Category Archives: Software Defined Radio

CommRadio CR-1: a superb travel radio

The CommRadio CR-1 in Taos, New Mexico

If you’re a regular reader, you’ll know that I’ve been on the road for the past three weeks, and have enjoyed some quality radio time in New Mexico and Colorado. While I brought four portables along (the CommRadio CR-1, the Sony ICF-SW7600GR, the Tecsun PL-380, and the Tecsun R1212A), when conditions were favorable and I wanted to chase a little DX, I chose the CommRadio CR-1.

I’ve sung the praises of the CR-1 as a great travel radio in the past, when it accompanied me on several shorter trips, but this particular road trip afforded me some quality time with this little rig.

What makes the CR-1 such a great radio for travel?

Excellent sensitivity and selectivity
Wide frequency coverage (150 kHz – 30.000 MHz, 64.0 – 260.0 MHz, 437.0 – 512.0 MHz)
Internal battery powers the CR-1 for hours at a time (meets FAA regulations, too; you can pack it and fly with confidence)
Charge or power the radio from a generic phone USB charger or 12 V power supply (indeed, the CR-1 can be powered from a variety of sources–anything from 6-18 Volts)
Mil Spec tested and tough
Compact footprint; this one is as small as most shortwave portables
Lightweight
OLED display that works from a variety of viewing angles
Resin feet can even be removed if packing space is severely limited
Very quick to deploy

The CR-1, hooked up to my Zoom H2N digital recorder, on the balcony of our Keystone, Colorado condo

One con of the CR-1 is that its front panel function buttons are not backlit. Fortunately, there are only six buttons, so it was easy to commit them to memory: I did so much outdoor nighttime listening, I can now operate the CR-1 in the dark.

Although the CR-1 is basically a tabletop SDR, it reminds me very much of the Palstar R30C I once owned and Lowe receivers I’ve used in the past–simple and effective.

The photo at the top of the post was taken in the back garden of a friends’ home in Taos, NM. Though you can’t see this in the photo, it was hooked up to a Par Electronics EF-SWL wire antenna at the time. It took five or so minutes to hang the EF-SWL in a tree, but took me only a few seconds to pull the CR-1 from a small flight case, plug in the antenna, and have it on the air. I charged the CR-1 prior to the trip so I didn’t even need a power supply. In fact, the internal battery powers the CR-1 long enough, I only charged it perhaps twice on the whole trip.

A flight case I purchased for $3 at a charity store holds the CR-1, the Sony ICF-SW7600GR and the Tecsun PL-380. The case is pretty much bullet proof and protects its contents even if dropped or heavy items placed on top.

A flight case I purchased for $3 at a charity store holds the CR-1, the Sony ICF-SW7600GR and the Tecsun PL-380. This case is fairly bullet-proof, protecting the contents even if dropped or heavy items are placed on it.

The CommRadio CR-1a

CommRadio recently introduced the CR-1a, identical to the CR-1 in every respect but with the addition of a USB I/Q output, making it a very capable SDR when connected to a PC–and simplifying the update process to one step (the CR-1 requires two steps).

In conclusion? My appreciation for this rig has grown. If you’re searching for a capable travel receiver, certainly consider adding the CommRadio CR-1 or the CR-1a to your list of considerations.

London Shortwave refines his tablet-based portable SDR

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One of the great things about the SWLing Post is that readers share their varied–and highly creative–methods of playing radio. A few weeks ago, SWLing Post reader, London Shortwave, shared his portable SDR set-up with us; he uses this outdoors to mitigate London’s heavy radio interference. Dennis Walter, president of Germany-based Bonito, commented, and later posted an alternative portable SDR solution using the Bonito RadioJet IF receiver.

Below, London Shortwave shares a guest post (also viewable on his blog) which describes in detail his design for his portable SDR around the FunCube Dongle Pro+ and an 8″ Windows tablet, and explains how effectively it works for him. This post includes recordings and a video; it’s an excellent tutorial:

DESIGNING A PORTABLE SDR SYSTEM

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:

listen to ‘Channel Africa received in London, UK’ on Audioboo

listen to ‘Radio Nacional da Amazônia received in London, UK’ on Audioboo

listen to ‘Zanzibar Broadcasting Company received in London, UK’ on Audioboo

listen to ‘Radio Australia received in London, UK’ on Audioboo

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

Portable SDR on Toshiba Encore 8″ Tablet from London Shortwave on Vimeo.

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!

Best application for the SDR-IQ on a MacBook Air?

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I’m plotting travels soon and plan to take my RF Space SDR-IQ along for the ride.

I’ve noted a number of excellent open source applications that work with the SDR-IQ, but many of them don’t work on the Mac OS X operating system. Those that do work on Mac OS X seem to lack the ability to make spectrum and audio (AF) recordings.

I had considered installing Windows 7 on my MacBook Air (as a dual boot) and running an app like SDR#, but I simply don’t have the storage space to effectively house two operating systems on the Air’s solid state drive.

I’m curious if anyone has an SDR application recommendation. Please comment if you do!

Designing a truly portable SDR

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SWLing Post reader, London Shortwave, is working on a portable SDR (software defined radio) system based on his Toshiba Encore 8″ Windows tablet, FunCube Dongle Pro+, and supported by the excellent SDR# application. Today, he shared this photo of his entire kit, including his comments. If you’re interested in a similar portable SDR, take note of the USB isolator and extra (AA battery) power supply.

London Shortwave plans to make an enclosure for the SDR, AA power supply, and USB isolator.

And although it may be easier said than done, it would be super if this enclosure has the same footprint as the Toshiba tablet, and the whip antenna can be mounted on the enclosure…He would then essentially have a case that he could attach to the tablet for instant portable shortwave radio fun. (Oops–did I just raise the bar for you? Ha!)

Thanks for sharing, London Shortwave!

Recording the 2014 World Cup Final

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Sunday was the FIFA World Cup Final, and not only was I looking forward to the game, but (to tell the truth) I was also looking forward to recording the game via the BBC World Service for the Shortwave Radio Audio Archive. Due to the BBC WS cuts, part of me fears this may be a last chance to capture this radio and sports history.

If you would like to hear the recordings of the World Cup Final, skip to the bottom of this post. But if you want to know how I managed to make the recordings, and why I made the choices I did, feel free to continue reading…Warning: full-on radio geek tech ahead!

Making the recording

I had two SDRs (software defined radios) at my disposal: the Elad FDM-S2 and my trusty WinRadio Excalibur. To record this match, I choose to use an SDR rather than a tabletop receiver for several reasons, namely:

I wanted to make a spectrum recording so that I could record more than one frequency at a time;
SDRs make recording radio content on the fly much easier than using a tabletop receiver, which must be connected to an external audio recorder, and I wanted ease of use so I could enjoy the game, too.

Propagation was rather mediocre Sunday, and there were only three feasible BBC World Service English frequencies I could tune in mid-afternoon, none of which, of course, were targeting North America:

11,810 kHz from Ascension Island
13,660 kHz from Woofferton, UK
15,400 kHz from Ascension Island
9,915 kHz from Woofferton, UK (starting at 20:00 UTC)

My hunch was that either 13,660 or 15,400 kHz would be my best bet for the early part of the match (pre-game starting at 18:30 UTC, half time at 20:00 UTC), however, I knew they would drop off after the first half of the game. And 11,800 kHz would be my best bet in the latter part of the game, unless 9,915 kHz happened to be stronger.

In the past, 11,800 had served me quite well for afternoon BBC listening, but yesterday there was an unscheduled religious broadcaster on 11,825 that was causing interference a full 30 kHz on either side of their carrier! During my pre-game check of the frequency, each attempt I made to block this broad interference was unsuccessful–very frustrating.

Which SDR?

The FDM-S2 is a fine SDR, and I was very tempted put it to the test. But while the Elad FDM-S2 is quite capable of making very wide spectrum recordings (up to 6 MHz) and could easily record all four frequencies on four different meter bands at the same time, I decided to use the WinRadio Excalibur, instead.

Why? If 11,800 kHz was my only viable frequency option in the latter half of the game, I needed a receiver that could sync to the less noisy lower sideband of 11,800 kHz. While Elad plans to add USB/LSB selectable synchronous detection in the next version of their SDR application, it currently does not have this capability.

I suppose, too, I feel more comfortable with the WinRadio Excalibur; I’ve been using it now for well over two years. If something were to go wrong during the broadcast, I knew I could diagnose it quickly on the Excalibur.

In addition, the Excalibur can do both a spectrum recording and up to three individual AF recordings at the same time (though limited within a 2MHz bandwidth). I’m not sure if Elad has plans for this in their next SDR.

Setting up the Excalibur

The Excalibur only has a 2 MHz bandwidth for spectrum recordings. I knew if I focused on the middle frequency of 13,660, I would be able to record it and either 15,400 or 11,810 at the same time, but not all three.

The first half of the match, I recorded both 13,660 kHz and 15,400 kHz in a 2 MHz wide spectrum recording. At the same time, I recorded the audio (an AF recording) from 13,660 kHz, which was consistently the stronger of the two frequencies.

Half time

By 20:00 UTC, I knew both 13,660 and 15,400 kHz would stop transmitting and I would need to either hop to 11,810 kHz or 9,915 kHz.

While maintaining a good audio recording of 13,660, I stopped the 2 MHz spectrum recording and moved it to encompass 13,660 and 11,810 kHz. A quick check proved that 11,810 was the strongest station. Fortunately, the interference above 11,810 had quieted somewhat at that point, and by using the LSB sync lock, this noise was successfully mitigated a bit.

Still, I could hear a chuffing sound coming from the splatter 11,825 was producing. So I enabled the notch filter and widened it to 2 kHz. By shifting it around in the upper side band, I was able to find the “sweet spot” where most of the splatter noise was canceled. I then started the audio recording on 11,810 a few minutes prior to 20:00 UTC, making a little audio overlap with simultaneous recording on 13,660.

Syncing on the lower sideband and using the notch filter in the upper sideband mitigated most of the interference.

Syncing on the lower sideband and using the notch filter in the upper sideband mitigated most of the splatter interference.

In the end, I was very pleased with the results of the recordings. While capturing the BBC World Service isn’t exactly like snagging rare DX, I felt I had a lot riding on this recording, so pre-game preparations were necessary, especially since the Excalibur couldn’t record spectrum from 9,915 to 15,400 kHz.

And in theory, had I used the Elad FDM-S2, I could have recorded the entire chunk for three hours and then revisited the material later to make audio recordings from the AF.

The recordings

For your listening pleasure: the full 2014 World Cup final via the BBC World Service. This broadcast is broken into 3 sections: pre-game and the first half, second half, and extra time. Enjoy!

Pre-game and first half (13,66o kHz):

Second half (11,810 kHz):

Extra time and game wrap-up (11,810 kHz):

SDR# on a Toshiba Encore tablet PC

SDR# now has AM synchronous detection

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SWLing Post reader, London Shortwave writes with a remarkable story about the free SDR application, SDR#(or, “SDR sharp”). He writes:

“Two days ago, I emailed Youssef (SDR# developer lead) to ask if he would consider adding synchronous AM detection to his software at some point.

To my great surprise he e-mailed me back the same day and told me that it wouldn’t take him long to write the necessary code. A few hours later he sent me a preview copy of the software with the feature included (all I had to do was to swap one .dll file in the version I had installed at the time). The following day, he integrated it into the latest release!

With the new sync detector the software is rapidly becoming my favourite SDR application.

Here’s a demo video I made for Youssef (and everyone else!) to show how I’ve been getting on with it:

This is amazing–what’s especially impressive is that a first iteration of AM sync should be so well implemented. I love the way you can use the IF shift to block out interference within a sideband, much like USB/LSB selectable sideband. There are paid and OEM SDR applications that can’t do this.

London Shortwave: you’ve convinced me to see if SDR# will drive any of my receivers. Many thanks!