Radio hacking with TaoTronics Bluetooth transmitter

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

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

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

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

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

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.

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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.

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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!

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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.

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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.

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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.

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

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

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

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

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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

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

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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 SWLing.com 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!