Tag Archives: Longwave

Guest Post: Why does radio reception improve on saltwater coasts?

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


Gone fishing…for DX: Reception enhancement at the seaside

by 13dka

In each of my few reviews I referred to “the dike” or “my happy place”, which is a tiny stretch of the 380 miles of dike protecting Germany’s North Sea coast. This is the place where I like to go for maximum listening pleasure and of course for testing radios. Everyone knows that close proximity to an ocean is good for radio reception…but why is that? Is there a way to quantify “good”?

Of course there is, this has been documented before, there is probably lots of literature about it and old papers like this one (click here to download PDF). A complete answer to the question has at least two parts:

1. Less QRM

It may be obvious, but civilization and therefore QRM sources at such a place extend to one hemisphere only, because the other one is covered with ocean for 100s, if not 1000s of miles. There are few places on the planet that offer such a lack of civilization in such a big area, while still being accessible, habitable and in range for pizza delivery. Unless you’re in the midst of a noisy tourist trap town, QRM will be low. Still, you may have to find a good spot away from all tourist attractions and industry for absolutely minimal QRM.

My dike listening post is far enough from the next small tourist trap town (in which I live) and also sufficiently far away from the few houses of the next tiny village and it’s located in an area that doesn’t have HV power lines (important for MW and LW reception!) or industrial areas, other small villages are miles away and miles apart, the next town is 20 km/12 miles away from there. In other words, man-made noise is just not an issue there.

That alone would be making shortwave reception as good as it gets and it gives me an opportunity to check out radios on my own terms: The only way to assess a radio’s properties and qualities without or beyond test equipment is under ideal conditions, particularly for everything that has to do with sensitivity. It’s already difficult without QRM (because natural noise (QRN) can easily be higher than the receiver’s sensitivity threshold too, depending on a number of factors), and even small amounts of QRM on top make that assessment increasingly impossible. This is particularly true for portables, which often can’t be fully isolated from local noise sources for a couple of reasons.

Yes, most modern radios are all very sensitive and equal to the degree that it doesn’t make a difference in 98% of all regular reception scenarios but my experience at the dike is that there are still differences, and the difference between my least sensitive and my most sensitive portable is not at all negligible, even more because they are not only receivers but the entire receiving system including the antenna. You won’t notice that difference in the middle of a city, but you may notice it in the woods.

When the radio gets boring, I can still have fun with the swing and the slide!

2. More signal

I always had a feeling that signals actually increase at the dike and that made me curious enough to actually test this by having a receiver tuned to some station in the car, then driving away from the dike and back. Until recently it didn’t come to me to document or even quantify this difference though. When I was once again googling for simple answers to the question what the reason might be, I stumbled upon this video: Callum (M0MCX) demonstrating the true reason for this in MMANA (an antenna modeling software) on his “DX Commander” channel:

To summarize this, Callum explains how a pretty dramatic difference in ground conductivity near the sea (click here to download PDF) leads to an increase in antenna gain, or more precisely a decrease in ground return losses equaling more antenna gain. Of course I assumed that the salt water has something to do with but I had no idea how much: For example, average ground has a conductivity of 0.005 Siemens per meter, salt water is averaging at 5.0 S/m, that’s a factor of 1,000 (!) and that leads to roughly 10dB of gain. That’s right, whatever antenna you use at home in the backcountry would get a free 10dB gain increase by the sea, antennas with actual dBd or dBi gain have even more gain there.

That this has a nice impact on your transmitting signal should be obvious if you’re a ham, if not just imagine that you’d need a 10x more powerful amplifier or an array of wires or verticals or a full-size Yagi to get that kind of gain by directionality. But this is also great for reception: You may argue that 10dB is “only” little more than 1.5 S-units but 1.5 S-units at the bottom of the meter scale spans the entire range between “can’t hear a thing” and “fully copy”!

A practical test

It’s not that I don’t believe DX Commander’s assessment there but I just had to see it myself and find a way to share that with you. A difficulty was finding a station that has A) a stable signal but is B) not really local, C) on shortwave, D) always on air and E) propagation must be across water or at least along the shoreline.

The army (or navy) to the rescue! After several days of observing STANAG stations for their variation in signal on different times of the day, I picked one on 4083 kHz (thanks to whoever pays taxes to keep that thing blasting the band day and night!). I don’t know where exactly (my KiwiSDR-assisted guess is the English channel region) that station is, but it’s always in the same narrow range of levels around S9 here at home, there’s usually the same little QSB on the signal, and the signals are the same day or night.

On top of that, I had a look at geological maps of my part of the country to find out how far I should drive into the backcountry to find conditions that are really different from the coast. Where I live, former sea ground and marsh land is forming a pretty wide strip of moist, fertile soil with above average conductivity, but approximately 20km/12mi to the east the ground changes to a composition typical for the terminal moraine inland formed in the ice age. So I picked a quiet place 25km east of my QTH to measure the level of that STANAG station and also to record the BBC on 198 kHz. Some source stated that the coastal enhancement effect can be observed within 10 lambda distance to the shoreline, that would be 730m for the 4 MHz STANAG station and 15km for the BBC, so 25km should suffice to rule out any residue enhancement from the seaside.

My car stereo has no S-meter (or a proper antenna, so reception is needlessly bad but this is good in this case) so all you get is the difference in audio. The car had the same orientation (nose pointing to the east) at both places. For the 4 MHz signal though (coincidence or not), the meter shows ~10dBm (or dBµV/EMF) more signal at the dike.

3. Effect on SNR

Remember, more signal alone does not equal better reception, what we’re looking for is a better signal-to-noise ratio (SNR). Now that we’ve established that the man-made noise should be as low as possible at “my” dike, the remaining question is: Does this signal enhancement have an effect on SNR as well? Even if there is virtually no local QRM at my “happy place” – there is still natural noise (QRN) and that wouldn’t that likely gain 10dB too?

Here are some hypotheses that may be subject of debate and some calculations way over my head (physics/math fans, please comment and help someone out who always got an F in math!). Sorry for all the gross oversimplifications:

Extremely lossy antennas

We know that pure reception antennas are often a bit different in that the general reciprocity rule has comparatively little meaning, many antennas designed for optimizing reception in specific situations would be terrible transmitting antennas. One quite extreme example, not meant to optimize anything but portability is the telescopic whip on shortwaves >10m. At the dike, those gain more signal too. When the QRN drops after sunset on higher frequencies, the extremely lossy whip might be an exception because the signal coming out of it is so small that it’s much closer to the receiver noise, so this friendly signal boost could lift very faint signals above the receiver noise more than the QRN, which in turn could mean a little increase in SNR, and as we know even a little increase in SNR can go a long way.

The BBC Radio 4 longwave recording is likely another example for this – the unusually weak signal is coming from a small and badly matched rubber antenna with abysmal performance on all frequency ranges including LW. The SNR is obviously increasing at the dike because the signal gets lifted more above the base noise of the receiving system, while the atmospheric noise component is likely still far below that threshold. Many deliberately lossy antenna design, such as flag/tennant, passive small aperture loops (like e.g. the YouLoop) or loop-on-ground antennas may benefit most from losses decreasing by 10dB.

Not so lossy antennas, polarization and elevation patterns

However, there is still more than a signal strength difference between “big” antennas and the whips at the dike: Not only at the sea, directionality will have an impact on QRN levels, a bidirectional antenna may already decrease QRN and hence increase SNR further, an unidirectional antenna even more, that’s one reason why proper Beverage antennas for example work wonders particularly on noisy low frequencies at night (but this is actually a bad example because Beverage antennas are said to work best on lossy ground).

Also, directional or not, the “ideal” ground will likely change the radiation pattern, namely the elevation angles, putting the “focus” of the antenna from near to far – or vice versa: As far as my research went, antennas with horizontal polarization are not ideal in this regard as they benefit much less from the “mirror effect” and a relatively low antenna height may be more disadvantageous for DX (but maybe good for NVIS/local ragchewing) than usual. Well, that explains why I never got particularly good results with horizontal dipoles at the dike!

Using a loop-on-ground antenna at a place without QRM may sound ridiculously out of place at first, but they are bidirectional and vertically polarized antennas, so the high ground conductivity theoretically flattens the take-off angle of the lobes, on top of that they are ~10dB less lossy at the dike, making even a LoG act more like something you’d string up as high as possible elsewhere. They are incredibly convenient, particularly on beaches where natural antenna supports may be non-existent and I found them working extremely well at the dike, now I think I know why. In particular the preamplified version I tried proved to be good enough to receive 4 continents on 20m and a 5th one on 40m – over the course of 4 hours on an evening when conditions were at best slightly above average. Though the really important point is that it increased the SNR further, despite the QRN still showing up on the little Belka’s meter when I connected the whip for comparison (alas not shown in the video).

The 5th continent is missing in this video because the signals from South Africa were not great anymore that late in the evening, but a recording exists.

Here’s a video I shot last year, comparing the same LoG with the whip on my Tecsun S-8800 on 25m (Radio Marti 11930 kHz):

At the same time, I recorded the station with the next decent KiwiSDR in my area:

Of course, these directionality vs noise mechanisms are basically the same on any soil. But compensating ground losses and getting flat elevation patterns may require great efforts, like extensive radial systems, buried meshes etc. and it’s pretty hard to cover enough area around the antenna (minimum 1/2 wavelength, ideally more!) to get optimum results on disadvantaged soils, while still never reaching the beach conditions. You may have to invest a lot of labor and/or money to overcome such geological hardships, while the beach gives you all that for free.

But there may be yet another contributing factor: The gain pattern is likely not symmetrical – signals (and QRN) coming from the land side will likely not benefit the same way from the enhancement, which tapers off quickly (10 wavelengths) on the land side of the dike and regular “cross-country” conditions take place in that direction, while salt water stretching far beyond the horizon is enhancing reception to the other side.

So my preliminary answer to that question would be: “Yes, under circumstances the shoreline signal increase and ground properties can improve SNR further, that improvement can be harvested easily with vertically polarized antennas”.

Would it be worthwhile driving 1000 miles to the next ocean beach… for SWLing?

Maybe not every week–? Seriously, it depends.

Sure, an ocean shoreline will generally help turning up the very best your radios and antennas can deliver, I think the only way to top this would be adding a sensible amount of elevation, a.k.a. cliff coasts.

If you’re interested in extreme DX or just in the technical performance aspect, if you want to experience what your stuff is capable of or if you don’t want to put a lot of effort into setting up antennas, you should definitely find a quiet place at the ocean, particularly if your options to get maximum performance are rather limited (space constraints, QRM, HOA restrictions, you name it) at home.

If you’re a BCL/program listener and more interested in the “content” than the way it came to you, if you’re generally happy with reception of your favorite programs or if you simply have some very well working setup at home, there’s likely not much the beach could offer you in terms of radio. But the seaside has much more to offer than fatter shortwaves of course.

From left to right: Starry sky capture with cellphone cam, nocticlucent clouds behind the dike, car with hot coffee inside and a shortwave portable suction-cupped to the side window – nights at the dike are usually cold but sometimes just beautiful. (Click to enlarge.)

However, getting away from the QRM means everything for a better SNR and best reception. In other words, if the next ocean is really a hassle to reach, it may be a better idea to just find a very quiet place nearby and maybe putting up some more substantial antenna than driving 1000 miles. But if you happen to plan on some seaside vacation, make absolutely sure you bring two radios (because it may break your heart if your only radio fails)!

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Best portable radio for LW and NDB reception?

Many thanks to SWLing Post reader, Ian Harling (G7HFS), who writes:

I have been a SWL for about 50 yrs and also hold an amateur radio license, but here is where I need some advice.

Can you recommend a portable radio that performs well longwave and also NDB reception? I do have a Datong VLF converter that I can use but I’m looking for a dedicated portable set that works well on frequencies between 100 and 500 kHz. Any suggestions?

Good question, Ian. While I always do a basic check of longwave performance on shortwave portables–checking regional NDBs–I have never done a proper comparison test or used them for longwave listening or DXing sessions.

I know there are some dedicated LW DXers and listeners in the SWLing Post community, so my hope is someone can chime in with their radio suggestion in the comments section. Thank you in advance!

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Europe 1 to close 183 kHz longwave service December 31, 2019

Transmitter building of Europe 1 with one of the radio masts in the background (Source: Wikimedia Commons)

Many thanks to SWLing Post contributor, Gaétan Teyssonneau, who notes that Europe 1 has announced that they will close their 183 kHz longwave service on December 31, 2019 at midnight. Gaétan shared the following message, in French, from Europe 1:

Cher Monsieur.
Les habitudes d’écoute étant en train d’évoluer et l’utilisation des supports numérique se multipliant, Europe 1 n’émettra plus en grandes ondes à partir du 31 décembre 2019 minuit.

Un choix assumé par la station qui a toujours fait preuve d’innovation dans sa manière de penser et concevoir l’écoute de ses programmes. l’approche environnementale a également motivé cette décision. Quitter les grandes ondes c’est aussi protéger l’environnement.

Bonnes fêtes à vous .

Constance BENQUÉ

Directrice Générale Lagardère News (Europe 1/ Paris Match / JDD)

CEO ELLE International

Thanks again for sharing this news, Gaétan.

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WI2XLQ: Brian Justin’s annual longwave broadcast

Canadian Reginald Aubrey Fessenden in his lab believed circa 1906 (Source: Radio Canada International)

(Source: ARRL News via Harald Kuhl)

The Canadian inventor, experimenter, and entrepreneur Reginald Fessenden has been credited as the inventor of radiotelephony. Fessenden claimed to have made his first voice — and music — broadcast on Christmas Eve in 1906 from Brant Rock, Massachusetts, although his account is disputed. As he has done each December for the past few years, Brian Justin, WA1ZMS, of Forest, Virginia, will transmit a program on 486 kHz, under authority of his FCC Part 5 Experimental License WI2XLQ ito commemorate Fessenden’s accomplishments.

Justin will transmit for at least 24 hours starting at around 2000 UTC on December 24, with a repeat transmission on New Year’s Eve likely, “keeping in step with what Fessenden was reported to have done on both nights in 1906,” Justin explained.Fessenden’s transmitter was most likely a high-speed “dynamo” or alternator — a predecessor to the later Alexanderson alternator — modulated by placing a carbon microphone in series with the antenna feed line to create an amplitude modulated signal. Fessenden a few years earlier had limited success making voice transmissions using a rotary spark gap transmitter. Fessenden fed his signal into a substantial antenna system erected in Brant Rock for his experiments. Accounts say on Christmas Eve 1906, he transmitted recordings of two pieces of music and read a verse from the bible.

Justin will use somewhat more modern equipment — a home-brew master oscillator, power amplifier (MOPA) transmitter based on a classic design from the early 1920s. It uses a UV-201 oscillator tube driving a VT-25 tube — a modern equivalent to a UV-202 — to generate “a few watts” on 486 kHz. His modulator consists of another VT-25, which uses a large inductor in the RF amplifier’s plate supply to serve as a Heising modulator. The audio program comes from a laptop computer.

“Heising modulation was used in World War I as an easy way to achieve AM in rigs such as those used in aircraft,” Justin said. “My particular Heising modulator can deliver only around 60% modulation, so an audio processor is used to help boost the average volume level ahead of the modulator tube.”

Justin uses far more modern technology to boost “the few watts” of modulated RF to drive a modified Hafler 9505 solid-state 500-W audio amplifier. “The idea for the amp came from W1TAG and W1VD,” he said, “and information on using such an amp on the 630 and 2200-meter ham bands can be found on the web.” After a multi-pole low-pass filter, the carrier output is 150 W.

Justin’s antenna is a Marconi T, crafted from a 160-meter dipole some 60 feet above ground and fed with open-wire line, which is shorted at the transmitter end. A homebrew variometer — constructed from 14-gauge wire wound on a piece of 4-inch diameter PVC pipe — is placed in series to resonate the antenna, which is fed against an extensive ground system. “Most of the RF is lost due to the ohmic losses of the ground system, but at least 15 W ERP is possible, depending on the dampness of the soil. Damp soil helps lower the ground losses,” Justin said.

Click here to read the full article on the ARRL News.

Listener reports may be sent to Brian Justin, WA1ZMS, at his QRZ.com address.

If you would like more information about Brian Justin and WI2XLQ, check out our interview with him in 2013. Indeed, I successfully heard the 2013 WG2XFG broadcast and posted this audio clip on the Shortwave Radio Audio Archive.

Additionally, SWLing Post reader, George Stein has a very personal connection with radio pioneer, Reginald Fessenden: click here to read his story.

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Ron’s thoughts on RFL200 and Q-Stick longwave antennas

Many thanks to SWLing Post contributor, Ron, who shares his thoughts on comparing two portable longwave antennas:

To begin, for reference, check out this post where The Professor reviews the RFA200. Also, check out the following video from the replies of that post:

Both the RFL-200 and the Q-Stick came in today.

Performance of both was very nearly identical but for now the Q-Stick wins on price ($67.50 vs. $75.78 delivered) and the Q-Stick does both LW and MW.

But Gerry says he’s going to close RadioPlus early next year so-presumably-
that will leave just the RFL-200 and its REA-200 sibling.

The “200” no doubt comes from the length, 200mm or 8 inches…the Q-stick
uses a 7-3/4 inch ferrite bar which is probably why the similar performance.

There is one thing: the small tuning knob is not hard to turn on the RFL-200
as it was on the REA-200 tested earlier but a bigger knob would be nice.

But the tuning cap uses a 1/8th inch shaft so finding a larger knob is too
much bother, most are for 1/4 inch shafts.

By comparison the Q-Stick has a nice big knob and is quite easy to tune.

So for now the Q-Stick would be the better buy, but don’t tarry.

[One more note,] if you want the most bang for your buck, forget both of these, get
a PK Loop
for $90.60 delivered (be sure to specify the 155-500 kHz model).

Thanks for sharing your thoughts, Ron!

Click here to check out the RFL200 longwave antenna on eBay.

(Click here to view the RFA200 mediumwave version.)

Click here to check out the Q-Stick antenna at Radio Plus. 


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Hamcrafters VLF Converter to be produced in Fall 2018

Many thanks to SWLing Post contributor, Ron, who notes that Hamcrafters appears to be planning a replacement for the Palomar VLF converter.

Here’s the product description:

The Hamcrafters VLF Converter is based on the original Palomar design and converts 10 KHz – 500 KHz to 4.010 to 4.5 MHz. This allows use of your HF Receiver or Transceiver and all its filters, noise blankers, DSP, and memories while tuning the VLF band. Modern HF radios have poor sensitivity in the VLF range (by design). Using this converter with a simple wire antenna will allow receiving of navigational beacons, time signals, and other VLF signals.

The Palomar is well-known among longwave DXers but hasn’t been in production for some time. Indeed, Ron adds, “The last two original Palomars went for $343 and $260 on eBay. Is there a demand? You bet!”

Thanks for the tip, Ron.

Click here to check out the Hamcrafters VLF Converter product page.

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Grimeton Radio / SAQ LF transmitter on the air May 1, 2018

Alexanderson alternator in the SAQ Grimeton VLF transmitter.

(Source: ARRL via Mike Hansgen)

Low-frequency World Heritage Grimeton Radio Station, SAQ, will transmit from Sweden on May 1 as participation in the European Route of Industrial Heritage’s “Work It Out” observance.

“As part of the event, we plan for the first SAQ transmission since 2016,” said Lars Kalland, SM6NM. The transmitter start-up will begin at 0930 UTC, with the transmission to follow on 17.2 kHz CW at 1000 UTC.

A live video stream of the event will be available. Kalland said no QSL cards will sent, nor will SAQ post a list of reports, but SAQ does invite brief listener reports via e-mail.

“We sincerely hope that all the SAQ transmission on 17.2 kHz will go as planned,” Kalland said. “But, as always, there is a reservation that the transmission [may be] cancelled on short notice.”

Click here to read on the ARRL website.

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