My submission to SWLing.com Virtual Radio Challenge II

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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A few days ago The SWLing Post published a challenge to their readers: given a budget of $1200, to put together the best possible shortwave radio listening set-up that can function completely off the grid in the Himalayas.

My solution is to fuse my two previous submissions to The Post - my response to the shortwave listening challenge for the remote Atlantic island of Tristan Da Cunha and my portable SDR design - and to add solar power.

FunCube Dongle Pro+ and Toshiba Encore 8" running SDR# in a London park

To recap, the tablet-based SDR set-up costs $643. My experiments with FunCube Dongle Pro+ and SDR# software have convinced me that this combination makes for one of the best shortwave listening experiences in its price range. Here are a few reasons why:

- FunCube Dongle Pro+ is a sensitive SDR.

- SDR# has an excellent noise reduction algorithm that often turns laborious DXing into comfortable listening. It also has a robust synchronous detector, which, combined with its passband tuning and noise reduction algorithms can unbury almost any station from the surrounding co-channel interference.

However, given the remoteness of the location and the fact that there is no reliable electricity grid to speak of, we need a few extras:

Solar Power

You may recall that in my portable SDR solution there are two sets of batteries that need to be recharged:

- Toshiba's built in Lithium Ion battery (via its USB port)

- 4xAA batteries for the Gomadic 5V Power Pack (used for supplying extra power to the SDR)

First, let's get a compact, foldable solar panel:

1. Powerfilm F16-1200 20W foldable solar panel

I would go with Powerfilm F16-1200 20W foldable solar panel  (buy it here for $210.99). Disclaimer: although I've never used any of the PowerFilm products or accessories, I have read good reviews of them from other radio enthusiasts. When folded, this solar panel measures merely 27.9cm x 16.5 cm - slightly smaller than an A4 notepad. Once fully opened, however, it can deliver 20W of power (15.4V, 1.2A), enough to charge the Toshiba tablet and 4xAA rechargeable batteries simultaneously.

To charge the AA cells, I would go with the Powerfilm RA-3b - 12V Battery Charger Pack for AA and AAA (buy here for $54.41) and the Powerfilm RA-2 12V Female Power Port Adapter (already included with F16-1200).

2. RA-3b - 12V Battery Charger Pack for AA and AAA

3. RA-2 12V Female Power Port Adapter

Although we only need 4 AA batteries for the Gomadic USB Power Pack, it's always nice to have some spare ones, just in case. I would throw in a pack of 12 Panasonic Eneloop AA 2100 Cycle Ni-MH Pre-Charged Rechargeable Batteries for $26.95.

4. 12 Panasonic Eneloop Rechargeable Batteries

The spares can be used in the following ways:

- To power the backup portable shortwave radio

- To have another batch ready when the batteries insde the Gomadic USB Power Pack run out.

- Using Gomadic, to charge the tablet outside daylight hours, for more daytime listening.

Now onto charging the tablet itself. For this I would use the Powertraveller Spidermonkey 4-Port USB Charger Hub at $38.76. Again, I haven't used this product, but according to the specifications it can charge up to 4 USB devices and accepts input power between 5V and 30V. The reviews are largely positive, so it seems like a safe choice.

5. Powertraveller Spidermonkey 4-Port USB Charger Hub

To connect the Spidermonkey hub to the solar panel we'll need the Powerfilm RA-16 - 3ft. Extension Adapter with 4.75mm Barrel cable (available here for $9.98)

6. RA-16 - 3ft. Extension Adapter with 4.75mm Barrel

If we want to charge both the tablet and the AA batteries simultaneously, the  Powerfilm PP-7 - Multiple Device Charger Cable accessory will come in handy (here for $24.99)

7. PP-7 - Multiple Device Charger Cable

Antenna Extras

Living off the grid has the advantage of there being minimal man-made radio interference. For this reason we can use a larger antenna than in my original proposal. I suggest buying 40m of POLYS18 Copper-Clad Steel Antenna Wire from Universal Radio (the total comes to $31.44), cutting it halfway, and attaching each half to one of the two antenna terminals on the Wellbrook HF Balun, mentioned in my previous article, thus creating a dipole.

Of course, this makes for a rather powerful shortwave receiving antenna that can easily overload the radio. We can solve this problem by connecting the balun's feedline output to the antenna terminal on the Global AT-2000 Antenna Tuner, $85 via 25 feet of GadKo BNC Male Copper Stranded Center Conductor Cable , $16.90. We should then connect the radio terminal to the short feedline cable of the FunCube Dongle Pro+ SDR, with the ferrite chokes left in place. We will need 2 x BNC female to PL259 Adapters, $6.49, to connect the BNC cables to Global's PL259 female sockets.

8. Global AT-2000 Antenna Tuner

9. 2 x BNC female to PL259 Adapters

10. GadKo BNC Male Copper Stranded Center Conductor Cable

Finally, here's a simple schematic diagram of how the antenna parts should be wired together:

Connecting all the antenna bits together

Backup Radio

The challenge article mentions that a back-up radio would be desirable in the event of other equipment failing. I suggest Tecsun PL-310 ET, available for $48.79 from Amazon. It's a very similar radio to the excellent Tecsun PL-380 (they use the same Silicon Labs chipset), but it has one notable advantage: an external antenna input! It takes a 3.5mm jack plug, so we'll need a BNC Socket to Composite 3.5mm Male Jack Plug Adapter, $2.01.

11. Tecsun PL-310 ET

12. BNC Socket to Composite 3.5mm Male Jack Plug Adapter 

The subtotal for all of the above comes to $556.71. Adding on $643 for the tablet-based SDR solution brings the total to $1199.71, just 29 cents below the budget limit!

Designing a portable SDR system

Update (15/11/16): this article describes my initial portable SDR configuration, which is now substantially improved. Jump to this post to see my current set-up.

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This article is a follow up to the submission I made to the SWLing Post a little while ago. In short, the idea was to combine the FunCube Dongle Pro+ USB-based software defined radio (SDR) with an 8" Windows tablet running SDR# to have a portable, on-the-go SDR solution.

The original inspiration

Tablet radio interference

At the outset, I thought that all that was necessary was a tablet (I chose Toshiba Encore 8"), the FunCube dongle itself and just some antenna wire. This turned out to be a naive assumption because the tablet's USB interface injected enormous amounts of radio frequency interference (RFI) into the SDR, making listening on some shortwave frequencies essentially impossible. Just to be sure that I wasn't being plagued by a defect of my chosen tablet model, I tried out the same set-up on a Dell Venue 8, with identical results.

To deal with the issue of tablet-generated RFI, I bought a galvanic USB isolator, which, in essence, is a box that breaks the electrical connection between the USB dongle and the tablet's USB interface while allowing USB data to pass through in both directions.

Heros Technology galvanic USB isolator

Additional power for the SDR

Connections

The isolator resolved the RFI issue completely, but created another problem altogether: the device specifications state that the isolator's power output is restricted to 100mA at 5V. This is sufficient for USB devices that are self-powered but not for the FunCube dongle that draws all of its power from the USB port to which it is connected.

USB Y cable

One way to supply extra power to a USB device is to use a "Y-cable". Such cables have one extra USB plug that can be attached to a source of additional power (for example, a USB power bank). This solution is commonly used to connect power-hungry items, such as large hard disks, to low-power, portable computing devices (laptops and tablets). Having bought this cable, my next step was to find/improvise a battery that meets the USB power specifications (5V, 500mA).

Yet more interference

My first thought was to use the mobile USB power bank that I use to charge my iPhone while on the go. After all, it already has a USB port and supplies power with the right voltage. Once again, my expectations were confounded and RFI reared its ugly head! The power bank radiates significant interference into the circuit because it uses a switching regulator to maintain steady voltage. Luckily, I came across Gomadic's portable AA battery pack with regulated 5V output that emits way less interference than any of the other USB batteries I tried (my intermediate solution used 4 rechargeable AA batteries and a makeshift USB connector, and although this resulted in zero additional interference I decided that it's not safe to supply the SDR with unregulated voltage that doesn't match the rest of the circuit). I used the handy passthrough USB voltmeter I bought in Maplin to check that Gomadic's nice-looking gadget does indeed give out 5V as advertised.

So, what can one do with the remaining RFI from the additional power supply? It turns out that it can be mitigated quite effectively by inserting a balun (item 10 on Figure 2) between the SDR and the antenna wire (item 12). The balun is connected to the SDR with a coaxial cable (the "feed line", item 11). Additionally, ferrite choke rings (item 9) attached to the feed line help reduce this RFI further: winding the feed line through the choke rings several times is sufficient. However, neither the balun nor the chokes are effective enough to replace the USB isolator! It appears they only help with the noise generated by the power supply, which is relatively minor anyway.

Cost vs Portability

When SWLing Post published the details of my intermediate solution, Dennis Walter - one of the engineers behind Bonito RadioJet - popped up in the comments section and suggested that my setup is too tedious, as it involves lots of cables, and that his SDR is superior in terms of portability and the supplied software. While I haven't had the chance to evaluate RadioJet, I pointed out that the cost of his radio is significantly higher than that of all of my components put together. I also mentioned that the free SDR# software I use is superb: it sounds excellent and offers a number of features that many software packages and conventional radios don't have. So, having finalised my design, I thought that it might be time to tally up the cost and listen to the results.

Below is the full component list:

1) Toshiba Encore 8" tablet $194

2) On The Go USB host cable for Toshiba's micro USB connector: $7

3) Heros Technology USB Isolator: $125

4) USB Y cable with two males + 1 female plugs: $8 

5) Gomadic Portable AA Battery Pack with regulated 5V output: $20 

6) Gomadic female USB connector tip: $6

7) FunCube Dongle Pro+: $208

8) USB volt-meter (optional): $33

9) 2 ferrite choke rings: $10

10) Wellbrook HF Balun: $50

11) Feedline cables $7

12) 6 metres of thick copper antenna wire: $8

Adding up the prices of items 2 - 12 (and excluding the optional voltmeter) brings the total cost to  $449 vs. Bonito RadioJet's $689. For the price difference you can throw in the Toshiba tablet at $194 and still have some change, enough to buy a carrier bag and perhaps even a nice pair of headphones!

Figure 1. Radio components

Figure 2. Antenna components

In terms of portability, the entire setup fits nicely into an 11" laptop carrier bag.

Figure 3. Packing the components into an 11" carrier bag

Figure 4. Ready to go

Setting things up in the field is not particularly cumbersome, either:

Figure 5. Portable SDR setup in action in a local park

As for the results, listen to the below snippets and be the judge. The only thing I will say is that none of my other portable radios have ever given me this kind of performance, not even with the long wire antenna attached:

And while we're at it, here's a demo video:

At one point I wanted to build an enclosure to house the FunCube dongle, the power supply and the USB isolator in a single tidy unit, but I no longer see the need. It's easy to pack all of those items into the carrier bag and also they are all useful individually: the USB isolator can be paired with other SDRs, and I recently discovered a neat additional use for the Gomadic battery pack.

Well, that brings me to the end of this post. I hope my design will inspire you to come up with your own portable SDR system, and that you will share your results with me in the comments section. Happy listening!

Portable operation of Newstar DR111 DRM receiver

NewStar DR111 is one of the few commercially available consumer DRM radios. In my experience, the radio works quite well with an external antenna (such as the Wellbrook ALA1530 magnetic loop).  However, one of the main drawbacks of this unit is that it doesn't work off batteries, making portable operation cumbersome. The built-in whip antenna is long and has demonstrated fair performance in the past, but indoor reception with it is typically hindered by local radio frequency interference (RFI).

Radio enthusiasts have engineered some ingenious workarounds for this problem. For example, Alokesh Gupta used a DC-AC inverter to power the receiver's wall-wart 5V DC adapter from a 12V car battery, while Tudor Vedeanu improvised a portable AA battery pack that connects to the radio via a DC plug. Both methods are awesome hacks, but the former is quite power-hungry, while the latter only allows rechargeable batteries to be used (four alkaline AA batteries will supply well over 5 volts and this creates the risk of radio damage).

Although I bought my DR111 almost one year ago, it hasn't been getting much use; in the table-top / external antenna setting, software defined radio applications allow for excellent DRM reception. However, yesterday I discovered one undocumented feature of the unit that makes portable operation really easy: it turns out that DR111 can draw power via its USB port!

NewStar DR111 DRM receiver connected to Gomadic AA battery pack via the USB port

Enter the Gomadic Portable AA Battery Pack with regulated 5V output and its USB connector accessory. No risk of power overload and no need to solder wires and plugs together. Below is a video of DR111 running on four AA alkaline batteries in a local park earlier this morning:

While in DRM mode, I enjoyed listening to Radio Exterior de España and Radio France International (the latter being especially impressive as its signal is rather weak and the time of day didn't allow for good propagation on the corresponding frequency). I also tuned into the final hour of Radio Habana Cuba's morning analogue shortwave broadcast.

One important thing to note is that while there are other portable USB power solutions out there, some of them inject quite a bit of RFI into the receiver because of their switching voltage regulator design. Fortunately, in the case of Gomadic, this artefact isn't too strong and doesn't get in the way of decent radio reception. I look forward to listening to All India Radio's afternoon DRM broadcast on 15140 kHz later today and perhaps I might even catch Radio New Zealand International's DRM signal like this shortwave listener did!

Cuban radio

Courtesy of emiana

To me, Cuba has always been shrouded in mystery and yet is full of romanticism. Its music and culture combined with its history of being a semi-closed state both during the Cold War and more recently have made it into one of the more exotic locations to try to catch on the airwaves.

Some interesting facts about the country in this regard:

• It was one of the first countries to have radio and television in the Americas.
• There was media censorship in place before the Cuban Revolution, under the dictatorship of Fulgencio Batista.
• During the early years of the revolution there remained a number of media outlets that opposed Fidel Castro's new regime, until the Cuban Broadcasting Institute was firmly established.
• There are three radios for every ten Cuban citizens.
• Computer ownership was outlawed until 2007 and Internet access is still amongst the most expensive in the world, adjusted for the median monthly wage.

Radio Habana Cuba

Courtesy of Universidad de La Habana

Cuba has one international radio broadcaster, Radio Habana Cuba (RHC), and several clandestine stations broadcasting at it (more on those in a moment). There is plenty of information about RHC on its Wikipedia page (and even more in this paper about the history of the station) although one thing that stood out for me is the fact that during the Cold War it relayed (propaganda) news items from Vietnam, North Korea and the USSR after receiving teletype bulletins from those countries (retweeting, the old school way).

These days, RHC broadcasts towards several regions:  the USA (in English and Spanish), Europe (in French, Portuguese and Arabic), Central America (in English, Spanish, French and Creole), South America (in French, Spanish and even in Quechua - the language of the native populations of Bolivia and Peru) and Africa (in English). For a small country, such broadcasting schedule is ambitious and shows an impressive regional and international reach. Oddly, there seems to be no dedicated broadcast directed at Europe in English or Spanish and the easiest way to catch either in London is to tune in to their beam directed at New York on 6060 kHz from about 0220 UTC (after The Voice of Islamic Republic of Iran stops interfering with the signal on the same frequency). At 0500 UTC the programming switches from Spanish into English.

The short path between La Habana, Cuba and London, UK. It is easy to see why the New York beam might offer some hope of reception in London.

Radio Habana Cuba is nothing short of amazing if you are into Latin music and listening to this station is also a very good way to learn Spanish as the presenters speak slowly and clearly. As a bonus, shortly after the 0400 UTC newscast you can invariably hear a fragment from one of Fidel's public speeches, taken from the Cuban national archives. Here is my recording of that entire hour:

There are some other programming gems, such as El Mundo de la Filatelia (the world of stamp collecting), the likes of which one would be hard-pressed to find elsewhere, as well as regular extensive features on the Cuban healthcare and education systems.

A celebratory Radio Habana Cuba stamp, courtesy of dvaldemoro

The station does have Internet streams for both its international and Spanish broadcasts. However, they are frequently offline and their audio quality is often actually worse than the shortwave transmissions, especially if you are located in an interference-free area (sadly, not in my case) and have a good antenna. You can get the latest list of Radio Habana Cuba's frequencies here.

Clandestine Stations

Courtesy: The Monitoring Magazine, November 1985

In its ideological battle against Cuba, the United States have employed a number of shortwave radio stations broadcasting towards the Caribbean island. One of the more famous was Radio Swan, which was set up by the CIA to promote an uprising against the Castro regime and used during the abortive Bay of Pigs invasion to assist with the landings of the US troops by transmitting coded messages. These days, the most prominent US government-funded clandestine station targeting Cuba is the Miami-based Radio Martí, which is primarily staffed by Cuban immigrants. From listening to it with my limited comprehension of Spanish I understood that they use correspondents in Cuba who have American mobile phones that can make calls outside the country (which were obviously smuggled in). Some programs are very propaganda-driven, brutally exposing the deficiencies of the current Cuban economic system, while a few others, such as Avanza Cuba (Cuba Forward) are more positive in their tone and explore Cuba's potential. Below is my short recording of one of the station's evening broadcasts:

The above snippet contains a segment on Pope Francis's birthday dinner with the homeless and a brief description of the US immigration system.

Cuban Numbers Stations

Courtesy: Dirk Rijmenants

A numbers station is a shortwave station that transmits a sequence of encrypted messages, usually in the form numbers read out by an automated voice. During the Cold War, such stations were very active on both sides of the Iron Curtain and it is hypothesised that they were used to send ciphered instructions to spies. Cuba operates a network of these stations, and they have previously been implicated in Cuban anti-US espionage cases. In 2001, Los Cinco (the Cuban Five) were tried and convicted of spying for Cuba in the United States. It is alleged that the group had received and decoded messages that had been broadcast from Cuban numbers stations.

By complete chance, I stumbled across one such station that is actually very interesting. The numbers, spoken in Spanish, are followed up by shrieking modem-like tones (for those who remember the dial-up days of the Internet).

It turns out that this transmission was in the so-called Hybrid Mode and the shrieking tones are in fact computer files being sent in Redundant File Digital Transfer mode called DIGTRX. This mode allows the recipient to connect their shortwave receiver's headphone jack to the mic input their PC's sound card and decode the files as they are being sent across the airwaves. The inventor of this mode came across the station - nicknamed HM01 - by accident, and decoded the files with his own software but couldn't read them: as one might expect, they were encrypted. Below is my recording of HM01, which I caught straight after RHC finished its Spanish broadcast:

It might come across as amusing to find spies employing this somewhat dated way of obtaining information in our digital age. It does, however, offer one huge advantage: the recipient leaves no trace of ever having received the message!

The Cuban Five

The Cuban Five, mentioned above, are a group of Cuban intelligence officers who resided in the United States and were convicted of espionage by a US court. The Cuban media have regular features on their continued detention in the United States and there are major events staged throughout the year that are dedicated to calls for their release. One such event was The Concert for The Five that took place on September 12, 2013 in La Habana. Radio Rebelde, Cuba's arguably most popular national radio station founded by none other than Che Guevara, was airing it live and Radio Habana Cuba joined in by rebroadcasting Rebelde's coverage internationally. I was fortunate to catch a part of this broadcast and record it:

It goes without saying that I will keep tuning in to Cuban radio. In fact, the whole concept of using this older way of listening somehow feels distinctly Cuban.

Channel Africa: Nelson Mandela Memorial Service Broadcast

Earlier today, the official memorial service for Nelson Mandela was held at Soweto's FNB stadium in South Africa's capital, Johannesburg. I managed to catch and record Channel Africa's shortwave broadcast on 15235 kHz at 17:00 UTC that reported on the occasion and detailed some of the late leader's biography. Channel Africa is South Africa's official international radio station that transmits out of Meyerton.

Click here to download the recording.