Friday, June 22, 2012

The SDR Chronicles (#4: Getting Down to Business)

Several interesting things:

1. This location is prone to overload from several nearby AM broadcast stations.  Obviously any SDR with the typical barn door front end is going to have issues with this.  The Excalibur Pro has a hardware MW filter that rolls off the RF input starting around 2 MHz, and it works.  Without it, the noise floor below 4-5 MHz is mostly broadcast intermod and general crud.  With it, the noise is the usual HF static.

2. There is another hardware RF filter which can do passbands.  This can be cranked in to also roll off above your tuned frequency. This is not needed here, yet anyway, but if you have a 27 MHz ratchet jaw or local ham DX ace with "maximum legal power," I can see where it would come in handy.

3. I had no interest in DRM until I got this radio. Now, I have Radio New Zealand International going in beautiful, noise-free audio while I write this.  The Excalibur Pro actually comes with a DRM demodulator, but one needs to pony up a non-trivial sum of money (around $70 US at current Euro exchange) for a license to use it. Once this is done, the DRM works just fine on strong signals.

As with any DRM receiver, audio dropouts start occurring when the s/n ratio displayed by the demodulator drops below about 15 dB. This setup here is actually good down to about 12.5 dB.  Below that, you will hear a brief reverb effect sounding like an old Fender amp, followed by silence.

4. "Dream," a free DRM demodulator program from Source Forge, works very nicely with the Excalibur Pro. I don't know if you can get it to work just using "stereo mix" or the "virtual audio cable." I'm using WinRadio's "Virtual Sound Card," aka "Digital Bridge," another paid add-on.  Clicking "IF" sends out a real IF output, user adjustable to the necessary 48000 bps, and centered on zero with stereo I and Q.  After this, Dream needs to be started after the Excalibur software, and using the following command line:

C:\[path]Dream.exe -c 5

where [path] is the usual full path to wherever Dream.exe lives on your box.  This puts it into the proper config to handle this I/Q mode.  The audio, at least on this computer, has a bit more midrange punch than on WinRadio's decoder, but it is also more prone to dropouts and affected a LOT more by fading.

5. One last thing about DRM: it will NOT work with the noise blanker on.  I found this out the hard way.  You'll never get above a 9.5 dB s/n with it on, but you'll rarely get that low with it off.

6. The manuals make a considerable fuss over something called the XRS Variable.    This is a Windows environment variable which tells the software where to install and look for plugins.  If it doesn't match the path shown in the registry, plugins won't work.

No matter what I did, this variable showed up as null, even though the path in the registry was correct.  The "G3 Diagnostic Tool" ( a free download from WinRadio) would pick this problem up, but the "XRS Repair" would not fix it.

DO NOT re-install the driver and application software, because this is a pain in the butt and unnecessary. The real fix is actually well explained in a document buried deeply on the WinRadio web site. I might as well save you the time, however.  Here goes.

You need to find out how to set "environment variables" on your particular version of Windows.  On mine, it's right click on "computer," then take the "Advanced" tab and click the box labelled "Environment Variables."  Then create one called XRS_PLUGIN_PATH, in both user and system variables, and set its value to whatever the diag tells you it says in the registry.  Here, it's

C:\Program Files (x86)\WINRADIO\PLUGINS

and case does not seem to matter.  I copied and pasted the text right out of the G3 diag.  Voila.  Now plugins install to the right folder, and the software finds them, and they work as well as they're ever going to.  "Presets" is a useful little plugin.

There's more, but this is getting pretty geeky if you don't have one of these radios.  And the fun continues......

Thursday, June 21, 2012

Night of Nights XIII Is Upon Us!

From Richard Dillman of MRHS:

NIGHT OF NIGHTS XIII - SAVE THE DATE

12 July 1999 was a sad day for many of us. We knew it was coming but when the end finally arrived it was a shock. I was there.

It was the supposed last day of Morse code. The final sign off took place at a remote station on the Pacific coast. Women attending the event were dressed as if at a funeral. Grizzled, hard bitten old men, the kind you wouldn't mess with in a bar room, had tears in their eyes as the last message was keyed out to the world at 0000 gmt. And then there was silence. It was just beeps in the air. But that's how much Morse code means to the men and women who made the profession of radiotelegrapher one of honor and skill.

But the prediction of the death of Morse code was not to be fulfilled. On that day the Maritime Radio Historical Society was born. On that day we began plans to restore a Morse code radio station - the famous KPH. One year later we held the first "Night of Nights" when not only KPH but other coast stations appeared once again on the air. Every year since we have commemorated that date by returning these stations to the air and thereby, we hope, honoring the men and women who came before us.

Join us this year for Night of Nights XIII. See and hear a real Morse code coast station in full song. Mingle with the pioneers who were the men and women of the airwaves.

Or, if you can't join us in person, join us on the air. KSM and, we hope, KPH and KFS will be in action (to be confirmed - watch our Web site for updates). K6KPH will be open to calls from amateur stations.

When: 12 July 2012 - Doors open at 3:00pm, first transmission at 5:01pm (0001gmt)
Where: KPH receive station, 14700 Sir Francis Drake Blvd, past the oyster company and G Ranch
Information: info@radiomarine.com or 663-8982

Light snacks will be served.

VY 73,

RD

Monday, June 18, 2012

Mexican Military List Grows

More frequencies have been discovered for the Tadiran radios in use by the Mexican Navy.  Mike Chace-Ortiz reports that this system has actually been in use for some time.

There are also two frequencies where the older Harris AVS voice scrambler, aka the "Hooter," is still in use.

Here's the list of frequencies heard here:

4595.0    Harris AVS
4617.5    Tadiran scrambled voice
4625.0    Tadiran
4650.0    Tadiran
4675.0    Tadiran
4700.0    Tadiran
4707.0    Tadiran
4730.0    Tadiran
4810.0    Stanag 4285, continuous and message mode
4820.0    Tadiran encr 110A and 2-tone data mode
4865.0    Tadiran clear voice, then 110A
4880.0    Tadiran clear and scrambled voice
4885.0    Tadiran encr 110A & scrambled voice
4890.0    Tadiran encr 110A & clear voice
4895.0    Tadiran rekey/sync sequence and buzzy mode
4900.0    Harris AVS
4910.0    Tadiran rekey, occasional short PSK data bursts
4915.0    Tadiran selcal, no traffic
4920.0    Tadiran encr 110A
4930.0    Tadiran

Mike has heard others, as low as 3808 kHz USB, and as high as 19105.  These have so far not been heard here.

Friday, June 15, 2012

The SDR Chronicles (#3: Discoveries)

I'm really starting to get the hang of the Excalibur Pro.

One very useful feature is the waterfall palette adjustment.  This is a bit different than the ones you've seen.  The two adjustments are for "bottom" and "gravity."  The first sets the low end of the color scale, while the second defines the place where the colors change the fastest.  These interact, and take some fussing, but they are useful when you need to pop out weak signals, or if you just want a brighter display.

While investigating signals around 4 MHz, I ran across some modes I hadn't heard before. According to Mike Chace-Ortiz, our digital editor and authority on such things, these are Tadiran radios.  He suspects Mexican military, and I do too.  That particular agency can really go through modes.

Given the disappearance of all their ALE nets with the cute call signs, a new Mexican military radio network is something of a major discovery here.  For various reasons, the confidence is high that these are indeed the people making all their latest weird noises.   The clear voice sounds like the way they train their operators, and also some stations are still using the older "Hooter," an analog voice scrambler made by Harris.

It appears that the new (at least for me) equipment has a number of selectable waveforms, best tuned in USB.  Nearly everything starts with a short, 1000 hertz beep, making tuning simple.  After this, one hears clear voice or several obviously encrypted waveforms.

These latter have the payload signal on the low end, but also include various lengths of high-pitched data signalling in 2-4 narrow audio bands centering around 2800 Hz. One is obviously a kind of vocoder-ish voice scrambling, while another is just the high band by itself. A third is a high-band "turkey call" beginning with the 1-kHz beep, and apparently some kind of crypto key/sync information, followed by a PSK waveform that detects as MIL-STD-110A. Being encrypted, it of course always errors out.

The SDR waterfall allowed rapid identification of these signals, and the recording feature made close analysis of the frequency range possible.  So far, all this activity is between 4.5 and 5 MHz, nearly always in 5-kHz channels.

Frequencies identified so far are:

4595 4617.5 4625 4820 4865 4880 4885 4890 4895 4900 4910 4915 4920 4930.  The 4617.5 does not fit this convention, but indeed that was the right frequency.

The speed with which all this data was gathered is a major indication of the usefulness of the SDR in the utility DX pursuit.  I'm sold.

Wednesday, June 13, 2012

The SDR Chronicles (#2: First Light)

With the USB issue sorted out, it was time to get down and hack some serious radio with the slick Excalibur Pro.

People have said good and bad things about the user interface.  Personally, I love it.  I'd actually downloaded and run the Perseus and WinRadio software test versions as part of my agonized decision making.  I found the WinRadio software to be more usable on my graphics production monitor with its large screen and small font sizes.   Something like this is important with a tool as intensive as an SDR, which serious users will undoubtedly stare at for hours at a stretch.

The interface has three major displays. Top left is the DDC spectrum, top right is the demodulator spectrum, and across the entire bottom is the spectrum analyzer. This third one displays the entire range of the analog-digital converter, from the low-frequency band to either 30 or 50 MHz depending on configuration.

It really is rather compelling to turn on the waterfall display, and watch all of HF go by at once.  Chirpsounders make diagonal lines across the entire band, and often multiple reflections appear and disappear.  OTHB radars make little short squiggly lines that change frequency.   CODARs show up as closely spaced diagonal sweeps, making it a snap to measure their frequency ranges.   A mysterious entity centered on 24 MHz produces a whole band of little bursts with a frequency distribution resembling the statistical bell curve.  Spread spectrum?

In practice, of course, one sees a lot more detail with this display zoomed in.  Being an SDR, it is of course clickable, taking you right to interesting spots.  So are the other two plots.

Returning to the spectrum display, I clicked a nice spike around 22 MHz.  With some tweaking in the DDC window in waterfall mode, I got centered on an obvious broadcast station.  Its carrier showed as a vertical line, with symmetrical sidebands going out both ways.  It was Radio Australia.

Somewhat later, another interesting spike showed up in 75 meter amateur, where voices usually display as the intermittent RF bursts of lower sideband emission.  Yes, it was AM.  In fact, the voice was familiar.  My new SDR had apparently found a local ham buddy on that band's AM frequency.  He was discussing his new SDR (a Flex), which he'd picked up at Dayton.

Ultimately life intervened, and I had to tear myself away from the Excalibur Pro.  By then I had the user interface pretty much wired, and I was getting used to the best ways to unleash the awesome performance of this little box, with its vertical filter slopes (more on these later), amazingly low noise, and generally snappy performance.

It is clear that this radio is a tool.  You do not listen to it as much as you wield it, like King Arthur with his magic sword.  Congratulations to WinRadio for making a product that really does live up to its initial hype.


Tuesday, June 12, 2012

The SDR Chronicles (#1a: Update)

Richard at WinRadio e-mails the following:

If you have a very new PC with USB3 ports, try connecting to a different
port, preferably USB2 because hardware /driver support for backward
compatibility of USB3 varies between manufacturers.

This certainly explains why the radio worked properly on the laptop, which only has USB 2.0.  It also explains why it worked when I put it back on the big computer.  Just for the sake of testing one new variable, I had indeed tried a different USB port, and one known to be 2.0 only.

And so we have cleared that up.  I figured it was something to do with the USB, since there have been other issues with other products used for radio.  Obviously, this is not a bug in the Excalibur Pro, which in fact is living up to its advertising.

Monday, June 11, 2012

The SDR Chronicles (#1: Installation)

Many months ago, I decided to add an SDR (Software-Defined Radio) to my array.  After this, I spent altogether too long agonizing between the venerable Perseus and the new Excalibur Pro.

Both of these are DDC (Digital Down-Converter) radios.  Essentially, an untuned RF front end goes to an A/D converter, and is down-converted by a mathematical algorithm for output over a standard USB 2.0 cable.  What used to be the IF strip, where the real action in a superheterodyne receiver goes on, is now done by software.  What used to be the detector stage is now a digital demodulator, making waveform changes a snap. Finally, the result goes to the computer sound card for D/A conversion into audio for the computer's speakers.

The Perseus is an established product, a bit old, but with a large and dedicated user base which shares many great things that various smart people have learned to do with it.  The slightly more expensive Excalibur Pro was vapor until about a year ago, and its userbase is tiny by comparison, but anyone who ever tried it said it was a darn good radio.

Finally, I went with the Excalibur Pro.  I think it's the broadcast audio that finally tipped the scale, though obviously nothing using computer audio will ever match the soul stirring roar of the R-390 through a good stereo system.  Still, it is clean and non-fatiguing, which is more than I can say for most of the better radios used by utility DXers.

My nice new radio arrived last Friday, and was summarily unpacked. It's a neat looking little metal box, covered in a futuristic looking material that looks pretty indestructible.  The antenna downlead, snap-in USB connector (supplied), and DC power connection are on one end, which is considered the back.  Extra points to WinRadio for using a linear power supply rather than a wall wart.

The front has a main power button and a minimalist blue LED.  Once you power up,  the LED blinks in a fair semblance of Morse code to show the radio's state of readiness.  "S" means you're connected and waiting for the software to start.  A somewhat elongated "A" means you're good to go.

Installation is just a matter of following steps.  Install the software, cable up the radio, turn it on and let Windows find it.  Let it install the driver, then connect your antenna through the BNC-SMA adapter supplied, and light up the software.

At this point, there should be spectrums dancing and audio happening.  The box was factory set to 10 MHz WWV.  I should have had time.  Time with latency, but time.

Nothing.  No dancing spectrums, no audio, no nothing.  An hour or so of various troubleshooting steps got nowhere.  ????

I was damned if I'd send my nice new box back to Grove before trying it on another computer.  And so I did.  Same process, exactly, except that when WinRadio's app was started, the radio gave a little relay click and WWV lit up the screen and speakers.

At last, I had found time.

The radio was connected back to the big computer, a 6-core 3.2 GHz liquid-cooled production machine with the horsepower to do some serious radio processing.  This beast was going to be its friend, one way or another.  For whatever reason, this time it was.  The radio gave the same little relay click, and everything's worked great since.

Computers.  Can't live without 'em, can't live with 'em.

(To be continued.)