Category Archives: Longwave

Radio physics explained: The Luxemburg-Gorky effect

Get it while you still can: The Luxemburg-Gorky effect

by 13dka

The Radio Luxembourg longwave transmitter Junglinster in the 1930s [RTL Group]

“In radiophysics, the Luxemburg-Gorky effect (named after Radio Luxemburg and the city of Gorky (Nizhny Novgorod)) is a phenomenon of cross modulation between two radio waves, one of which is strong, passing through the same part of a medium, especially a conductive region of atmosphere or a plasma.” (Wikipedia)

That sounds pretty abstract, right? In my own words, imagine your radio is tuned to a station on let’s say 162 kHz, 500 miles away. Somewhere in the middle between your receiver and the 162 kHz transmitter is a station transmitting on a different frequency, let’s say 234 kHz. The Luxemburg effect is that you can hear the modulation of the 234 kHz transmitter in the middle, on the 162kHz station you are receiving. The effect is not depending that much on the frequency/wavelength though, the longwave station could affect medium wave stations and it has been created using shortwave frequencies far apart.

It was observed first in 1932, when listeners of the Swiss Beromünster 60kW medium wave station built just one year prior also heard a bit of Radio Luxemburg’s longwave transmitter (250kHz) on the Beromünster frequency (653kHz until 1934). Of course this was assumed to be some kind of crosstalk within the receivers and probably drove radio engineers insane until 1933, when Bernhard D.H. Tellegen, a Dutch electrical engineer and inventor suggested the true origin of the effect: The new (1932) 150kW Radio Luxemburg longwave transmitter in Junglinster was directly modifying the ionosphere hundreds of kilometers above, it “heated” the ionosphere in a way that it made the plasma’s charge and reflectivity follow the amplitude modulation of Radio Luxemburg, thus modulating waves of other wavelengths crossing this part of the ionosphere.

Practical demonstration

Even if you’re living in Europe, you may never have witnessed that effect and according to this article by Paul Litwinovich, chances to observe this in the US are rather slim, due to the relatively low power of the stations. I’m in Europe but never noticed it either – until recently: Continue reading →

13dka Reviews: The new 2022 “Belka” (generation 3) general coverage receiver

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The new 2022 “Belka” (generation 3) general coverage receiver

by 13dka

Since its introduction in 2019, the super-tiny Belka (back then called “Belka DSP”) shortwave receiver sure gained an enthusiastic followership among SWLs and hams. The main reason for this is certainly the way how the Belka is incredibly small yet playing in a different league than the various consumer grade, Chinese mass-production radios, particularly the DSP-based ultraportables: The Belka is an all-mode shortwave communications receiver with a completely different (direct conversion SDR) architecture, developed and produced by a radio enthusiast (Alex, EU1ME) in a small mom&pop shop in Belarus.

In case you’ve never heard about it amidst all the buzz about more popular brands, here’s the skinny:

The Belka offers true allmode (including NFM and CW) reception with a proper 400 Hz CW filter and individual settings for the low and high filter slopes for AM, FM and SSB. It has an AM sync detector and comes with a 0.5ppm TCXO-controlled local oscillator for absolutely spot-on, calibration-free frequency precision and stability, which makes SSB or ECSS reception of broadcast stations a pure joy. The second iteration “Belka DX” brought a slightly extended coverage down to 1.5 MHz and an I/Q output for panadapter display and/or processing via your favorite SDR software.

All Belkas are quiet and very sensitive radios with a surprisingly robust front end, the filters are better and its AGC works like you’d expect it from a communications receiver, without the artifacts and distortion the DSP radios are infamous for, and of course smooth, non-“muting” tuning in variable steps down to 10Hz.

The Belkas have no built-in speaker (available as option tho) but really excellent audio on headphones and external speakers and they actually give my Icom IC-705 a run for its money in terms of reception quality, and they do that for up to 24 hours on a single charge of the internal Li-Ion battery. This stunning feature set is crowned by the best performance on a telescopic whip antenna ever – the Belkas have a high-impedance (>10 kOhm) antenna input optimized for this whip and taking it on a walk is (really!) like having a big rig with a big antenna in tow…

Despite all this goodness setting the Belka(s) quite fundamentally apart from most (if not all) current and former, even much higher priced portables and simultaneously putting it solidly into pricey tabletop territory, it hasn’t put Tecsun et al out of business for a couple of reasons: One reason is that it can only be obtained from Alex in Belarus, which is now often assumed to be impossible (it isn’t, more on that later). Another reason is that it doesn’t try to compete with aforementioned multiband radios from China, so there is no FM broadcast band and – until now – no AM BC band, but most owners and potential buyers particularly in the US really wished it had at least the latter. Well, Alex obviously heard us! After the Belka DSP and the Belka DX, the new Belka is just called “Belka”, so in order to avoid any ambiguity I’m going to refer to this model as “Belka 2022”.

What’s new?

The most prominent addition to the Belka 2022 is the extended 0.1-31 MHz coverage, the previous version only started receiving at 1.5 MHz. With LW and MW included, its “pseudosynchronous” detector (as featured in venerable radios from Harris, Racal or Drake), the great filtering and the great frequency precision for hassle-free ECSS reception are promising that the “squirrel” is now an ultra-ultraportable companion for MW DXers as well.

Continue reading →

Belka DX updated to now cover mediumwave and longwave

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Many thanks to SWLing Post contributor, Dave Garr, who writes:

I have some interesting news for all of those Belka DX fans, Alex the guy behind this magnificent receiver has just announced the introduction of a new model. Ok so it is still called the Belka DX but it has now got a total frequency coverage of 100KHz to 31MHz so those that have put off buying because of lack of Long wave and Medium wave have now had their prayers answered. There has been no fanfare announcement about this but they have just updated their website with the new added frequency range. I am just waiting for the first review to appear before committing my hard earned cash.
Regards
Dave Gurr

Click here to check it out.

Excellent news. I’m sure this will make the Belka DX even more popular than it already is. I have to assume a ferrite bar hasn’t been added (there isn’t much room for one in the Belka series) so you would need to pair a proper MW/LM antenna antenna in order to fully take advantage of the new bands.

Thank you for the tip, Dave!

Matt’s 2022 Portable Loop Antenna Shootout

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

Matt’s 2022 Portable Loop Antenna Shootout

by Matt Blaze, WB2SRI

Followers of this blog may be familiar with my “shortwave radio shootouts” that I post from time to time. The idea is to compare how well different radios demodulate the exact same signal. Basically, I take a bunch of radios, hook them up to the same antenna via an RF distribution amplifier, tune the radios to some distant signal, and record the audio output from them simultaneously. Sometimes that kind of comparison can be more revealing of actual real-world performance than lab measurements or technical specifications.

The other day, I decided to do the same thing, but for antennas instead of radios. Essentially, I inverted the setup. Instead of hooking up different radios to the same antenna, I hooked up identical radios to different portable antennas and recorded them demodulating the same signals at the same time.

In this first of perhaps a series of these antenna shootouts, I wanted to compare three portable amplified magnetic loop antennas. When I say “portable” here, I mean broadband antennas that can pack reasonable compactly for travel and that can be set up and broken down easily for use “on location”, say on a picnic table or hotel balcony, or perhaps installed temporarily on a roof, without too much fuss.

The antennas are:

– The Wellbrook FLX1530LN with a 1 meter diameter loop of LMR400 coax. This is my “standard” portable antenna (I use a telescoping broom handle for the support; I wrote about it here as the “signal sweeper” last year). Excellent performance, but on the bulky side for travel. Performs well from LW through HF. Not cheap, at about USD 225 including shipping for the amplifier and power injector, but not including the loop, mounting hardware, or feedline.

– The Wellbrook FLX1530LN with a 0.5 meter diameter loop of RG142 (a stiff “aircraft grade” version of RG58 that holds it shape well at this size). I used some 1/2 inch PVC pipe as the vertical support. Because of the smaller diameter loop and thinner coax, it packs down to a much smaller and lighter package than the 1 meter LMR400 version.

– The K-180WLA, an inexpensive (about USD 60) 0.5 meter loop from China, sold on eBay and Amazon. The loop is steel wire (which can be wound down to a small diameter for transport), and the kit includes everything you need, including a rechargeable power injector. (However, the power injector uses a noisy voltage booster, so I substituted my own bias-T injector for these experiments). Ostensibly covers LW through VHF, but the low end coverage is, shall we say, somewhat aspirational, as you will see.

– I also recorded, for comparison, the built-in ferrite bar (for LW/MW) and whip antenna (for HF) of the receiver.

This is, of course, only a small sampling of portable loop antennas, both commercial and homebrew. But I wanted to start with what I had on hand and with what meets my own needs. (I omitted from consideration loops that require tuning, since I want to be able to install the antenna without needing access to it every time I change frequency).

For each signal captured, I oriented and positioned each antennas to maximize signal quality, taking care to move them away from each other and interfering metal objects. So you’re hearing (approximately) the best each antenna had to offer (on my roof under suboptimal band conditions).

The receivers I used were four Sangean ATS-909×2 portable LW/MW/SW/FM/Air radios. I believe this to be the best currently available (relatively inexpensive) portable shortwave receiver on the market. It has excellent performance (and is admirably resistant to overload and intermod when used with an active antenna). It lacks a sync mode, but that’s rarely implemented well on portable radios anyway. As a practical matter, it has a good line-level output jack, and I already happened to own four of them.

As in my other shootouts, for each signal, there are a total of five recordings: a monoaural recording of the audio from each of the four antennas, plus a narrated stereo recording comparing a reference (the 1M Wellbrook) on the Left channel with each of the other antennas in succession on the Right channel. The stereo recording is intended as a quick overview, but it will only make sense if you listen in stereo, preferably with good headphones. (You can switch the earcups to get a quick comparison as you listen.)

Continue reading →

BBC World Service: Licence fee spending to be cut £30m

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Many thanks to SWLing Post contributor, Jonathan Marks, who notes that BBC Director General Tim Davie announced a digital strategy along with a number cuts following the BBC licence fee settlement. This was all outlined in his “A digital-first BBC“ speech to staff this afternoon.

I’ve pasted the full copy of his speech below, but regarding the BBC World Service, here is an excerpt:

“The Government’s commitment to extend its £94m annual funding for the World Service for a further three years is very welcome. But UK licence fee funding for the World Service, which has been around £254m in recent years, is now running at over £290m including World News – a level that is unsustainable following the licence fee settlement.

We will set out plans in the coming weeks for how we will initially reduce licence fee spending on the World Service by around £30m by the start of 2023/24, while protecting the full breadth of languages.

At the same time, our strategic review will identify the right longer-term model for a digital-first World Service and lay out a strong case for more investment from government over the coming years. This case for a strengthened World Service is compelling but we can only expect UK licence fee payers to fund so much.”

In addition, they hope to save £500m annually by cutting services such as Radio 4 Extra, Radio 4’s Long Wave service, and Radio 5 Live’s mediumwave transmitter network.

The Director General’s speech to staff, of course, primarily focused on being a world-class digital and on-demand provider.

Here’s the full text of the speech via the BBC Media Centre:

A digital-first BBC

BBC Director-General Tim Davie’s speech to staff on 26 May 2022

Published: 26 May 2022

Good afternoon everybody.

Today, in our centenary year, I want to set out a vision of how we keep the BBC relevant and offer value to all audiences in an on-demand age.

I will cover three things: the pressing need to build a digital-first BBC; how we spend our money now that we have the certainty of public funding for six years; and how we keep reforming the way we work. Continue reading →

Video: Frans compares the GRAHN GS5 SE – VLF2 with a large loop antenna

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Many thanks to SWLing Post contributor, Frans Goddijn, who shares the following note and video originally posted on his blog:

Mr Grahn of https://www.grahn-spezialantennen.de/ had to stop working for a couple of months (medical reasons) but now he is back and I was able to get one of his highly sensitive Very Low Frequency modules to fit on my Grahn GS5-SE antenna tuner.

As before, the delicate device (“treat like glassware, do not throw”) was extremely well packed for its safe and intact arrival.

Click here to view on YouTube.

Click here to view Frans’ post which includes additional photos.

HanRongDa HRD-747: Expanding reception to include longwave

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Many thanks to SWLing Post contributor, Dan Robinson, who shares the following video which shows how connecting an external antenna to the HDR-747 extends reception range down to longwave: