount antennas, equipped with a pair of BNC connectors for you to attach a user-supplied ring of coaxial cable that serves as the antenna loop. This way, you don’t need to travel with the awkwardly large 1 meter diameter ring of aluminum tubing that makes up the normal Wellbrook. You can just bring a compact spool of coaxial cable and configure a loop out of it when you arrive at your destination.

The tricky part is how to actually form a stable loop out of coaxial cable without needing lot of unwieldy supporting hardware. In particularly, I wanted something that could be set up on a camera tripod to be freestanding and easily rotated wherever I happened to find myself wanting to play radio. The key would be finding or making some kind of mostly non-metalic support for the coaxial loop that could be folded down or collapsed to fit in my baggage or backpack for travel.

And then I found it: a humble 3-section telescoping broom handle sold on Amazon for about $15 that’s exactly the right size: the “O-Cedar Easywring Spin Mop Telescopic Replacement Handle“. It collapses to 22 inches (just short enough to fit in my suitcase), and extends to 48 inches (comfortably long enough for a one meter diameter loop).

Normally, a wire loop would need both vertical and horizontal supports in a cross configuration, but by using a reasonably stiff coaxial cable, I figured I could get away with just using the broom handle vertically. I found that LMR400 (the basic kind, not the “Ultraflex” version) holds its shape quite well in a one meter loop supported this way.

At this point, it was just a matter of the details of attaching and mounting everything together into a portable package.

A one meter diameter loop, which is the ideal size for the Wellbrook amp, can be made from 3.14 meters of cable (ask your middle-school math teacher). That’s about 10 feet for Americans like me. High precision is not required here, so I just cut 10 feet of LMR400.

The next step is to attach the middle of the cable to the top of the broom handle. The O-Cedar handle has a loop at the end for hanging it on a hook in your broom closet. It happens to be just the right diameter for LMR400, but not with BNC connectors attached. So you’ll have to thread the cable through before you crimp or solder on the with connectors. (See photo above). I used the Times Microwave crimp-on BNC connectors, which I had some extras of lying around. I also put some shrink wrap on the cable at either side of the broom loop, just to keep it from slipping out and becoming unbalanced, but that was probably unnecessary.

Now I needed a way to to attach the Wellbrook amplifier to the other end of the handle, as well as some way of mounting the whole thing to a camera tripod. My first thought involved a lot of duct tape. But I wanted something more permanent and reusable.

The key is something called an “L-Plate”, which is a piece of hardware intended to allow you to mount a camera to a tripod in either “landscape” or “portrait” mode. It’s basically two tripod dovetail mounts attached at a 90 degree angle. I used one that was in my junk box, but you can buy them new or used on eBay. I also needed a clamp to attach the L-plate to the broom handle. I used the Novoflex MiniClamp 26, which I got from B&H Photo. The clamp attaches to the inside of the L-plate with a captive screw. (See photos)

Next, I attached the amplifier to the other side of the L-plate using an ordinary screw-on hose clamp. Easy enough, and surprisingly sturdy.

And that’s it. To assemble the antenna, just extend the broom handle to about one meter, allowing for a roughly one meter diameter loop that’s as round as you can make it with the amplifier at the bottom. Then clamp the L-plate to the bottom of the handle so that the handle is just above the base of the plate, and attach to the tripod. (See the photos).

The Wellbrook is powered over the feedline with a 12VDC bias-T injector. So you need a clean source of 12 volts. I use a cheap Talent Cell battery pack (available on Amazon in various capacities). These actually deliver 11.1 VDC (3x 3.7V), rather than the 12V the Wellbrook calls for, but it works fine in practice. I can also use the same pack to power the radio and digital audio recorder.

In the photos, you can see the finished antenna setup on my roof, with my permanent base Wellbrook on the rotor in the background. The performance of the two antennas is quite comparable.

(Note that there’s an eBay seller that makes a somewhat similar travel loop. The performance is quite good under normal conditions, but it is a bit more subject to MW overload when near a transmitter site. So I prefer the Wellbrook, which is much less susceptible to overload, I’ve found.)

My usual complete travel setup is either a Reuter RDR Pocket C2 radio or a Sangean ATX-909X (recently upgraded to the X2 model). Both these radios work well with the Wellbrook. I use a Sound Devices Mixpre 3 to record airchecks in the field. In the photos, I’m on a rooftop DXpedition listening to Toronto traffic and weather from CFRX on 6070 kHz on a warm later winter afternoon.

The whole setup breaks down for travel pretty easily, and fits easily in my suitcase, backpack, or bike bag (see photos). I usually bring a larger tripod than this if I’m also taking my camera.

The Wellbrook setup has really made bringing a receiver into the field a lot easier and less uncertain. There’s no worry about finding trees or other supports for wires, and packing and unpacking is quick and easy. Have fun!

Dan notes that premium receiver scammers are back on eBay

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Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post:

Premium Receiver Scammer(s) Back

by Dan Robinson

From time to time here on SWLing Post, we have alerted readers to scammers using multiple eBay addresses to attempt to rip off unsuspecting potential buyers and using old photographs of usually premium receivers to do so.

Well, whether this is one scammer or many, he is back. See the photos attached here, which show what is surely a fictitious eBay ID and what appear to be legitimate photos of a Panasonic RF-8000, one of the most sought after of the large portables from decades ago.

It’s not until the 4th photograph that this person provides that you see what’s involved in the scam, which is the scammer noting that he is “selling this on behalf of my company” and that the radio can be purchased “at the buy it now price only” The scammer then provides an email address to get around the standard eBay auction process, adding that he does not respond via Ebay messaging.

I have continued to alert eBay to these scams, and to their credit eBay has taken down many of these items in recent weeks and months, though occasionally eBay does miss these. eBay also does not make it immediately clear as to how to report items like this (HINT: you have to scroll down the page until you see a tiny REPORT link on the right side which takes you to multiple categories. These scam items fall under “LISTING PRACTICES” “FRAUDULENT LISTING ACTIVITIES” and “YOU SUSPECT THAT A LISTING IS FRAUDULENT”

If eBay has successfully already taken a scam item down, you will then see a confirmation page saying the item could not be found after refreshing the page. Very often, even after reporting an item, the identical item will show up within seconds or minutes under a completely different eBay ID (see the 2nd photo here on the Panasonic RF-8000 which shows a changed eBay ID)

Receivers most often seen on these scams include: AEG 1800A, Panasonic RF-8000, and usually other premium sets, and the tip off to the scam is that the seller/scammer usually always starts the price at $1.00 or $34.00 or similar level. In the case of the AEG 1800A, the scammer consistently uses the exact same photo of this rare receiver, from a sale that completed years ago.

I would encourage eBay users to join me in reporting scams like this — eBay certainly appreciates it and if you have eBay “Concierge” level service, which I do, it’s sometimes a help to them to get online and chat with eBay about the item and your report, especially if the eBay algorithms have failed to spot and take down a particular scam.

Thank you for sharing this, Dan. We appreciate insight from radio enthusiasts like you and Paolo. As Dan suggested, I encourage you to report listings that are obviously fraudulent to eBay. They will investigate the case and take action if it is a scam.

Guest Post: Using Carrier Sleuth to Find the Fine Details of DX

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Many thanks to SWLing Post contributor, Nick Hall-Patch, for sharing the following guest post:

Using Carrier Sleuth to Find the Fine Details of DX

by Nick Hall-Patch

Introduction

Medium wave DXers are not all technical experts, but most of us understand that the amplitude modulated signals that we listen to are defined by a strong carrier frequency, surrounded on either side by a band of mirror image sideband frequencies, containing the audio information in the broadcast.

Most DXers’ traditional experience of carriers has been in using the BFO of a receiver, using USB or LSB mode, and hearing the decreasing audio tone approaching “zero beat” of the receiver’s internal carrier compared with the DX’s carrier frequency as one tuned past it. This was often used as a way of detecting that a signal was on the channel, but otherwise wasn’t strong enough to deliver audio. Subaudible heterodynes, regular pulsations imposed on the received audio from a DX station, could indicate that there was a second station hiding there, with a slightly different carrier frequency, And, complex pulsations, or even outright low-pitched tones could indicate three or more stations potentially available on a single channel.

With the advent of software defined radio (SDR) within the last 10 years or so, the DXer has also been able to see a graphical representation of the frequency spectrum of the carrier and its associated sidebands. (Figure 1) Note that the carrier usually remains stable in amplitude and frequency, unless there are variations introduced by propagation, but that the sidebands are extremely variable.

Figure 1

Figure 2

In addition, by looking at a finer resolution of the SDR’s waterfall display, one might see additional carriers on a channel that are producing heterodynes (audible or sub-audible) in the received audio (Figure 2). Generally speaking, a DX signal with a stronger carrier will be more likely to produce readable audio, although there are exceptions to that rule.

Initially, DXers wanted to discover the exact frequency of their DX, accurate to the nearest Hertz. Although only a small group of enthusiasts were interested, they have produced a number of IRCA Reprints (https://www.ircaonline.org and click the “Free IRCA Reprints” button) over the years under the topic of “precision frequency measurement” (e.g. T-005, T-027, T-031, T-079, T-090) describing their use of some reasonably sophisticated equipment for the day, such as frequency counters.

So, why would this information be at all important? In effect, the knowledge of the exact frequency of a carrier was used to provide a fingerprint for a specific radio station. Usually, this detail was used by DXers who were trying to track down new DX, and wanted to determine whether a noisy signal was actually something that had been heard before, so would not waste any more time with it. The process of finding this exact frequency has since been made much easier by being able to view the carrier graphically in SDR software, assuming that the SDR has been calibrated before being used to listen to and record the DX. Playing back the recorded files will also contain the details of the exact frequency observed at the time of recording. And, because the exact frequency of DX has become much easier to determine using SDRs, more and more DXers seem to be using this technique.

At present, Jaguar software for Perseus is the one being used by many to determine frequency resolution down to 0.1Hz, both in receiving and in playback. But, if you have recorded SDR files from hardware other than Perseus, it is possible to get that resolution also, using software called Carrier Sleuth, from Black Cat Systems, available for both Mac and Windows, at a cost of US$20.

This software will presently take as input, sets of RF I/Q files generated by SpectraVue, SdrDx, Perseus (which includes files recorded by Jaguar), Studio One / SDRUno, Elad, SDR Console, and HDSDR. It then outputs a single file with a .fft extension, that provides the user with a set of waterfalls, similar to those displayed by SDR programs. The user decides ahead of time which frequency or set of frequencies (including all 9kHz or all 10kHz channels) will be output, and these will be displayed as individual waterfalls. one for each chosen frequency. These waterfalls can be stepped through from low frequency to high frequency, or chosen individually from a drop down menu.

Let’s start by looking at a couple of output waterfalls and work out what can be done with them, then step back to find out how to generate them, and what other data is available from them. Finally, we’ll do a quick comparison with two other programs that can produce similar output, and discuss the limitations in all three programs.

Example outputs from Carrier Sleuth

An example showing the original intent of Carrier Sleuth, determining precise carrier frequencies, is shown in Figure 3, a waterfall from 1287kHz on the morning of 28 November 2020. At 1524UT, a woman mentions “HBC” and “Hokkaido” in the original recording, so, it’s JOHR, Sapporo. Although there are a number of vertical lines representing carriers in this graphic, only one has a strong coloration, indicating at least 25dB more strength than any other carrier at the time of the ID, and about 50dB more than the background level. The absolute values of time, signal strength, and carrier frequency precise to 0.1Hz, can be found by mousing over the desired point in the waterfall and then reading the numbers in the upper right corner of the display, (encircled in Figure 3). In this case, the receiver’s reference oscillator had been locked to an accurate 10MHz clock, disciplined by GPS, so the frequency indicated in the software is not just precise, but should also be accurate. Similar accuracy could be obtainable by the traditional method of calibrating the SDR to WWV on 10 or 15MHz.

Carrier Sleuth indicates 1287.0002kHz, within 0.1Hz of that observed by a contributor to the MWoffsets list about 7 weeks earlier (https://www.mwlist.org/mwoffset.php?khz=1287). If you look closely, there is a slight wobble on the frequency, but the display is precise enough that it can indicate that, despite the wobble, JOHR does not wander away from that frequency of 1287.0002kHz.

Figure 3

But let’s face it, tracking carriers to such accuracy is a specialist interest (though admittedly, the medium wave DXing hobby is full of specialist interests, and this one is becoming more mainstream, at least among Jaguar users). However, if I played back a file from another morning, and found a strong carrier on a slightly different frequency from 1287.0002kHz, it might be an indication that some new Chinese DX was turning up, and that the recorded files would be worth a closer listen at that particular time.

Figure 4

In fact, I’ve found Carrier Sleuth to be useful in digging out long haul DX after it’s been recorded, as both trans-Arctic and trans-Pacific DX at my location in western Canada can be spotty at the best of times. This means spotty as in a “zero to zero in 60 seconds” sort of spotty, because a signal can literally fade up 10 or 15dB to a readable level in 20 seconds, perhaps with identifiable material, then disappear just as quickly. My best example so far this season was on 1593kHz, early in the UTC day of 16 November 2020, when a Romanian station on that channel paid a brief visit to my receiver in western Canada. An initial inkling of that showed up in a Carrier Sleuth waterfall, a blotch of dark red at 0358UT, and indicated by the yellow arrow in Figure 4; that caused me to go back to the recorded SDR files that had generated these traces.

The dark blotch indicates a 10dB rise and fall in signal strength including about 60 seconds of rough audio, which turned out to be the choral version of the Romanian national anthem (RCluj1593.wav). That one carrier and another one both started up at 0350UT, the listed sign-on time for Radio Cluj, which does indeed begin the broadcast day with that choral anthem. Which one of the Radio Cluj transmitters was heard is still an open question, due to the lack of carrier sleuths (computerized or otherwise) on the ground in Romania, but the more powerful one listed is a mere 15kw, so I will take either.

Finally, for those who have interest in radio propagation, the Carrier Sleuth displays can reveal some odd anomalies, for example, Figure 5 which displays both Radio Taiwan International (near 1557.000kHz on 28 November, but varies from day to day), and CNR2 (1557.004kHz) carriers as local sunrise at 1542UT approached in Victoria, BC.

Figure 5

The diffuseness of the carriers is striking, as is their tendency to shift higher in frequency at local sunrise. This doesn’t seem to be some strangeness in the original SDR recording, as there appear to be unaffected weak carriers on the channel. For comparison, Figure 3 shows the same recorded time and date, but on 1287kHz, and JOHR’s carrier is pretty stable, but there are others on that channel that show the shift higher in frequency around local sunrise. As one goes lower in frequency, these shifts became smaller and less common on each 9kHz channel, and disappear below about 1000kHz. On later mornings, however, the shifts could be found right down to the bottom of the MW band. Certainly, these observations are food for further thought.

Many of the parameters in Carrier Sleuth are adjustable by the user, for example, the sliders at the top of the screen can allow adjustment of the color palette to be more revealing of differences in signal strength. The passband shown is also easily changed, and in fact, setting the passband width to 400Hz, instead of my usual 50Hz , and creating another run of the program on 1557kHz, shows very clearly the sidebands of the “the Rumbler”, a possible jammer on the channel (Figure 6). Incidentally, a lot of the traces around 1557.000kHz in Figure 5 may well be part of “the Rumbler” signal as well, as filtering of the audio doesn’t seem to improve readability on the channel.

Although the examples here are taken from DXing overseas signals from western Canada, there is no reason why similar techniques may not be applied to domestic DXing, particularly during the daytime, when signals can be weak, but can fade up unpredictable for brief periods.

Figure 6

How to create these waterfall displays in Carrier Sleuth?

So, how can you get these displays for yourself? A “try before you buy” version of the program is available at http://blackcatsystems.com/software/medium_wave_carrier_display_app.html and both the website and the program itself contain a quite detailed set of instructions. However, the 25 cent tour can be summarized this way:

You start with a group of supported SDR data files, previously recorded, and use “Open I/Q data files” in the File drop down menu. Figure 7 shows the window that will open to allow you to choose any number of the files from your stored SDR files, by clicking the Add Files button circled in red. Then choose one of the options inside the green circle in Figure 7. They are explained in more detail in the help write up; note that the “Custom Channel” can be specified to considerably more precision than just integer kHz values, e.g. 1205.952 The rest of the settings you will probably adapt to your needs as you gain experience. Finally, set an output file name using the Set Output File button, and hit the “Process” button at the bottom of the window. There are a couple of colored bars in the upper right hand corner of the display that indicate progress, along with number of seconds left, although these are not always visible.

Figure 7

The generation of these waterfalls takes time. A computer with a faster CPU and more memory will speed things up. There is, however, an important limitation of the program. It is specified for 32-bit systems, and although it will run with no problem on 64-bit systems, individual input I/Q files are therefore restricted to 2GB or less. Many SDR users now choose to create larger files than this, and Carrier Sleuth will not handle them. Another possible limitation can occur when processing 32M FFTs, which are useful for delivering very fine frequency resolution of the carriers displayed. The program really requires in excess of 4GB of memory to handle the computation needed to deliver this fine a scale. Unfortunately, both the 2GB file size limitation and insufficient memory limitation deliver generic error messages, followed by program termination, which leaves the inexperienced user none the wiser about the true problem.

This might be a good place for a word about FFT size and Resolution Bandwidth (RBW). The FFT is a mathematical computation that takes as its input the samples of digital data that an SDR generates (or those samples that have been saved in recorded files), and generates a set of “bins”, which are individual numbers representing signal strength at a defined number of consecutive frequencies spaced across the full bandwidth being monitored by the SDR. You could think of these bins as a series of tiny consecutive RF filters, spread across the band, each delivering its own signal strength. As we are trying to look at fine scale differences in frequency when using a program like Carrier Sleuth, it is important that these little “RF filters”, or bins, each have a very narrow bandwidth. This value is called “Resolution Band Width” (RBW), and preferably should be a fraction of a Hertz to get displays such as those shown in Figures 3 through 5.

The “FFT Length” is the number of bins that the FFT display contains, and is equal to the number of I/Q samples (either from the SDR or recorded file) that are used for the input to its computation. The relationship between FFT Length, the bandwidth of the SDR or of the original recorded I/Q file, and the RBW is fairly simple:

Because the MW DXer is usually looking at data with 1MHz or more bandwidth, this equation tells us that to get a smaller than 1Hz RBW, we will need to have an FFT length of well over one million bins, so it would be wise to use an FFT length at least 8M(illion). If you are looking at a recorded file that is from an SDR using a lower bandwidth, then a lower FFT length will do the job to get a smaller RBW.

A downside of using a long FFT length is that the time resolution of the FFT becomes poorer, resulting in a display in Carrier Sleuth that will appear to be compressed from top to bottom compared with what was seen when recording the SDR file, and with correspondingly less response to fast changes in signal strength. However, using a 16M FFT Length on a recording of the MW band results in a time resolution of about 12 seconds, so it should not be a deal breaker for most.

Producing signal strength plots

A further specialist activity for some DXers is recording signal strength on specific channels, and then displaying the progress of signal strength versus time, often to indicate when openings have occurred in the past (say, at transmitter sunset), and perhaps allowing one to predict such openings in the future. But, the world has come a long way from the noting down of S-meter readings at regular time intervals, both in deriving signal strength and in plotting the results. Read on for an example.

Figure 8

Carrier Sleuth recently added the capability of creating files containing signal strength versus time for specified frequencies, and, depending on the size of RBW, to deliver that signal strength as observed in a passband as narrow as 0.05Hz, or as wide as 10Hz. The program extracts the signal strength information from one of the FFT files that it has already generated from a selection of SDR I/Q files. In Figure 5, two stations’ signals, from Radio Taiwan International, and from CNR2, were featured in the display. With roughly 4Hz difference between the two signals, it is easily possible with Carrier Sleuth to derive signal strength from each one, specifying a bandwidth of, say 1.2Hz, to account for the propagation induced drifts and smearing of the carriers, not to mention any drift in either the receiver or transmitter.

The program creates a .csv file (text with comma delimiters) of signal strength versus time for all the frequencies chosen from an individual FFT file, but does not plot them. There are several programs that can create plots from CSV files For example, an Excel plot generated from Figure 5 is in Figure 8, showing peaks in those signals that occurred both before and after local sunrise at 15:42UTC. Note that the user is not restricted to the signals found on just one of the waterfalls that are found in the FFT file, but can pick and choose dozens of signals found anywhere in those waterfalls. (Note also that one can choose locations on any waterfall where there is no signal trace, in order to provide a “background level versus time” in the finished plots, if desired)

The process used to generate this CSV file involves searching through the FFT waterfalls for signal traces that are likely candidates for adding to such a file. On the first candidate found, the user right clicks the mouse on the trace, at the exact frequency desired; this will bring up an editable window. The window will show the chosen frequency as well as any subsequent ones that will be chosen, then the overall selection is saved to a text file after editing, so that the user can move on to generating the CSV file.

That file is created by going to the File drop down menu, and choosing “Generate CSV File”, where the text file produced earlier can be chosen. Once that file is selected, the CSV file is immediately generated, and can then be manipulated separately as the user chooses.

Are there comparable programs?

Displaying waterfalls in SDR programs playing back their own files is nothing new, though not that many can do it at as fine a scale as Carrier Sleuth does, and most programs are not optimized to handle such a variety of input I/Q files.

One that does read a fair number of different kinds of SDR files is the SDR Console program; this includes Data File Analyser (64-bit only) which also can display carrier tracks to a high resolution, so let’s take a quick look at what Analyser does. If you are familiar with SDR Console, and are reasonably experienced with the way it handles your SDR or plays back files from your favored SDR software, then these online instructions https://www.sdr-radio.com/analyser will help you get started with Analyser

This program will input a group of SDR files, then display an equivalent to a single one of the waterfalls output by Carrier Sleuth, displaying the carrier traces in reverse order, with time running from bottom to top of the display. Figure 9 shows the equivalent of Carrier Sleuth’s display of the 1287kHz carrier traces shown in Figure 3. Analyser has a convenient sliding cross hair arrangement (shown in the yellow oval) to reveal time and frequency at any point in the display, but the actual signal power available at that point must be derived from the rough RGB scale along the left hand border. Analyser is apparently capable of about 0.02Hz resolution when reading from full bandwidth medium wave SDR files, but the default is to display exact frequency only to the nearest Hertz. The “Crosshairs” ribbon item has a drop down of “High-Resolution” which displays to the nearest milliHertz however, though that will be limited by the actual RBW of the generated display. The graphic display can be saved as a project after the initial generation of the signal traces, which allows the user to return to the display without having to generate it all over again, equivalent to opening one of Carrier Sleuth’s FFT files.

A useful facility in Analyser is the ability to click “Start” in the Playback segment of the ribbon above an Analyser display, then mouse over and click on a signal trace; this action will play back the audio for that channel in SDR Console, at that point in time.

It is possible to generate a signal strength plot of signal strength versus time for any individual frequency in the waterfall display, and to save that plot as a CSV file (“Signal History”). But, the signal strength is that found only in a +/- 0.5Hz passband around the chosen frequency, with no other possibilities. If you want to generate a plot for another frequency on the same waterfall, then you will need to run the process again, and if you want a plot for another frequency in the SDR files, then you need to generate another waterfall, which, depending on your computer’s capability, could take some time. On an i3 CPU-based netbook with 4GB of memory, it took 30 minutes to produce one frequency’s worth of traces from data files scanning three hours. On the same machine, Carrier Sleuth could deliver all 9kHz channels in 1hr20min from the 3 hours of files. However, it also took 1hr20min to play back just one channel in Carrier Sleuth, which is not so efficient. (further note: Nils Schiffhauer has developed a technique to speed up Data Analyser processing, by first using Console’s Data File Editor on full bandwidth MW recorded files; details will likely appear at https://dk8ok.org)

To conclude then, SDR Console’s Analyser will produce a display of a single channel faster than Carrier Sleuth will, and will play back the audio associated with that channel, while also having the capability to plot and record signal strength for a single given frequency within that display, but only on 64-bit computers. It can also handle SDR files larger than 2GB in size, and will run more quickly if a NVIDIA graphics card has been installed. Analyser is also strict about sequence of files. If there is the slightest gap between one file finishing, and the next file starting in time sequence, it regards that as a new set, that will need to be processed separately.

Where Carrier Sleuth is more useful is that once an FFT file has been generated, it is easy to quickly check multiple channels for interesting openings during the recorded time period. It can also provide very precise frequencies of carriers, and is able to generate a file of signal strengths versus time from multiple frequencies, including those frequencies that are separated by barely more than the RBW. For the MW band, that can be near 0.1Hz, often beyond the capability of transmitters to be that stable. See Figure 10, which shows signal strength traces from JOCB and HLQH both on 558kHz, and separated in frequency by 0.1Hz. At 1324UTC, JOCR dominates with men in Japanese, and at 1356UTC, the familiar woman in Korean dominates, indicating HLQH.

Figure 9

Figure 10

Incidentally, another program that seems to offer a similar functionality to Carrier Sleuth and SDR Console’s Analyser is, of course, Jaguar, which has made a point of displaying 0.1Hz readout resolution when using the Perseus SDR, and in playing back Perseus files, but…only Perseus. There is a capability called Hi-Res in Jaguar Pro that can be applied when playing back files; this also displays fine scale traces of frequency versus the passage of time. Steve VE6WZ, sent the example shown in Figure 11, zeroing in on his logging of DZAR-1026. As with Analyser, clicking on a certain point in the display plays back the audio at that time, but it is unclear at this point whether the display can be saved, or whether it is generated only for one individual channel, and then is lost.

Figure 11

+ + + + + + + + + + + +

Availability

Carrier Sleuth http://blackcatsystems.com/software/medium_wave_carrier_display_app.html

Analyser (SDR Console) https://www.sdr-radio.com/download

Jaguar http://jaguars.kapsi.fi/download/ (these are the Lite versions; to unlock the Pro version, purchase is needed)

(this article first appeared in International Radio Club of America’s DX Monitor)

Many thanks, Nick. This is amazing. What a brilliant tool to find nuances of a DX signal. I can’t help but marvel at the applications we enthusiasts have available today. Thank you for sharing!

Rob compares horizontal and vertical SWL random wire antennas

6 Replies

Many thanks to SWLing Post contributor, Rob Zingarelli, who shares the following guest post that originally appeared on his blog in October, 2020:

Shortwave Antenna: Vertical or Horizontal?

by Rob Zingarelli

This is a question that has circled around on the fringes of my consciousness for years now, but one that I’ve never quite found time to test. And it is a simple question: When using a random wire antenna with a portable shortwave receiver, is it better to string the wire vertically or horizontally, or does it even matter? Mostly this is a question when out camping, because arranging a 19′ wire vertically is usually a good bit more involved than just stringing it out along some nearby bushes.

Before going any farther, I want to point out that this is an exercise in ordinary backyard shortwave listening with relatively inexpensive equipment. There are many, many better-engineered and more costly solutions to the technical challenge of shortwave scanning, and this does not address any of those sophisticated approaches. This is for the person who opens up the box and wonders about the best way to hang the included long-wire auxiliary antenna.

Equipment: Tecsun PL-660 SW/AM/FM/Air Band receiver, with its included 19′ random-wire antenna. Internal battery power used.

Conditions & Time: Clear local weather. hamqsl.com’s nowcast of band conditions were fair from 3.5-14.35 MHz, and poor for higher frequencies, with SFI = 72, SN = 26, A = 5, K = 1. Time was 21:00-21:30 UTC, or 4-4:30 pm local CDT.

Procedure: Out in the backyard (typical residential neighborhood, well-spaced ~150′ between houses, above-ground power lines 125′ away), suspend random wire from ground to its full length. This was achieved using a length of paracord over a tree limb, with the tree trunk ~30′ from the radio’s location. With the PL-660’s antenna gain control set to “Normal” (i.e., the mid-setting of Local-Normal-DX) and the bandwidth set to narrow, use the receiver’s automatic scan function to see how many stations were received. Make notes of the number of transmissions detected, reception characteristics and quality, and any perceived noise levels. Re-orient the antenna to a low horizontal position, over two sawhorses approximately 3′ high (see picture), and repeat.

Sawhorses spaced ~17′ apart. Radio and notepad can be seen on ground in front of the near sawhorse.

Results: For the vertical antenna orientation, 32 stations were detected between 5959 – 15730 kHz. Nearly all were intelligible, with those at the lower end more steady and those a the higher end much more variable in strength. For the horizontal antenna orientation, 21 stations were detected between 9265 – 1570 kHz. Similar overall signal quality was heard for the received stations in either antenna orientation. More noise was noticeable at the lower frequencies between the stations for the vertical antenna orientation. However, this was significantly below the received signal levels, and not an issue in the overall listening quality.

Conclusions & Discussion: Suspending the wire antenna vertically worked better, especially at the lower frequencies. Getting a wire up 21’+ vertically is usually not as convenient as stringing it horizontally, but it may be worth the extra effort, depending on the location, campsite, nearby trees, etc. The overall conditions were typical for fall camping weather, with fair-to poor radio propagation conditions, so this result should be broadly applicable for how SW portables are often used. This result may change with propagation and radio noise conditions, both for atmospheric and local noise sources. Testing will continue as propagation conditions improve with solar cycle 25 getting underway.

——-

Addendum, 10/12/20: While writing this up yesterday evening, it occurred to me that I hadn’t tested the PL-660’s built-in whip antenna. This comparison is important, because sometimes the wire antenna is too cumbersome to deploy. So, how does the whip antenna compare?

Conditions & Time: Overall, very similar to yesterday. hamqsl.com reports fair conditions from 3.5–14.35 MHz, and poor for higher frequencies. SFI = 72, SN = 26, A = 3, K = 1. Same time of day as yesterday’s testing.

Procedure: Repeat of yesterday, with the whip antenna added to the test. The whip was oriented vertically.

Results: For the vertical 19′ wire, 31 stations were found by the auto-scan function between 2380 – 15770 kHZ. Electrical noise was low but audible in the 3 MHz region, fading to none at higher frequencies, and not a significant source of interference with any stations. For the horizontal wire, 15 stations were found between 9265 – 13630 kHz. Electrical noise was barely audible. With the whip in use only 1 station was found. Switching the antenna gain to its DX (most sensitive) setting, 6 stations were found.

Revised Conclusions: Adding to yesterday’s conclusions, the whip antenna functioned but was vastly inferior to the wire antenna in either configuration, even with the gain set to DX. Today’s results with the wire antenna were, unsurprisingly, very similar to yesterday’s, given that the ionospheric and weather conditions were nearly identical. Noise was not a factor in receiving for any of these antennas or configurations, but did noticeably increase for the vertical wire antenna.

Thank you for sharing this, Rob! It’s experiments like this that help us determine, especially, what antenna setups work at our own particular locations since RFI characteristics can vary so much. I’m guessing had your horizontal wire been elevated to even 20′ off the ground it might have produced better results, but sometimes this can be difficult to achieve. I like how you used the auto search function to determine the number of stations you could receive with each setup and it was a great addition to include the built-in telescoping whip.

Thank you again for sharing your results with us!

Loop-On-Ground Antenna Part 2: Tom upgrades his low profile, low noise, portable DXing antenna

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

Loop on Ground Part 2

by TomL

My previous Loop on Ground (LoG) experiment was useful which entailed connecting my Wellbrook loop amplifier to a 100 foot loop of speaker wire in the field at my favorite local Forest Preserve. It really brought in stations I had never heard before or strong stations in a more powerful way that made the audio really pleasant to listen to. This report will describe more experiments with smaller wire loops to see what the limitations are. 100 feet of wire is quite a lot of wire to mess around with especially in the cold weather or public places that do not have as much private space.

I don’t understand all the electrical interrelationships but a long posting at RadioReference.com had a great discussion about creating a 160-20 meters LoG receive-only antenna. It is 11 pages long but is worth reading how “nanZor” experimented with various parameters for general use. Kudos to him for documenting the findings as the design changed over time. You can find it here:

https://forums.radioreference.com/threads/160-20m-log-loop-on-ground.370110/

nanZor basically boils it down to a few guidelines.

Keep it on the ground. Lifting the wire more than an inch or two decreased the lower angle signal reception greatly.
Calculate the optimal length for one full wavelength of wire at the highest target frequency, say for example, the top of the 20 meter band (14350 kHz). 936/14.350 MHz * 0.9 velocity factor of simple insulated wire = 58.7 feet. You can round up to 60 feet, no big deal since this is broadband. The antenna should have a predictable reception pattern from 1/10th wavelength up to 1 full wavelength. Outside that range, the pattern gets “squirrely”.
Using a 9:1 balun seemed to be a little better than a 4:1 balun at the antenna feedpoint. This gets into things I cannot measure and has to do with rising impedance as a loop gets closer to ground level. I am not sure but I think my Wellbrook amp has a built in 4:1 balun and it seems to work just fine.
Make sure to use an RF Choke at BOTH sides of the feedline coax cable. He was adamant that the loop can get easily unbalanced and allow noise into the antenna and/or feedline and so it must be isolated and the ground allowed to “float” in his words.

Personally, I also wanted to use less wire and happened to have a length of 42 feet of landscape wire which should work well below 5 MHz with the Wellbrook amp engaged. Results were not bad even though on hard frozen ground. Signal levels were down a little compared to the 100 foot of wire. Here are a couple of examples, first one in a fast food parking lot with a grass field next to it and second at the usual Forest Preserve parking lot on a grass field. I made sure that my car blocked the view of the wire so people would not get nervous!

La Voz Missionaria, Brazil:

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Voice of Welt from Issoudun France in Kurdish:

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These are not necessarily “DX” but definitely good for SWLing. I like the signal strength with the amplifier inline at the antenna feedpoint and I did not have to use an RF Choke at the receiver side as was suggested.

I had a 75 foot long insulated wire and used that at the Forest Preserve parking lot on a couple of different days. Lower frequency signal strength and signal/noise ratio improved a little bit to be noticeable.

US Air Force HFGCS “numbers” station. Remote controlled from Andrews or Grand Forks bases (https://en.wikipedia.org/wiki/High_Frequency_Global_Communications_System), there was no way for me to know which of the 6 transmitters it was coming from:

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BBC from Tinang Philippines in Korean:

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Then, as nanZor suggested in his postings, I purchased a 9:1 balun/RF choke (it has both a balun and an RF choke built-in) from Ham Radio Outlet and put that in place of the Wellbrook amplifier.

I have not worked with it, but it is reported that the Nooelec.com v2 model is cheaper and works just as well – https://swling.com/blog/2019/10/the-nooelec-balun-19-v2/

Examples below with the 42 foot loop and 9:1 balun/choke, no amplifier:

KSDA, Agat Guam in English

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WB8U doing a POTA activation of Leavenworth State Fishing Lake

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VOLMET weather, Shannon Ireland

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HCJB Quito Ecuador, probably in Quechua

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As a side note, there is a posting that mentions low-angle DX is better with regions that have better “ground conductivity”, salt water being the best. I have no way of verifying this. See post# 126 by KK5JY Matt.

So, bottom line is that a Loop on Ground can be useful for pleasant SWLing and portable. Best to use it on grass, not asphalt. The loop amplifier is useful to get signal levels up if you have to use a smaller loop size but the signal/noise ratio will suffer due to its smaller aperture. And, warning, the public will find a way to trip over the wire no matter where you set it up (I may try putting the wire around my car if I can park on a grass surface and/or use the gaudiest, brightest neon green or orange wire I can find – they can’t trip over THAT, can they?).

TomL

Thanks, Tom, for sharing your update. Obviously, the LoG is working brilliantly. It’s amazing that you got such clear reception from the parking lot of a fast food restaurant. If you were using a vertical instead, I bet signals would have been buried in the noise.

I can also relate to people tripping over antenna wires. I remember one POTA activation recently (the first activation in this three park run) where I intentionally laid my counterpoise on the ground, off a foot path, in the brush and where I couldn’t imagine anyone ever stepping. Ten minutes into the activation and for no reason, someone walked off the path, into the brush, and it snagged them. Maybe I’m just a Ninja level trapper and never realized it!?

Thanks again for sharing the results of your LoG, Tom. Inspiring!

Tom builds a portable Loop-On-Ground antenna

11 Replies

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

My First Loop-On-Ground antenna

A number of people have mentioned the Loop On Ground (LOG) antenna in the past as a good receive-only antenna. I did some research but could only find a few examples by amateur radio operators.

Matt Roberts (KK5JY) has a good article including some antenna theory and measurements, you can find it here:

http://www.kk5jy.net/LoG/

Someone named Tom (KG3V) has a write up on it but it is a little short on details:

https://kg3v.com/2020/01/04/loop-on-ground-the-simplest-receive-antenna-you-will-ever-build-and-it-works/

Stana Horzepa (WA1LOU) has something similar:

https://tapr.org/loop-on-ground-log-antenna/

I also read somewhere that for transmitting, a LOG antenna is useless as it radiates much of the energy right into the ground! But I didn’t care about that. I needed something for receive I can deploy easily without supports and take down just as easily. As you may recall, my home condo is literally saturated with noise and I cannot null it out. So a wire looped on the ground is supposed to work? You bet it does!

Of course, there are some conditions to meet. There has to be enough flat ground away from people or pets (or lawn mowers!) who would get tangled in the wire on the ground. The wire should be as close to the ground as possible (although I had good results laying the wire on top of cut grass). The loop of wire can vary in circumference from about 20 feet to 150 feet (the shorter length will stay in an omnidirectional pattern higher in frequency but lower in signal pickup and vice-versa for the longer length). The wire needs to be insulated. That’s about it!

So, off to the hardware store to buy a cheap spool of 100 foot 18 gauge speaker wire. But, the articles mention using a balun and they all made their own. I did not feel like doing that (I am not that good at making things from scratch) and I did not want to spend money ordering one. More reading somewhere informed me that my existing Wellbrook Medium Aperture loop amplifier has a built-in balun at the antenna side of the device. Hallelujah!

I bundled together the wire, Wellbrook parts and battery supply, small laptop and Airspy HF+ to my favorite Lake Nelson Forest Preserve. The shelter there is little used and is adjacent to the prairie with cut grass. It did take a good 15 minutes to lay out the 100 feet of wire on the ground while trying to keep it as flat as possible. And I did not have enough space for a circle, so I ended up with an oblong shape. The long sides are facing directly north-south, so in theory (I think) this gives me an oblong shaped reception pattern east-west. The photo shows half of the wire laying on the grass.

I ended up with this setup on a picnic table at the rear end of the shelter. The coax wire goes from the Wellbrook amp into its power module, then to a Cross Country Wireless preselector, then to the Apirspy HF+ and laptop.

I was really impressed by the signal strength of the usual suspects like Radio Nacional da Amazonia. I could see that the Wellbrook amp was boosting signals across the board with only a little extra noise.

I use the preselector to try to keep the Airspy radio from overloading, especially mediumwave broadcast signals which can sound like a small amount of extra “hash” type noise in the background. I have since added into the accessory chain an old Kiwa Electronics BCB filter that does a great job of knocking down the frequencies below 2 MHz.

I have also since added a water resistant box to enclose the Wellbrook amp to keep it safe from getting stepped on or too wet.

Also, a couple of weeks later I was able to go to a campgound and try out 60 feet of wire but the result was noisier since I was surrounded by RV vehicles in a crowded campsite. It was not horrible and I was able to listen to some good radio stations but location can matter with any antenna.

I hope you like the recordings below. Because of some serious health issues this summer, these May 31 2020 recordings & report are just being published now (I am recovering slowly but surely!). My small laptop is under-powered, so I was only able to record MP3 files one at a time. It kept me busy as I went from one frequency to the next and kept recording anything I heard. I was able to hear a couple of stations I never heard before and that is a success in my book.

It remains to be seen if this antenna is as good as my 19 foot vertical antenna attached to the top of the car roof, especially low-angle DX signals. Maybe you will have the chance to experiment as well and share your experience, too. Now, will a small loop-on-ground antenna around my car parked late at night at a far corner of the grocery store work OK??? I will have to try it!

Recordings (crank up the volume if it is too weak):

22:00 UTC, Radio Saudi (Arabic) 11915 kHz

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