Simulating shortwave audio artefacts

Sunday, October 25, 2015

Readers of my blog may remember that some of my recent posts have been dedicated to mitigating urban radio interference on shortwave, or, in other words, making the signal sound as clear and intelligible as possible in harsh reception conditions. But what if you wanted to go the other way? That is, take a clean audio recording (perhaps an MP3 of a song) and make it sound like it has travelled many thousands of miles over shortwave and picked up a few characteristic audio artefacts along the way, such as interference from adjacent stations, fading and heterodynes. It turns out that this can be done rather easily by downloading REAPER (Rapid Environment for Audio Production, Engineering, and Recording - a digital audio workstation created by Cockos) and importing AM_Radio_Sim project created by a REAPER forum member, Ollie. The project author writes:
These projects attempt to simulate AM radio in most of its characteristic effects by "macro-modeling" the actual signal chain from transmitter over ionosphere to receiver and speaker, recreating the interdepency of on-channel and off-channel signals in the receiver. 
This goes way beyond simple filter and distortion type of AM simulation, it recreates most of distance-related detrimental effects of AM radio like characteristic intermodulation and distortion effects created by off-channel signals, multipath propagation/selective fading and in the (cheap) receiver frontend. 
Typical offchannel signals/interference are created in realtime. In addition to that special noise, you can simply add audio files on the "splatter" tracks in order to create a realistic frequency neighborhood, they will rock your virtual IF filter slopes almost like the real thing. 
The bottom line is, when you need an AM sound that won't get debunked as "bandpass with distortion" [...] this is supposed to do it.

Here is my demo of his REAPER project (AM_Radio_Sim_41m) in action. The first 1:20 of the video is the original audio and the rest is the shortwave simulation. You will notice that just after I switch on REAPER I move the transmission and fading levels up and down to experiment with creating a sense of deep signal fading.

I'm sure I'll be using this trick to add long-distance romanticism to some of my home-made music mixes!

Update: below is a somewhat more realistic simulation of shortwave audio artefacts. It's a "recording" of an imaginary station that I came up with and called "The Voice of North Sudan". Here I keep moving the transmission and fading levels up and down constantly to create a more realistic audio fading pattern.


Shortwave playlist part 4

Monday, October 19, 2015
There's just too much good music on shortwave! Below is the fourth volume of the shortwave playlist for your listening pleasure.

1. Gürol Ağırbaş - Four Seasons - Spring
Radio Algerienne Chaine 3, June 2015

Gürol Ağırbaş is a musician from Turkey, born in Istanbul. (Wikipedia)

2. Ehab Tawfik - Ya Abu El Oloub
Medi 1, April 2014

Ehab Tawfiq (Arabic: إيهاب توفيق‎) (born in Cairo on January 7, 1966) is an Egyptian singer. He is seen one of the top singers in the Arab world, and is especially revered in his hometown. In 1995, he received his master's degree for his thesis: "The Egyptian Song in the Second Half of the Twentieth Century". Not satisfied with just a masters, Ehab worked toward his Doctorate in Music and Arabic singing, completed in April 2002. The doctorate was entitled "The Methods of Performing Arabic Singing in Egypt during the second half of the last century". (Wikipedia)

3. Joe Jackson - Caravan (5 minutes into the video clip)
Radio Rebelde, April 2015

David Ian "Joe" Jackson (born 11 August 1954) is a musician and singer-songwriter. Born in England, he lived in New York before moving to Berlin. His career, during which he recorded nineteen studio albums and garnered five Grammy Award nominations, spans from 1979 to today. (Wikipedia)

“Caravan” features the vocals of the Iranian singer Sussan Deyhim, performing the Farsi translation of  the song's lyrics.

4. Elis Regina - Alô! Alô! Marciano
Radio Nacional da Amazônia, May 2015

Elis Regina, born in Porto Alegre on March 17, 1945, was a Brazilian singer of popular and Jazz music. Before her untimely death at the age of thirty-six, she was widely regarded as Brazil's greatest living popular vocalist. (Wikipedia)

5. 5 Dong Ke - Doc Huyen Cam

Voice of Vietnam, October 2015

5 Dong Ke is widely regarded as the top girl group of Vietnam. From inception to date, the group has won several major music awards. (Wikipedia, translated from Vietnamese using Google Translate)


Submission to the Shortwave Archive Part 4: Radio Habana Cuba and Radio Rebelde

Saturday, October 17, 2015
More recordings from Cuba this week. My favourite of the two has to be the Radio Rebelde recording, as it contains the nightly Nosotros programme, brimming with Cuban music. These recordings don't sound particularly crisp — a combination of rather poor propagation conditions (making Rebelde's signal too jumpy even for my trusty Tecsun PL-660 and knocking its sync detector sideways a few times, until I switched to normal AM mode) and the wrongly adjusted input volume on my recorder in the case of RHC. However, it infuses the recordings with a certain vintage flavour, which seems appropriate. I will post some of my better quality recordings of Rebelde in the future; as for the clips below, the content certainly compensates for the less than ideal reception conditions!

Radio Rebelde: March 6, 2015

Radio Rebelde recorded in London, UK on March 6, 2015 at 0600 UTC on the frequency of 5025 kHz using a Tecsun PL-660 radio with a 4m long wire antenna, positioned outdoors. The transmitter is located in Quivicán, Cuba and has a power rating of 100 kW. This signal was received under poor propagation conditions, resulting in strong fading (QSB).

Click here to download the recording // Link to the original SRAA submission

Radio Habana Cuba (English): June 12, 2015

Radio Habana Cuba (English service) recorded in London, UK on June 12, 2015 at 0300 UTC on the frequency of 6000 kHz using a Tecsun PL-680 radio with a Lowe PR-150 preselector, two Wellbrook ALA1530S+ antennas (positioned indoors) and a DX Engineering NCC-1 phaser. The transmitter is located in Quivicán, Cuba and has a power rating of 250 kW. The recording has mild distortion because of an incorrect audio gain setting on the recorder.

Click here to download the recording // Link to the original SRAA submission


Radio hacking: reliable Radio Australia reception indoors

Thursday, October 15, 2015
Since my last post on dealing with urban radio interference on shortwave I have made additional progress with low-noise indoor reception. Although I have been fortunate to receive quite a few stations with my current set-up, Radio Australia had remained a difficult catch. The high levels of static present on its daytime frequency resulted in a poor overall listening experience. I am pleased to report that I have largely solved this problem by positioning my Wellbrook loop antenna horizontally. Below is a short demo video:

It appears that the source of local interference on 12065 kHz is directly below me and positioning the loop horizontally nulls this noise source. This is another demonstration of Wellbrook ALA1530S+ exceptional directional reception capability.


Shortwave playlist part 3

Tuesday, October 13, 2015
This shortwave playlist instalment is a little bit different. Some of the tracks are not the ones that I heard on the radio but are those I later found (and liked) after looking up the artist.

1. Simba Wanyika - Baba Asiya
Zanzibar Broadcasting Company, September 2015 — original song heard: Shilingi

Simba Wanyika was a Kenyan based band created in 1971 by Tanzanian brothers Wilson Kinyonga and George Kinyonga, and disbanded in 1994. Simba Wanyika and its two offshoots, Les Wanyika and Super Wanyika Stars, became some of the most popular bands in Kenya. Their guitar-driven sound, inspired by the Soukous guitarist Dr. Nico, combined highly melodic rumba with lyrics sung in Swahili. Simba wa nyika means "Lions of the Savannah" in Swahili.

[Rumba, also known as Soukous] is a popular genre of dance music that originated in the Congo basin during the 1940s, strongly influenced by Cuban son. The style gained popularity throughout Africa during the 1960s and '70s. (Wikipedia)

2. Alick Macheso - Tafadzwa
Radio Dialogue, May 2014

Macheso was born in 1968 in Shamva, 90 kilometres to the north of Harare, to parents of Malawian origin - a fact that was to inspire him to be able to speak and sing in five languages - Shona, Chichewa, Sena, Venda and Lingala.

He is well known throughout Sourthern Africa as one of the most successful singers and ranked among the best bass guitarist on the continent. He is Zimbabwe's best-ever selling artiste with his album Simbaradzo being the highest ever sold album in Zimbabwe, a record which is yet to be broken by any artiste in Zimbabwe to date. In recent years Macheso has risen to become an advertising face for many corporations with his recent achievement being an an ambassador for the Red Cross. (Wikipedia)

3. Cheb Khaled - La Camel
Medi 1, June 2014 — original song heard: Yamina

Khaled Hadj Ibrahim (Arabic: خالد حاج إبراهيم‎, born 29 February 1960), better known as Khaled, is an Algerian raï singer-songwriter and multi-instrumentalist born in Sidi El Houari in Oran Province of Algeria. He began recording in his early teens under the name Cheb Khaled (الشاب خالد, Arabic for "Young Man" Khaled, as opposed to the traditionalist Sheikh elders) and has become the most internationally famous Algerian singer in the Arab world and across many continents. His popularity has earned him the unofficial title "King of Raï". (Wikipedia)

4. Rivany - Telaga Dewa
Voice of Indonesia, October 2015

Kroncong (pronounced "kronchong") is the name of a ukulele-like instrument and an Indonesian musical style that typically makes use of the kroncong, the band or combo or ensemble (called a keronchong orchestra) consists of a flute, a violin, a melody guitar, a cello in pizzicato style, string bass in pizzicato style, and a female or male singer. (Wikipedia)

5. Te Vaka - Samulai
Radio New Zealand International, December 2013

Te Vaka is an Oceanic music group that performs original contemporary Pacific music or "South Pacific Fusion". The group was founded in 1995 by singer and songwriter Opetaia Foa'i in New Zealand. They have toured the world constantly since 1997 and have won a number of awards including "Best Pacific Music Album" award for their albums Tutuki (2004) and Olatia (2007) from the New Zealand Music Awards and "Best Pacific Group" in the 2008 Pacific Music Awards They have also been acclaimed by the BBC as "the world's most successful band playing original contemporary Pacific music." (Wikipedia)


Submission to the Shortwave Archive Part 3: Polskie Radio Jedynka and Antena Satelor

Saturday, October 10, 2015
This week's theme is Long Wave DXing. Long wave signals usually do not travel very far, even at night, so I am quite pleased with both of these catches, particularly with Antena Satelor, whose transmitter is five times less powerful than Jedynka's whilst being almost twice as far.

Polskie Radio Jedynka: December 25, 2013

Polskie Radio Jedynka recorded in London, UK on December 25, 2013 at 0004 UTC on the frequency of 225 kHz using a Lowe HF-150 radio with a Lowe PR-150 preselector and a Wellbrook ALA1530S+ antenna (positioned indoors). The transmitter is located in Solec Kujawski, Poland and has a power rating of 1000 kW. This is a local service targeted at the domestic audience. The recording is of the Polish Christmas service that was broadcast nationally.

Click here to download the recording // Link to the original SRAA submission

Antena Satelor: September 14, 2015

Antena Satelor, Romania recorded in London, UK on September 14, 2015 at 0100 UTC on the frequency of 153 kHz using a Lowe HF-150 radio with a Lowe PR-150 preselector and a Wellbrook ALA1530S+ antenna (positioned indoors). The transmitter is located in Brașov, Romania and has a power rating of 200 kW. This is a local service targeted at the domestic audience. The recording ends with the Romanian national anthem.

Click here to download the recording // Link to the original SRAA submission


Cool new feature on TwenteSDR

Wednesday, October 07, 2015
TwenteSDR is a web-controlled shortwave receiver located at the University of Twente in the Netherlands. Unlike many other remotely controlled receivers, it can be tuned by multiple users simultaneously by leveraging Software Defined Radio (SDR) technology. It is a popular online destination for shortwave radio enthusiasts when they are away from their listening posts. For readers unfamiliar with the service, below is a short demo showing TwenteSDR tuned into Radio New Zealand International on January 19, 2014.

Yesterday they added a new feature where it is possible to see what the entire shortwave spectrum looked like in the last 24 hours. I had a quick look and noticed an interesting pattern: it seems that there is almost a perfect inverse linear correlation between band openings (measured in kHz) and the time of the day.

24 hour view of the shortwave spectrum between 49 meters and 16 meters, taken from TwenteSDR on 07/10/2015. Download the full cached copy.

I wonder how propagation conditions (rather dismal in the last few days!) and the time of the year affect this relationship. I'll keep checking this plot on TwenteSDR to try to understand this better.

Propagation on 07/10/2015
Daylight map on 07/10/2015 courtesy of


Dealing with urban radio interference on shortwave

Monday, October 05, 2015
Shortwave radio listening is an exciting hobby, but for many of us city dwellers who either got back into it recently or tried it out for the first time not long ago, the first experience was a disappointing one: we could barely hear anything! Station signals, even the supposedly stronger ones, were buried in many different types of static and humming sounds. Why does this happen? The levels of urban radio frequency interference, or RFI, have increased dramatically in the last two decades and the proliferation of poorly engineered electronic gadgets is largely to blame. Plasma televisions, WiFi routers, badly designed switching power adapters and Ethernet Over Powerlines (also known as powerline network technology, or PLT) all severely pollute the shortwave part of the radio spectrum.

Does this mean we should give up trying to enjoy this fascinating medium and revert to using the TuneIn app on our smartphones? Certainly not! There are many angles from which we can attack this problem, and I shall outline a few of them below.

Get a good radio

The old adage "you get what you pay for" certainly holds true even when it comes to such "vintage" technologies as shortwave radio. Believe it or not, a poorly designed receiver can itself be the biggest source of noise on the bands. That is because many modern radios use embedded microprocessors and microcontrollers, which, if poorly installed, can generate interference. If the receiver comes with a badly designed power supply, that too can generate a lot of noise.

So how does one go about choosing a good radio? and have fantastic radio review sections, which will help you choose a robust receiver that has withstood the test of time. My personal favourites in the portable category are Tecsun PL310-ET and Tecsun PL680. If you want a desktop radio, investigate the type of power supply it needs and find out whether you can get one that generates a minimal amount of noise.

It is also worth noting that indoor shortwave reception is usually best near windows with at least a partial view of the sky.

Tecsun PL310-ET and Tecsun PL680, my two favourite portable shortwave radios.

Identify and switch off noisy appliances

Many indoor electrical appliances generate significant RFI on the shortwave bands. Examples include:

  • Plasma televisions
  • Laptop, and other switching-type power supplies
  • Mobile phone chargers
  • Dimmer switches
  • Washing machines / dishwashers
  • Amplified television antennas
  • Halogen lighting
  • LED lighting
  • Badly constructed electrical heaters
  • Mains extension leads with LED lights

Identify as many of these as you can and switch them all off. Then turn them back on one by one and monitor the noise situation with your shortwave radio. You will most likely find at least a few offending devices within your home.

Install an outdoor antenna

If you have searched your home for everything you can possibly turn off to make reception less noisy but aren't satisfied with the results, you might want to look into installing and outdoor antenna. That will be particularly effective if you live in a detached or a semi-detached property and have a garden of some sort. Of course, you will need a radio that has an external antenna input, but as for the antenna itself, a simple copper wire of several metres will do. An important trick is making sure that the noise from inside your home doesn't travel along your antenna, thus negating the advantage of having the latter installed outside. There are many ways of achieving this, but I will suggest a configuration that has worked well for me in the past.

Fig.1 Schematic for an outdoor dipole antenna.

I have used a three-terminal balun (positioned outdoors), and connected two 6 metre copper wires to its antenna terminals to create a dipole. I then connected the balun to the radio indoors through the feed line terminal using a 50Ω coaxial cable. In the most general terms, the current that is generated in the antenna wires by the radio waves flows from one end of the dipole into the other, and a portion of this current flows down the feed line into your radio. The balun I have used (Wellbrook UMB130) is engineered in a way that prevents the radio noise current from inside your house flowing into the receiving part of the antenna.

Wellbrook UMB130 balun with the feed line terminal disconnected

Antenna preselectors

There is a catch with using an outdoor antenna described above — the signals coming into your radio will be a lot stronger than what would be picked up by the radio's built-in "whip" antenna. This can overload the receiver and you will then hear many signals from different parts of the shortwave spectrum "mixing in" with the station you are trying to listen to. An antenna preselector solves this problem by allowing signals from a small yet adjustable part of the spectrum to reach your radio, while blocking the others. You can think of it as an additional tuner that helps your radio reject unwanted frequencies.

Fig.2 Schematic of a preselector inserted between the outdoor antenna and the receiver
There are many antenna preselectors available on the market but I can particularly recommend Global AT-2000. Although no longer manufactured, many used units can be found on eBay.

Global AT-2000 antenna coupler and preselector

Risk of lightning

Any outdoor antenna presents the risk of a lightning strike reaching inside your home with devastating and potentially lethal consequences. Always disconnect the antenna from the receiver and leave the feed line cable outside when not listening to the radio or when there is a chance of a thunderstorm in your area.

Get a magnetic loop antenna

A broadband loop antenna (image courtesy of

The outdoor long wire antenna worked well for me when I stayed at a suburban property with access to the garden, but when I moved into an apartment well above the ground floor and without a balcony, I realised that I needed a different solution. Having googled around I found several amateur radio websites talking about the indoor use of magnetic loop receive-only active antennas (in this case, "active" means that the antenna requires an input voltage to work). The claim was that such antennas respond "primarily to the magnetic field and reject locally radiated electric field noise"[*] resulting in lower noise reception than other compact antenna designs suitable for indoor use.

Interlude: signal to noise ratio

In radio reception, the important thing is not the signal strength by itself but the signal to noise ratio, or SNR. A larger antenna (such as a longer copper wire) will pick up more of the desired signal but, if close to RFI sources, will also pick up disproportionately more of the local noise. This will reduce the SNR and make the overall signal reading poorer, which is why it is not advisable to use large antennas indoors.

The other advantage of a loop antenna is that it is directional. By rotating the loop about its vertical axis one can maximise the reception strength of one particular signal over the others, once the antenna is aligned with the direction from which the signal is coming (this is termed "peaking" the signal). Similarly, it is possible to reduce the strength of a particular local noise source, since the loop is minimally sensitive to a given signal once it is perpendicular the latter's direction (also known as "nulling" the signal).

It is further possible to lower the effect of local noise sources by moving the antenna around. Because of the antenna's design, the effect of radio signals is mostly confined to the loop itself as opposed to its feed line. Most local noise sources have irregular radiation patterns indoors, meaning that it is possible find a spot inside your property where their effects are minimised.

Many compact shortwave loop antennas require an additional tuning unit to be attached to the loop base (much like the preselector described above) but broadband loops do not. Wellbrook ALA1530S+ is one such antenna that is only 1m in diameter, and it was the one I chose for my current apartment. I was rather impressed with its performance, although I found that I need to use a preselector with it as the loop occasionally overloads some of my receivers when used on its own. Below is a demo video comparing using my Tecsun PL680's built-in antenna to using the radio with the Wellbrook loop.

As you can hear, there is a significant improvement in the signal's readability when the loop is used.

Experiment with a phaser

Although the loop antenna dramatically reduces the levels of ambient RFI getting into the radio,  I also have one particular local noise source which is way too strong for the loop's nulling capability. Ethernet Over Powerlines (PLT) transmits data across domestic electrical circuits using wall socket adapters, as an alternative to wireless networking. It uses the same frequencies as shortwave, which turns the circuits into powerful transmitting antennas, causing massive interference. One of my neighbours has PLT adapters installed at his property, which intermittently become active and transmit data. When this happens,  it is not merely noise that is generated, but a very intense data signal that spreads across the entire shortwave spectrum, obliterating everything but the strongest stations underneath. Fortunately, a mature piece of radio technology called antenna phasing is available to deal with this problem.

Fig.3 The principle of antenna phaser operation (adapted from an original illustration in Timewave ANC-4's manual)

Signal cancellation using phase difference

A phaser unit has two separate antenna inputs and provides one output to be connected to the radio's external antenna input. The theory of phase-based signal cancellation goes roughly as follows:

  • The same radio signal will arrive at two different, locally separated antennas at essentially the same time.
  • The phase of the signal received at the first antenna will be different to the phase of the same signal received at the second antenna.
  • This phase difference depends on the direction from which the signal is coming, relative to the two antennas.
  • The phaser unit can shift the phases of all signals received at one antenna by the same variable amount.
  • To get rid of a particular (noise) signal using the phaser unit:
    • the signal's phase at the first antenna has to be shifted by 180° relative to the signal's phase at the second antenna (thus producing a "mirror image" of the signal received at the second antenna)
    • its amplitude at the first antenna has to be adjusted so that it is the same as the signal's amplitude at the second antenna
    • the currents from the two antennas are then combined by the unit, and the signal and its mirror image cancel each other out at the unit's output, while the other signals are preserved.

Noise sampling antenna considerations

To prevent the possibility of the desired signal being cancelled out together with the noise signal — which can happen if they both come from the same direction relative to the antennas — one can use the set-up illustrated in Figure 3, where one antenna is dedicated to picking up the specific noise signal, while the other is geared towards receiving the desired broadcast. That way, even if the phases of both the noise and the desired signals are offset by the same amount, their relative amplitude differences will not be the same, and thus removing the noise signal will not completely cancel out the desired signal (though it will reduce the latter's strength to some extent).

It is possible to use any antenna combination for phase-based noise signal cancellation. However, one has to be careful that, in the pursuit of removing a specific noise source, one does not introduce more ambient RFI into the radio system by using a poorly designed noise-sampling antenna. After all, the phaser can only cancel out one signal at a time and will pass through everything else picked up by both antennas. This is particularly relevant in urban settings.

For this reason, I chose my noise sampling antenna to also be a Wellbrook ALA1530S+. The additional advantages of this set-up are:

  • It is possible to move both loops around to minimise the amount of ambient RFI.
  • By utilising the loops' directionality property, one can rotate the noise sampling loop to maximise the strength of the noise signal relative to the desired signal picked up by the main antenna loop.

Two Wellbrook ALA1530S+ antennas combined through a phaser

And now onto the phaser units themselves.

Phaser units

DX Engineering NCC-1 (image courtesy of

I have experimented at length with two phaser units: the MFJ 1026 (manual) and DX Engineering NCC-1 (manual). Both solve the problem of the PLT noise very well, but the NCC-1 offers amplitude and phase tuning controls that are much more precise, making it a lot easier to identify the right parameter settings. Unfortunately this comes at a price, as the NCC-1 is a lot more expensive than the MFJ unit. As before, a preselector is needed between the phaser and the radio to prevent overloading.

Below is a demo of DX Engineering NCC-1 at work on my neighbour's PLT noise. I have chosen to use my SDR's waterfall display to illustrate the nefarious effect of this type of radio interference and to show how well the NCC-1 copes with the challenge.

Cost considerations

Fig.4 Final urban noise mitigation schematic

It would be fair to say that my final urban noise mitigation set-up, shown in Figure 4, is quite expensive: the total cost of two Wellbrook antennas ($288.38 each), a DX Engineering phaser ($599.95) and a Global AT2000 preselector ($80) comes to $1257. That seems like an astronomical price to pay for enjoying shortwave radio in the inner city! However, at this point another old saying comes to mind, "your radio is only as good as your antenna". There are many high-end shortwave receivers that cost at least this much (e.g. AOR AR7030), but on their own they won't be of any use in such a noisy environment. Meanwhile, technological progress has brought about many much cheaper radios that rival the older benchmark rigs in terms of performance, with Software Defined Radios (SDRs) being a particularly good example. It seems fair, then, to invest these cost savings into what makes shortwave listening possible. You may also find that your RFI situation is not as dire as mine and you only need some of the above equipment to solve your noise problems.

Filter audio with DSP

If you have implemented the above noise reduction steps but would still like a less noisy listening experience, consider using a Digital Signal Processing (DSP) solution. There are a number of different approaches and products available on the market, and I shall be reviewing some of them in my next post. Meanwhile, below are two demo videos of using DSP while listening to shortwave. The first clip shows the BHI Compact In-Line Noise Elimination Module at work together with a vintage shortwave receiver (Lowe HF-150). The second video compares using a Tecsun PL-660 portable radio indoors on its own and using the entire RFI mitigation set-up shown in Figure 4 together with a DSP noise reduction feature available in the SDR# software package, while using it with a FunCube Dongle Pro+ SDR. As a side note, it is worth remembering that while DSP approaches can make your listening experience more pleasant, they can't recover what has been lost due to interfering signals or inadequate antenna design.

Set up a wireless audio relay from your radio shack

The above RFI mitigation techniques can result in a rather clunky set-up that is not particularly portable, confining the listener to a specific location within their home. One way to get around this is by creating a wireless audio relay from your radio shack to the other parts of your house. I did this by combining the Nikkai AV sender/receiver pair and the TaoTronics BA01 portable Bluetooth transmitter:

Head for the outdoors!

So you have tried all of the above and none of it helps? As a last resort (for some, but personally I prefer it!), you can go outside to your nearest park with your portable radio. After all, if shortwave listening is causing you more frustration than joy it's hardly worth it. On the other hand, you might be surprised by what you'll be able to hear with a good receiver in a noise-free zone.

Received on 14/03/2014 15:59 GMT in London, UK with Tecsun PL-660 + 6m wire antenna, outdoors (synchronous AM detector, lower side band, narrow bandwidth)


Many of the above tricks and techniques were taught to me by my Twitter contacts. I am particularly grateful to @marcabbiss@SWLingDotCom, @K7al_L3afta and @sdrsharp for their advice and assistance over the years.


Submission to the Shortwave Archive Part 2: Radio Damascus and Radio Habana Cuba

Saturday, October 03, 2015
This week's theme is "countries in the news". With the decision by Russia to start its pro-Assad military air campaign in Syria and Pope Francis's recent visit to Cuba, I chose the following two recordings:

Radio Damascus, Syria: October 23, 2013

Radio Damascus, Syria recorded in Moscow, Russia on October 23, 2013 at 2242 UTC on the frequency of 783 kHz using a Tecsun PL380 portable radio. The transmitter is located in Tartus, Syria and has a power rating of 600 kW. This is a local service targeted at the domestic audience. There were several short poor propagation spells throughout the recording, after which the signal would recover.

Click here to download the recording // Link to the original SRAA submission

Radio Habana Cuba: September 13, 2013

Radio Habana Cuba recorded in London, UK on September 13, 2013 at 0232 UTC on the frequency of 6060 kHz using a Tecsun PL380 portable radio with a 4 meter clip-on long wire antenna extension. The transmitter is located in Bauta, Cuba and has a power rating of 100 kW. This broadcast was a relay of Radio Rebelde's live coverage of the Cuban Artists' "Concert for the Five" that took place at Havana Jose Marti Anti-Imperialist Plaza. "The Five" referred to the four Cuban nationals remaining in US custody of the five originally imprisoned in the US in the early 2000s. They were released on December 18, 2014 in exchange for the freeing of Alan Gross by the Cuban authorities, as part of a deal that marked the beginning of the restoration of the US-Cuban relations.

Click here to download the recording // Link to the original SRAA submission


Radio hacking with TaoTronics Bluetooth transmitter

Friday, October 02, 2015

Indoor shortwave listening outside the shack

I was inspired by the following 1930s illustration from the book On the Short Waves, 1923-1945, which describes how a seasoned DXer would have listened to shortwave around the house

I achieved a similar result by combining the Nikkai AV sender/receiver pair and the TaoTronics BA01 portable Bluetooth transmitter:

Monitoring while recording from radios with no line out

Tecsun PL-660 doesn't have a line out, which means that when recording from it one has to use a pair of headphones to listen to it simultaneously. Most portable speakers I've tried generate tremendous amounts of RFI when connected directly to the receiver. I solved this problem by using TaoTronics transmitter and a Bluetooth enabled portable speaker, together with a cable that splits the audio output into two, so the transmitter and the audio recorder can both be connected to the radio. The recording is of Radio Australia and was made in London, UK on 09/04/2014 at 15:43 BST.

Perhaps one day we will see a decent portable shortwave radio with a built-in Bluetooth audio transmitter?


Shortwave playlist part 2

Tuesday, September 29, 2015
Below is the second instalment of the shortwave playlist series for your enjoyment.

1. Salif Keita - C'est Bon C'est Bon
VOA Africa, August 2015

2. Marinella - Zografismena Sto Charti
Voice of Greece, September 2015

3. Grupo Casuarina - Rosa Morena
Radio Nacional da Amazônia, August 2014

4. Beny More - Mata Siguaraya
Radio Habana Cuba, December 2013

5. Daoudi - Lamina Aamri Mabkit
Medi 1, September 2014


Submission to the Shortwave Archive Part 1: Furusato No Kaze and KCBS Pyongyang

Saturday, September 26, 2015
This post marks the start of my weekly submissions to the Shortwave Radio Audio Archive. This week's theme is North Korea.

Furusato No Kaze: September 17, 2015

Furusato No Kaze recorded in London, UK on September 17, 2015 at 1600 UTC, on the frequency of 9960 kHz using SDRPlay with SDR# software and a 2 x 6m long wire dipole. The transmitter has a power rating of 100 kW and is located in Palau. From NorthKoreaTech:

Shortwave radio remains a vitally important way to reach into North Korea because of the total lack of international communications offered to its citizens.
Furusato no Kaze (ふるさとの風, Hometown Wind) is run by the Japanese government and targets any Japanese citizens that were abducted by North Korea and remain alive in the country. There are two programs: Furusato no Kaze in Japanese and Nippon no Kaze (il bon ue baram, Japan Wind) in Korean. The first and last broadcasts of each day come from transmitters in Taiwan while the rest are from Palau.

You can also hear what appear to be North Korean jamming attempts in the background.

Click here to download the recording // Link to the original SRAA submission

KCBS Pyongyang: September 17, 2015

Korean Central Broadcasting Station, Pyongyang recorded in London, UK on September 17, 2015 at 1605 UTC, on the frequency of 9665 kHz using SDRPlay with SDR# software and a 2 x 6m long wire dipole. The non-directional transmitter has a power rating of 50 kW and is located in Kanggye, DPRK. From NorthKoreaTech:

The Korean Central Broadcasting Station (KCBS) (Korean: 조선중앙방송, Chinese: 朝鲜中央放送, Japanese: 朝鮮中央放送) is the main domestic radio network in the DPRK. It sits under the Central Broadcasting Committee of the DPRK (called the Radio and Television Committee of the DPRK until 2009). 
KCBS broadcasts from 5am to 3am local time via a network of mediumwave and shortwave transmitters that cover the nation. The powerful transmissions can easily be heard in neighboring countries, including South Korea where some of its frequencies are jammed. 
A central program is broadcast from Pyongyang on most transmitters through the entire broadcast day, but some are reported to carry regional programming between 2pm and 3pm. 
All programming is in Korean and includes music, talk and news.

The station appears to be a difficult catch in Europe because of the relatively low power and the non-directional mode of the transmission, and because of frequency clashes with China Radio International, Radio Cairo and Radio Voz Missionaria of Brazil. Indeed this recording was made in the small time window between CRI's Pashto and Hausa broadcasts, the latter of which can be heard starting at the end of the recording.

Click here to download the recording // Link to the original SRAA submission


Longwave DXing: Radio Romania Antena Satelor

Saturday, August 01, 2015
In the early hours of Friday morning, just before going to bed, I inserted a fresh pair of AA batteries into my analogue Roberts R9962 portable radio and fired it up for some late night listening. Despite its simple looks and the lack of bells and whistles, R9962 is a fine radio. However, I was immediately reminded that my home is plagued by severe interference on HF from the adjacent apartments and that using this radio on its own on shortwave is simply not feasible in such conditions. The only relatively quiet frequencies were in the lower part of the long wave spectrum. I switched the band selector into the LW position, put the radio on the window sill and started slowly tuning the dial. I heard our BBC Radio 4 on 198 kHz, a few French stations further down the frequency range but none of this seemed particularly interesting for some reason. Just as I reached the very bottom of the dial I heard a very faint signal against the backdrop of constant static crashes and crackles. I rotated the radio so that its ferrite bar antenna would be maximally aligned with the incoming signal, and although it was still a bit weak, I immediately recognised it — what I was hearing was none other than Radio Romania's Antena Satelor on 153 kHz! Long wave signals usually do not travel very far, even at night when the ionosphere allows for some long distance opportunities in this part of the spectrum, so at 2000km this was certainly some impressive DX. I have certainly had many nights when I couldn't hear it with my Wellbrook loop antennas and all the additional anti-interference gear in place.

After listening for a few minutes I realised that I'd better record this — who knows when the bands will open up like that again! At night, Antena Satelor play traditional Romanian music, and at the start of the recording I caught what I think was the end of the program featuring some of their songs from the 1930s. Then, at the top of the hour the station switched gears and started playing Romanian folk music instead, something that is now quite familiar to me after a few years of listening to Radio Romania International on shortwave. However, one more surprise was in store: the signal started becoming stronger steadily and after about ten minutes the little red light on the radio came on — now we were definitely tuned in! Nonetheless, even while the signal was very faint, I was impressed by how reliably the R9962 was pulling it out from the static, something that can be heard by comparing the volume of the audio with the strength of the static crashes. I hope there will be more nights when I can hear Antena Satelor with such clarity!

Below is the full recording for your enjoyment (153 kHz on 31/07/2015 at 0055 UTC):

Click here to download the recording instead


Shortwave playlist part 1

Thursday, April 30, 2015
Over the past two years, shortwave radio listening has exposed me to lots of new music from around the world. Starting from this entry, I shall occasionally post short playlists of some of the more interesting records I have heard.

1. Ibrahim Maalouf - Sensuality
Medi 1, July 2013

2. Morenito - Los Almonteños
Radio Exterior de España, June 2014

3. Harold Lopez Nussa Trio - Bailando Suiza
Radio Habana Cuba, December 2013

4. Alexis Boulgourtzis - Choris Prova
Voice of Greece, November 2013

5. Lin Hai - Happy Together
China Radio International, August 2013


Recording the spectrum with portable SDR

Friday, April 17, 2015
Update (15/11/16): this article describes an older version of my portable SDR configuration. Jump to this post to see my current set-up.

As my friend Thomas Witherspoon frequently points out in his excellent blog, one of the great things about using a software defined radio package like SDR# is that one can record entire regions of the frequency space instead of a single station. Although I've always wanted to try this out, my home is plagued by tremendous electromagnetic interference and the challenge has always been finding the optimal equipment settings for a single station. Under such circumstances, capturing parts of the spectrum didn't really make sense. Now that I finally have a convenient portable SDR solution, I decided to give spectrum recording a go.

On the evening of 15/04/2015 I went out to a nearby park and set up my equipment as follows:

I used a thin SMA to BNC wire to reduce the strain on FunCube's RF front end connector.
Hiding the gadgets from prying eyes inside the carrier bag (all listening done via a pair Bluetooth headphones)
The feed line cable has a velcro strap which is great for attaching the former to a tree branch.
12m of wire were wrapped around the tree branches (two 6m wires connected to the balun in a dipole fashion)

I fired up SDR#, set the centre frequency to 12095 kHz and started recording the spectrum to disk. This is what it looked like:

FunCube Dongle Pro+ spectrum circa 1600 UTC on 15/4/2015 (click above to enlarge)
The frequency window of the captured spectrum was 192 kHz, which is the maximum that the FunCube Dongle Pro+ can provide. While this is only a small fraction of the entire shortwave spectrum, it it is still possible to simultaneously capture a fairly large number of radio signals within it. When I got home I replayed the spectrum data through SDR# several times to extract the following station recordings:

Voice of America (Somali service), 12055 kHz, 1600 UTC. The strongest signal in the above screenshot (unsurprising, as it happens to be transmitted from the closest geographical location). The SDR# / FunCube Dongle Pro+ combo did well not to produce audio artefacts given that the carrier peak occasionally inched close to 0db.

Radio Australia, 12065 kHz, 1559 UTC. SDR#'s passband tuning and synchronous detection were of invaluable help here because of VOA's blowtorch beam was destroying the lower sideband of Radio Australia's signal. A cheap portable radio almost certainly wouldn't cope in these circumstances!

NHK Radio, 12045 kHz, 1559 UTC. SDR# did a brilliant job of pulling this exceptionally weak station out from the static. However, once the nearby VOA powerhouse got going on 12055 kHz at 1600 UTC, it buried this signal almost completely, which you can hear towards the end of this short recording.

Voice of Korea, 12015 kHz, 1602 UTC. North Korea's international radio service in German. SDR# allows the user to select arbitrary audio filter widths, which was useful for this signal as its bandwidth was roughly 20kHz, making the sound come out in somewhat higher fidelity.

Radio Free Asia, 12075 kHz, 1600 UTC. Broadcasting from Tinian Island in the Pacific Ocean, the station comes through remarkably well. That is, until the Chinese start jamming it, which can be heard in the later part of the recording.

BBC World Service, 12095 kHz, 1559 UTC. BBC's signal is surprisingly crisp considering it is coming all the way from Madagascar.

Radio Farda, 12005 kHz, 1559 UTC broadcasting from Udon Thani in Thailand.

Radio Dialog, 12115 kHz, 1602 UTC broadcasting from Talata-Volondry in Madagascar (presumably airing the recording of their earlier Sunday morning program).

IBRA Radio, 12125 kHz, 1600 UTC broadcasting from Yerevan in Armenia.

Trans World Radio, 12160 kHz, 1602 UTC broadcasting from Tashkent in Uzbekistan.

All in all, I am really pleased with what I could pick up. If you have SDR# installed you can be the judge by downloading the spectrum recording itself. Unzip the file, select it after choosing "IQ file" as the input source in the application, and press play (make sure you tick "Swap IQ" and "Correct IQ" in radio options).


Portable SDR update

Friday, April 03, 2015
Update (15/11/16): this article describes my old portable SDR configuration. Jump to this post to see my current set-up.

This is a quick entry describing an update to my portable SDR setup. Readers may remember that my previous configuration suffered from the tablet's radio interference leaking into the FunCube Dongle Pro+ SDR. I solved the problem by using a galvanic USB isolator and a separate portable USB power supply for the dongle. When I posted this configuration on in August, Alexander DL4NO advised me that it's possible to get rid of the USB isolator. Because my balun has two terminals, he said, I can use it to make a dipole antenna (an antenna with two wires) that balances the radio current before it gets passed down into the SDR dongle, which ought to prevent tablet interference from getting into the antenna system.

At the time I wasn't sure this would work. His other suggestion — using a ferrite ring choke on the antenna feedline cable — didn't do much to suppress the tablet noise, which made me assume that it was FunCube Dongle's design that was at fault, and that the noise was getting in from the USB end and not via the antenna.

Wellbrook UMB130 balun
However, when I finally tried out Alexander's suggestion, I could not believe what a drastic effect the addition of the second wire has: as soon as I connect it to the balun, the noise disappears, even with the USB isolator "out of the loop". This simplifies my portable SDR configuration substantially. Below is a demo video:

There is no sound here because I was listening to Radio Australia's 12065 kHz signal using a pair of Bluetooth headphones. Note the low noise floor and the absence of any interference on the spectrum. This has a substantial impact on the overall cost:

1) On The Go USB host cable for Toshiba's micro USB connector: $7
2) FunCube Dongle Pro+: $186
3) Wellbrook HF Balun: $60
4) Feedline cables $7
5) 12 metres of thick copper antenna wire: $16

The total without the tablet comes to $276, and if you buy an HP Stream 7, you only need to add $90 more. A complete on-the-go SDR solution for $366 doesn't sound too bad, does it? Many thanks to DL4NO for making my set-up that much more portable!