Digital Radio Mondiale

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Have you run across an odd sounding digital transmission in one of the SWBC bands? Possibly, you heard a DRM transmission. Digital Radio Mondiale (DRM) is a digital audio broadcasting technology that claims to provide FM quality sound over shortwave radio. It uses MPEG-4 codecs.

Here is an example of a DRM signal. This one is Vatican Radio on 17815 kHz at 1610 UTC on May 5, 2012. First, the digital transmission as you would hear it tuned on a regular SW radio: DRM signal

Below is a waterfall showing the DRM signal, between two traditional AM transmissions:

Comparing the transmissions, you can see how easy it is to distinguish a DRM transmission from a regular AM transmission. The signal intensity is pretty much constant over the entire 10 kHz bandwidth, and there is no strong carrier in the center, with the symmetrical sidebands around it.

Below is a zoom into the entire DRM signal:

And here is what the resulting audio sounds like, after being processed by DRM software: DRM audio

For this reception, I used a netSDR receiver with a 635 ft sky loop antenna, running the SdrDx software. SdrDx was set to USB mode with a 10 kHz wide filter, since the DRM transmissions are 10 kHz wide. The output of SdrDx was fed through Soundflower (a virtual sound device) to Dream, which does the DRM decoding.

Below is the main Dream window, showing some basic information about the DRM signal, such as the name of the station, target area, etc. This is all obtained from the DRM signal itself. The audio bitrate is also displayed. There is only one audio channel on this transmission, there could be multiple channels.

The next window shows some detailed information about the DRM transmission, such as the signal to noise ratio, various decoding parameters and settings, a graph of the SNR, etc:

One thing to remember about DRM, it is like most digital transmissions – all or nothing. If the reception quality of the DRM signal is poor, the audio will completely cut out. So when reception is good, you get great audio. When it is poor, you get nothing.

Another point, about Dream itself. It is the poster child of open sores software. There’s no OS X binary on the download site. Download the source code, hunt around for zillions of libraries, compile and link the app (Wait! You’re not a programmer, you just want to use the app? Tough luck, kid). Lather, rinse repeat.

I did find a binary download link for Dream for Mac OS X here. It’s from 2009, but it seems to mostly work.

There is a DRM encoder called Spark. I am not aware of any pirates that have tried using DRM in their transmissions. They’d need a transmitter that can handle very wide (at least 10 kHz) audio in SSB mode. There are some lower quality DRM formats that use 4.5 and 5 kHz wide transmissions, with resulting lower quality audio. It might be an interesting experiment for some of the the more technically minded ops.

A good source for up to date DRM transmission schedules is the Shortwave Broadcast Schedules app, available for both the iPhone/iPad and Android. DRM transmissions are identified with the word DIGITAL in the station name.

Lies, Damned Lies, and Receiver Images

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   HF Weather Fax     
   For Android     

I have my SDR-14 receiver online, for some listeners to use. The other day, there was a logging of Trenton military aviation weather on 6950 kHz. I had not seen other reports of Trenton aviation weather on this frequency. And, since 6950 is a very popular frequency for pirate radio in the USA, this could cause some concern, as QRMing military stations is generally bad karma for pirates.

Here is a recording of Trenton Aviation as received on the SDR-14.

As it turns out, I had been running a recording of 6800-7000 kHz via another SDR, my netSDR. So I went back, and checked that recording at the same time the SDR-14 had picked up Trenton on 6950. Nothing. Nothing at all. And the netSDR is connected to a much better antenna than the SDR-14. Hmm. This is strange.

Last night, I was alerted that Trenton was again being heard on the SDR-14 on 6950 kHz. So I went and tuned in on the netSDR, and again heard nothing. I then decided to look for a schedule of frequencies used by Trenton, and found that they should be on 6754 kHz. I tuned in, and sure enough, there they were. Coming in very well, about S9+30 dB or so. Hmm… I did a quick calculation, and the difference between 6950 kHz and 6754 kHz is 196 kHz. 196 kHz, that sounds familiar. Why yes, that’s the I/Q sample rate of the SDR-14!

Now it all makes sense – the received signal on 6950 kHz is an image, a false signal generated by the receiver. It turns out that even SDRs are not immune to images. (Shhh… don’t anyone tell Al Fansome)

Images have been the bane of DXers for decades. They often manifest themselves as a particularly strong signal that is picked up on other frequencies. With an analog receiver, these frequencies are often offset from the actual frequency by the IF frequency of the receiver. With VHF/UHF radios and scanners, this is often 10.7 MHz, or close to that. In the case of the SDR-14, the image was located at an offset equal to the I/Q data rate. It was probably being heard on 6558 kHz (6754 kHz – 196 kHz) as well.

If you’re hearing an unexpected signal, one suggestion is to try another radio, ideally one with a different IF frequency. If you don’t hear the signal on the second radio, then it is most likely an image. Or your other radio is broken. But it’s probably an image. Ask another DXer if they can hear it, as well.

There’s a ham in Erie, PA that has been harassing the local club that runs a 2 meter repeater with claims of interference to the VHF marine band. The FCC has investigated, and found no interference. Multiple hams have contacted the Coast Guard and they have not had any interference issues. The only person who reports interference is the previously mentioned ham, who lives a few hundred yards from the building housing the repeater. I’ll close by noting that the VHF marine band is about 10.7 MHz above the 2 meter band frequency used by the repeater – 146.610 MHz.

Wolverine Radio SSTV

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Shortwave pirate radio station Wolverine Radio was on the air last night, with their typical excellent signal, excellent audio, and excellent programming. As is often the case, they finished their show with a Slow Scan TV (SSTV) image. SSTV is a way of sending an image using audio tones.

Here’s a video of the image, while it was being received. As you can see, it takes about 2 minutes to send a single image. Hence the name Slow Scan TV.

Here’s a larger video image, if you don’t mind rotating your head to watch it:

The image was decoded using the SSTV App for the iPhone, iPad, and iPod Touch which I will now shamelessly mention is

Here’s what the transmitted image looked like, by the way:

New version of SdrDx available, now for Windows also

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There’s a new version of SdrDx, the free app for RF Space SDRs (SDR-IQ, SDR-14, netSDR, etc): http://fyngyrz.com/?p=915

This version includes a lot of new features, including recording I/Q data directly to disk, so you can then play it back. Think of it as a VCR. You can, for example, record the entire 43 meter band (6800-7000 kHz or so, depending on your SDR model) and then go back later and run the I/Q recording back through SdrDx again. It’s awesome! Previously I’ve had to run SpectraVue under vmware to do this, now I can do it natively on the Mac.

I use a program I’ve written myself, that reads in the I/Q data file, and plots a waterfall for the entire file. I can then selectively demodulate what signals I want. I can record all of 43 meters overnight, then check in the morning to see who was on, and listen in. I don’t miss anything, nor do I have to choose if there’s two, or even three pirates on at the same time. I can listen to all of them. At some point I may release this for others to use (Mac OS X only) but it’s still pretty crude right now.

There’s lots of other new features and improvements to SdrDx, so if you have an RF Space SDR, go download a copy to try out.

GPS Disciplined 10 MHz Reference

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Some time ago, I wrote about the Rubidium reference that I connected to SDR. The reference supplies a very stable and precise 10 MHz reference clock to the SDR, so that the sample rate does not drift. Drift in the sample rate causes drift in the received frequency, much like drift in the various oscillators in a conventional radio causes drift.

Just today, I replaced the Rubidium reference with a GPS disciplined reference.

Here’s what I got:

The reference itself is the box in the center. To the right is the power supply, to the left is the antenna.

A GPS disciplined reference or oscillator uses timing signals from the GPS satellites to control,or “discipline” the oscillator built into the reference using a tracking loop. The 10 MHz output is continuously adjusted to keep it at the correct frequency, usually by making very small adjustments and using long time constants (averaging periods), typically around 100 seconds or more.

The 10 MHz output from the reference connects to an input on the netSDR. Internally, that 10 MHz signal is used to produce an 80 MHz clock that is used to drive the A/D sampling.

Here is what the inside of the reference looks like:

Here’s a plot of WWV on 10 MHz:

I believe the frequency shifts you see are due to doppler effects in the ionosphere.

Now I can figure out exactly what frequency Captain Morgan is on.

Excellent 43 mb Propagation, 10/11 mb Operators Put On Suicide Watch

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Old Sol has been quiet lately. Far too quiet for the 10 and 11 meter band guys. As I’m typing this, the solar flux is back into double digits, at 95. The Sun Spot Number (SSN) is officially 24, but you need to squint real hard to actually see any sunspots:

Sunspot SunSpeck group 1452 has pretty much rotated out of view, taking the meager solar activity we’ve had with it.

The NOAA/NASA/Space Weather prediction boys promise that we’re still a year away from the peak of cycle 24, and activity will increase.

Go up. Yes, it will go up any time now, just you wait. Hey! Look over there! Global Warming!

Meanwhile, back in the real universe, the background x-ray flux is at B1 levels.

So what does all this mean for us DXers? The lower solar activity has several major effects. First, the highest frequencies that can be propagated are lower, in many cases much lower. During a solar cycle maximum with high activity, the higher bands are often open 24 hours a day. With the lower activity we’ve been having, this is not this case. Yes, 10 meters is still open at times, but not nearly as much, or with the good conditions that have been experienced in the past. So operators and listeners need to move down to lower frequencies.

The foF2 frequencies are correspondingly lower, which means that a given band (including 43 meters) will go long earlier in the evening. Operators may want to adjust their schedules accordingly, and consider transmitting a little earlier to reach a semi-local audience. OTOH, they’ll end up reaching more distant listeners earlier in the evening as well.

Second, D-layer absorption is lower, due to decreased x-ray flux from the Sun. This means that lower frequencies are not attenuated as much, which is a good thing, since in many cases that’s all that is propagating. The last few days, I’ve been hearing 48 mb (6 MHz) Europirates fade in as early as 2 hours before local sunset. And once the Sun does set, their signal levels increase to really strong levels. Likewise, US pirates such as Wolverine Radio have been reported across the US and into Europe with incredible signal levels.

Third, the lack of major solar flares and coronal streams affecting the Earth means that geomagnetic conditions have been very stable. No geomagnetic storms means stronger signals, and less fading.

The net result is that reception conditions for 43 meter band pirates has been extremely good lately. Lots of operators and listeners have been taking advantage of the excellent conditions, loggings are way up.

There is a coronal stream expected to start impacting the Earth around the 13th or 14th of April, so we’ll have to see what effect, if any, that has on conditions. Until then, enjoy the great propagation!

SdrDx – Software Defined Radio (SDR) App for Mac OS X

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Software Defined Radios (SDR) have revolutionized the HF radio monitoring hobby. While most of the SDR manufacturers only offer Windows versions of their SDR application software, there are many third party solutions for other operating systems.

I use Macs, and there’s a great SDR app called SdrDx. It is based on the open source CuteSDR program (which fortunately uses the more permissive BSD license rather than the overly restrictive GPL license, allowing a much wider use of the code). SdrDx is free to download and use.

SdrDx works with all SDRs made by RF Space. I believe it may also work with some soundcard based SDRs, although I have never tried it that way.

As obvious by the screenshot (from a 24″ iMac) there’s a lot of controls. Besides the typical waterfall and spectrum displays, there’s also controls for memories and notch filters, as well as the ability to control the various AGC and noise blanker settings.

There’s a readme file that comes with the download, and recent versions of SdrDx have an optional tooltip display, so you can hover the cursor over a control to find out what it does.

The author of SdrDx is actively developing it, and has added quite a few features based on user suggestions. If you run Mac OS X, and are looking for an app to control your SDR, SdrDx may be the way to go. Download a copy and try it for yourself.

Ops may wish to avoid 6950 kHz

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I’ve noticed LINK-11 (TADIL – Tactical Digital Information Link) transmissions in the 6940-6950 kHz region the last day or two. Operators may wish to avoid 6950 kHz, and perhaps even 6955 kHz, especially while these transmissions are occurring.

I have no idea where these transmitters are located, but if I had to guess based on propagation characteristics, I’d say maybe Canada or out in the Atlantic.

LINK-11 is operated by the US military. I’m pretty sure you don’t want to interfere with it.

Global Pirate HF Weekend Results So Far

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While conditions may not have been spectacular, I was able to hear a lot of stations. All heard with a JRC NRD 545 receiver and my 635 ft sky loop antenna.

Here’s what I’ve heard so far, all loggings reported to the HFUnderground.com message board.

Stations Heard UTC March 30:
Trans Europe 15020 AM 1420 UTC
Mike Radio 21455 AM 1356 UTC
Fox Radio 6308 USB 0010 UTC

Stations Heard UTC March 31:
Mustang Radio 15000 AM 1115 UTC
Trans Europe Radio 15020 AM 1125 UTC
Rave on Radio 6925 USB 1215 UTC
Radio Underground 15050 USB 1242 UTC
Radio Spaceshuttle 15845 USB 1223 UTC
Radio Underground 15850 USB 1302 UTC
Radio Paranoid 15030 AM 1134 UTC
Baltic Sea Radio 18950 LSB 1346 UTC
Radio Scotland 15060 AM 1400 UTC
Radio Mustang 15020 AM 1415 UTC
Cupid Radio 21460 1435 UTC
Cupid Radio 15070 1523 UTC
Radio True North 21850 AM 1529 UTC
Undercover Radio 15050 AM 1538 UTC
Radio True North 15520 AM 1623 UTC

Global Pirate HF Weekend March 31 – April 1

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This is a great opportunity to hear a lot of Europirates!

Global Pirate HF-Weekend will be 31.3. – 1.4.2012. ( from http://hkdx2.blogspot.ca/ )

Be sure to visit either the #pirateradio IRC chat or Iann’s Chat while the event is taking place, to get current information on what stations are active.

1) RADIO SCOTLAND, Holland- 15.060 MHz – AM – 200 W
Saturdaymorning 08:00 – 10:00 h utc.
Saturday afternoon 14:00 (or 14:15) – 15:00 h utc.
Sundaymorning 09:00 – 11:00 h utc.
LIVE WEB-CAM: http://www.radioscotland.nl/Webcamrsi.html

Frequency 15.050 – 15.065 MHz, if 15.060 is occupied.

2) TRANS EUROPE RADIO, Holland – 15.000 – 15.100 MHz – AM – 65 W
Will be active during Saturday and Sunday morning and afternoon
on 19 mb.

3) BALTIC SEA RADIO, Scandinavia – 21.485 MHz – USB – 80/150 W W
On Saturday starting 08.00 and again 13.00 utc
On Sunday starting at 09.00 utc.

4) RADIO BORDERHUNTER, Holland – around /15 MHz/ 21.5 MHz – AM
More information later for dates and frq’s

x) OLD TIME RADIO, Scandinavia – 15.009 MHz – AM – 50 W
Short test was planned but cancelled for this weekend.

5) RADIO BLACK BIRD, Holland – 19 mb – AM
No frequency or time information yet.

6) WR INTERNATIONAL, England – 12.257 MHz – AM – 35 W
WR is on the air every Sunday from 08.00 – 11.00 utc.

7) BALKAN RADIO INTERNATIONAL – ??? MHz – AM –
New station from Balkan area. The station has new transmitter and
let’s hope it will be on air for this weekend.

8 ) RADIO SPACESHUTTLE, Scandinavia – 15.845 MHz – AM+SSB – 200 W
Saturday and Sunday some transmissions between 07:00-16:00utc on
15845 kHz (or nearby). AM and SSB (changing time to time)

9) FREE RADIO NOVA, Holland 15.070 MHz – AM
Sunday 1.4.2012 starting at 08.00 utc.

10) MIKE RADIO, Holland – around 21.500 MHz – AM
Not 100 %. 21.500 or 21.850 MHz.
Antenna tower still down for the winter.

XX) RADIO BLACK ARROW, Holland – 21.490 MHz – AM
Transmitter broken week ago – Possibly not on air

11) RADIO FOX 48, Scandinavia – about 15.092 MHz – USB – 300 W
Saturday 14.00 – 16.00 utc.

12) CUPID RADIO, Holland – 21.460 MHz (or 15.065 MHz) – AM
Saturday 31-3 euro afternoon broadcasting towards the U.S.A freq 21.460 mhz [when the band is down 15.065]
Sunday 1-4 starting at 08:00 utc till 10:00 utc freq freq 21.460 mhz [when the band is down 15.065]
Sunday 1-4 euro afternoon broadcasting towards the U.S.A freq 21.460 mhz [when the band is down 15.065]
Loads of sstv pictures will be send out during the broadcast.

13) MUSTANG RADIO, Holland – 15.000 – 15.100 MHz – AM – 50 W
Again new participant! More info later!!

14) RADIO LATINO, South Europe – 15.000 – 15.100 MHz –
26.100 – 26.200 MHz – AM – 40 W
Salsa mix-programme (30 min) on early morning on Saturday and Monday
at 06.30 – 07.00 and 07.30 – 08.00 utc! Progamme will continue longer if possible.
-26.100 – 26.200 MHz (in the morning, if propagation helps)
-15.000 – 15.100 MHz (in the evening, if morning propagation is bad)
More info and realtime-info on the web-page: http://radiolatino.bigbig.com/
E-mail: radiolatino@live.com

15) RADIO UNDERGROUND, England – 15.000-15.100 MHz -USB – 80 W
More exact frequency and times later, also 21 MHz is possible.

16) FREE RADIO VICTORIA, Holland – 21.880 MHz – AM- 50 Watts
On Sunday 1/4/12 from 08:00 ….. 10:00 UTC on the Dipole intend for Scandinavia and the Mediterranean Sea.
On Sunday 1/4/12 from 11:00 ….. 13:00 UTC on the Vertical ant. intend for overseas country,s .

17) RADIO TROPIQ, Central Europe – Many frequencies – AM 50 W / LSB – 80 W
Saturday
15.00 – 15.30 UT 15.050 MHz
16.00 – 16.30 UT 11.450 MHz
18.00 – 18.30 UT 9.950 MHz
Sunday
08.00 – 08.30 UT 18.205 MHz
09.00 – 09.30 UT 9.950 MHz

North America
18) Radio True North – 15.460 MHz (200 W) or 21.850 MHz (40 W)- AM
On air from 14.00 – 23.00 utc.
Also possibly on air on 6.925 or 6.950 MHz around at 02.00 utc

OUT OF HF-FREQUENCIES:
19) COOL AM RADIO, Holland – 10 Watts mobile – 6925 or 6940 kHz
This station is NOT HF-station because it uses 42 mb but I
took this in because it is special 10 W mobile!!

PIRATES – ATTENTION!
Info of free frequencies can be found here:
http://www1.m2.mediacat.ne.jp/binews/bia12.txt

BASIC SCHEDULE

1) European MORNING 08.00 – 12.00 UTC from Europe to Asia/Japan/Oceania.

2) European AFTERNOON 12.00 – 16.00 utc from Europe to North America and vice versa.

3) European NIGHT 22.00 – 24.00 UTC from North America to Asia/Oceania.