All India Radio DRM: Dan notes two simultaneous feeds

All India Radio (AIR) Headquarters in Dehli, India. Photo courtesy of Wikipedia.

All India Radio (AIR) Headquarters in Dehli, India. Photo courtesy of Wikipedia.

Many thanks to SWLing Post contributor, Dan Srebnick, who writes:

While DRM (Digital Radio Mondiale) has long been pronounced DOA (dead on arrival), All India Radio seems to be taking it pretty seriously. Here’s a screenshot of not one, but two simultaneous feeds going out over the same 10 kHz wide 40 meter frequency (7,550 kHz) at 2027 UTC today. The signal on my Perseus was just a tad under S9+5db using my ham band Alpha Delta DX-CC antenna.

image001So what’s the twist, aside from the 2 feeds on 1 frequency? Even at +5 over S9, the feed was only strong enough to occasionally flutter in with some decoded audio. Mostly, it was silence.

[I had] about a 98% successful decode by 2051 UTC when the signal rose to S9+10 db. I could switch between streams by clicking channel button within Dream!

Dan wrote the message above yesterday, I asked him if he could record AIR  today and he kindly sent the following:

AIR DRM recorded today with announcements @ 1930 UTC. Some dropouts as a
great example of the dropout/echo effect heard on DRM when signals are quite
strong enough. This decode was done at S9 signal strength.

Dan actually calls the DRM dropouts, the Max Headroom Effect.”  That is the best description I’ve ever heard, Dan.  Thanks for sharing your notes and recording!

How to decode maritime broadcasts in RTTY, Sitor B, and NAVTEX

(Photo Credit: NOAA)

(Photo Credit: NOAA)

Many thanks to SWLing Post contributor, Mario Filippi (N2HUN) for the following guest post:


Maritime Broadcasts in RTTY, Sitor B, and NAVTEX.

By Mario Filippi, N2HUN

(All photos below are courtesy of the author. Click each image to enlarge.)

Non-voice high seas weather broadcasts and safety messages to mariners can be found by spinning your VFO dial to 8.472 MHz USB courtesy of WLO from Mobile, AL, which provides these transmissions continuously. Here on the East Coast it is received with regularity due to it’s strong signal.

Those of you who are neophytes to RTTY or just want to dabble then this is the place to be to try your hand at an old and venerable digital mode. The RTTY (RadioTeleTYpe) parameters used by WLO transmissions are 45.45 bauds, 170Hz shift. These are most commonly used by amateur radio ops too. If you’ve roamed the bands for RTTY signals you’ll find that most are encrypted with a few exceptions, one of which is WLO which is transmitting continuously.

Tabletop SW radio set to WLO; SignaLink USB links radio to computer for decoding.

Tabletop SW radio set to WLO; SignaLink USB links radio to computer for decoding.

On 8.472 MHz you’ll receive weather information from different latitude/longitudes, along with other pertinent information to mariners such as high seas pirates (not radio pirates!) and naval maneuver areas that are important for ships to avoid. It makes for interesting copy.

To decode RTTY signals you’ll need a shortwave receiver with a BFO (Beat Frequency Oscillator), a way to pipe your radio’s audio into your computer’s sound card, and decoding software. There are several RTTY software packages out there, free, and my favorite is MMTTY. More info on MMTTY is at: http://hamsoft.ca/pages/mmtty.php . Old timers will find this software a snap to use, but newcomers will have to fiddle with the controls to get the decoding going. Below is a snapshot of MMTTY decoding a typical weather broadcast.

MMTTY dashboard with WX info. Cross-like indicator on upper right aids in tuning signal.

MMTTY dashboard with WX info. Cross-like indicator on upper right aids in tuning signal.

Another software available for decoding RTTY is Fldigi. Again, you’ll have to input the correct RTTY parameters such as baud rate and shift into the program along with adjusting your VFO carefully. It takes practice, but when the decoding is successful you’ll see Fldigi doing it’s thing as shown below. Both MMTTY and Fldigi have waterfalls displaying a visual image of the received signal. With practice you’ll be able to distinguish the different common RTTY shifts just by looking at the waterfall.

Fldigi in action with split screen; RTTY text above, waterfall below.

Fldigi in action with split screen; RTTY text above, waterfall below.

Now to Sitor B (Simplex Teletype Over Radio Mode B), another non-voice mode we can use to decode WLO transmissions. Sitor B sounds a lot like RTTY to the human ear, but requires different decoding software. WLO transmits weather information via Sitor B immediately after RTTY transmissions, switching back and forth, which makes for even more fun! Software that decodes Sitor B is available on the ‘Net as free downloads. One is MultiPSK, the other is YaND.

I like YaND (Yet another Navtex Decoder) which is used to decode NAVTEX (Navigational Telex) transmissions commonly found on 490 KHz and 518 KHz, but it works well for decoding Sitor B. There is a difference in the way messages are processed in NAVTEX versus Sitor B and for further information perform a Google search. But the fastest and easiest way to decode Sitor B transmissions from WLO is to fire up YaND. Below is a recent NAVTEX HF broadcast capture.

WLO HF WX broadcast for NE Gulf on 1/18/16 .

WLO HF WX broadcast for NE Gulf on 1/18/16 .

Well, hopefully some of you will be inspired to check out maritime weather/safety information found on WLO using RTTY/Sitor B/NAVTEX software. However, RTTY can also be found on the ham bands and on shortwave frequencies. Several RTTY stations from Germany are found on frequencies such as 11.039MHz and 14.467MHz. Their weather information format is quite different and will give you an idea of European weather conditions and allow you to practice your German. When not sending weather info they run a RTTY message loop below at 50bauds/425Hz shift.

German RTTY station with message loop. Deciphered via MultiPSK.

German RTTY station with message loop. Deciphered via MultiPSK.

In closing, make sure to also check out the NAVTEX broadcasts found just below the AM broadcast band on 490 and 518 KHz; using YaND or MultiPSK you’ll be able to receive these transmissions, but remember you’re not on HF, you are on MW (medium wave), where signal distances are shorter and present a greater reception challenge. YaND software has a NAVTEX broadcast schedule built in as seen below; you have to identify your specific NAVAREA or navigational area, then look at the times and frequencies to determine when to listen in. My QTH is in NAVAREA 4. Lots of interesting information is passed in these NAVTEX transmissions so listen in and have fun!

YaND NAVTEX schedule for various NAVAREAS.

YaND NAVTEX schedule for various NAVAREAS.

NAVTEX on 518 KHz from station VAR-9, New Brunswick, CAN. Messages begin with “ZCZC.”

NAVTEX on 518 KHz from station VAR-9, New Brunswick, CAN. Messages begin with “ZCZC.

Mario Filippi (N2HUN), is the author of this post and a regular contributor to the SWLing Post. Click here to read Mario’s guest posts.

Bill recommends the Signal Identification Wiki

31meterband-waterfall

Many thanks to SWLing Post reader, Bill, who shares a link to this Signal Identification Guide:

http://www.sigidwiki.com/wiki/Signal_Identification_Guide

Curious if any readers have been using this guide–seems like a convenient resource to ID those numerous signals on the bands. Entries show what each signal looks like on a spectrum waterfall display and provides audio clips.

Thanks for the tip, Bill!

A Review of Multipsk Software for Digital Modes and More

http://ak3q.com/wp-content/uploads/2016/01/MPSK2.jpg

Over the last year or so I have been using a really full-featured digital mode software called Multipsk, and it has become my go-to software for most digital modes. Back in September 2015 I wrote an extensive review of the software for The Spectrum Monitor (TSM) which Owner/Editor Ken Reitz has graciously allowed me to post on my blog at All Things Radio. Thomas has written numerous articles for TSM, and will attest to its emphasis on so many aspects of the radio hobby. If you are not a subscriber already you really do not know what you are missing!

The program boasts over 75 modes, not counting some of the many sub-modes or variations, and new modes are being added all the time. There is a free version and a registered version, with the paid mode costing around $45 (U.S.) The free mode will handle a lot of really great modes, but I confess, it was the additional “professional” modes which really made purchasing the registered version a must for me. Whichever way you go, you will not be disappointed. As I have noted on my blog and in the article itself, I consider the registration fee some of the best money I have ever spent for computer software.

As an added bonus, the free or registered version can be run on as many computers as you have in your home, and multiple instances of the program can be run on the same computer provided they are in separate directories. This is a great feature, and it means there is basically nothing going into the Windows registry file–the program runs right from the directory. My only problem is not having enough antennas to have as many instances of the program running as I would like!

I hope you will take time to read my review and then get the program–I think you will be suitably impressed as I was! (I have it running on XP machines through Win10, so compatibility should not be an issue.)

Robert Gulley, AK3Q, is the author of this post and a regular contributor to the SWLing Post. Robert also blogs at All Things Radio.

Alexander reviews the Avion AV-DR-1410 DRM receiver

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Many thanks to SWLing Post contributor, Alexander (DL4NO), for the following review of the new Avion DRM receiver:

A review of the Avion DRM receiver

by Alexander von Obert (DL4NO)

The Avion AV-DR-1401 DRM receiver has appeared on the SWLing Post before in a previous review.

Amazon India does not sell the Avion outside of India. As it happens, I found someone who was willing to buy it for me and bring it with him from India to Germany.

The first impressions were quite disappointing. This feels more like a prototype, not a polished product:

  • The power supply produces lots of interference and runs quite hot. Unless I find another power supply, I can either charge the battery or listen to the radio.
  • The handle rattles. Such things often are symptoms for the whole product.
  • The firmware fails in many ways: update errors of the display, very confusing user interface.
  • No acceptable field strength indicator, especially in DRM until a signal is decoded. If you have a selective antenna you need to switch to AM to tune it. And then you tune it by ear or by numbers. No bar of any kind.
Avion AV-DR-1410 DRM

Radio Romania

Radio Romania produced very good signals this evening in southern Germany on 41m. But with the built-in antenna, DRM reception was impossible even in my shack directly under the roof. A Degen 31MS selective active antenna indoors enabled sketchy reception of Radio Romania and All India Radio on 41m. Reasonable reception was only possible with my external antenna.

All India Radio

All India Radio

Just imagine why I took the trouble to get the receiver! It is a far cry from what I really wanted: a modern replacement of my trusty Sony ICF7600D from the 1980s. I had to retire it for mechanical reasons after it travelled with me for 20 years.

In India, they might not have the industrial infrastructure they have in China or Japan, but an intensive firmware update is urgently needed. Software is something they are good at in India. Many problems could be solved that way:

  • The volume knob has no stop and must be pressed for a few seconds to turn the radio on or off. A short press could be used to switch it between volume and tuning.
  • A reasonable field strength indicator should be introduced.
  • The remote control does not work reliably.
  • With the “mode” switch I can select AM, FM, or DRM. But I have not found anything that the “band” switch could be doing.
  • The “scan” switch works on FM and puts all transmitters found into the favorites. But neither is that the function I would expect it to do nor does it work on other bands.

From my preliminary tests I fear the unit has massive large-signal problems. For example, I heard distorted signals of Radio Romania on bands where they were not transmitting at all. I use an active antenna but this is the same I use for the DX Patrol or SDRplay RSP, therefore I know that my antenna is not to blame. I also see this as an indicator about the DRM signal of Radio Romania.

I could not help but open the Avion receiver: [the internal antenna worked so poorly, I wanted to investigate].

I must say that the rattling handle was an accurate indicator of production quality.

Inside the Avion

Inside the Avion

See “Inside the Avion” image above (click to enlarge). The back side on the left was originally covered by an aluminum shield. I had to remove it as the wires are quite short–one cannot put the two parts flat on the bench otherwise. You see that they tried to improve the shielding on the right.

AVION internal antenna preamp

Avion internal antenna preamp

See “Avion internal antenna preamp” above (click to enlarge). The circuit board at the lower left corner of the first picture is the preamp for the internal antennas. In the lower left corner is the telescopic antenna connection. The wire here was extremely short–either it broke before and made contact by chance or I broke it when I dismounted the circuit board. At least I did not force it (still a bad manufacturing practice).

If you examine the circuitry, you see very bad practices: C2 directly connects the antenna to the base of Q2. It must be a bipolar transistor considering R3/R4. At least there is DN1 which seems to be protection diodes. On the whole board I can find no inductivities at all. There is absolutely no band limiting.

AVION broken shilding wire

Avion broken shilding wire

See “Avion broken shielding wire” above. The shielding wire had broken from the soldering. That was definitely not my fault. At the yellow isolation, a second wire is connected. That is the wire routed around the backside without any connection. This doesn’t make sense to me.

Avion crushed battery holder

Avion crushed battery holder

See “Avion crushed battery holder” above. The battery holder is fixed together with the aluminum shielding. The worker crushed the lug of the battery holder while mounting the shield. A few other threads were torn, too. A typical case of too much strength.

Avion seems to know about the inherent RFI problems of this receiver, but could not solve them. No wonder I have to use an external antenna.

Perhaps I will replace the antenna preamp with something reasonable.

Otherwise this radio will gather dust here.

Thank you for your report, Alexander–I’m sorry to hear about your experiences with the Avion, especially after the trouble you went to obtaining it.

So far, I’ve heard no truly positive reviews of the Avion AV-DR-1410. Sadly, it sounds like a radio to avoid.

How Bob McGwier used a Cray-2 supercomputer to decode a ham radio transmission heard in Star Trek IV

Startrek4-MoviePoster-SmallIn response to our recent post with a message to us from Star Wars sound designer Ben Burtt, SWLing Post reader, David Guilbeault, comments:

Here’s a similar story that circulated on the Internet around 1990 (pre WEB!). I worked in packet switching at that time and was very impressed with Bob’s achievement (even with a CRAY to work with) .

I reached out to Bob McGwier (N4HY), who is a Facebook friend, and he has kindly given us permission to share his message again here and with a few new comments:


Star-Trek-IV-Cap

Decoding HF packets in Star Trek IV

Originally posted on December 4, 1989 by Bob McGwier (N4HY)

Several months ago, Harold Price, NK6K, challenged me to demodulate what he thought might be HF packets in Star Trek IV.

Chekov-Uhura-Star-Trek-IV

During the scenes where Scotty is valiantly trying to beam both Chekov and Uhura back from the U.S.S. Enterprise, where they have been stealing Nuclear vessel high speed photons, Scotty is having a hard time hearing them.

Scotty-Star-Trek IV

Listen to the audio clip by clicking here or using the embedded player below (target sound is at 5 seconds):

One of the sources of interference is what appeared to Harold to be HF packet. Always being one to rise to a challenge, I took on the job of doing some fancy Digital Signal Processing footwork. Almost from the first I was certain that it must be an HF packet since my very first demodulator attempt clearly revealed flags before the start of a frame and end of frame was also clear. I knew it was HDLC of some variety.

Several things impeded the effort, including Scotty’s voice on top of the packets, some SSB from 20 meters was also nearly on top of the signal. All of this had to be filtered out. I spent an hour of time on the Cray-2 at work and used the fanciest FSK demodulator I could write and I finally had noisy baseband signal plotted on paper in front of me. I did my best to get an integral number of samples per baud as the signal was very noisy, and though the bits could be made out by eye, I could tell that it was going to take another hour of Cray-2 time to get the clock recovered and to make good bit decisions. In a couple of places, HDLC showed me what were clearly bit errors, and these could be done by eye as well.

A Cray-2 operated by NASA. (Source: NASA)

After the filtering, and building a demodulator for the badly mis-tuned signal (almost 900 Hz below), I took the bits to Phil Karn, KA9Q and he decoded the NRZI data and proved beyond a shadow of a doubt that it was indeed an HF amateur radio packet. It was WA8ZCN-0 sending an RR for NR-3 to N6AEZ on 20 meters. I got Bill Harrigill, WA8ZCN on the phone and he agrees that it was probably him.

Thanks Harold for the challenge and Phil for the help.

Bob N4HY

P.S. A Cray-2 is about 50% faster than the fastest Pentium-Pro computer available today.

Again, keep in mind that the message above dates from 1989! This past week, Bob added the following comment when I contacted him:

The Cray Supercomputer on which the work was done was being operated on behalf of the National Security Agency by my research institute.

I received permission to “to test optimal algorithms for software decoding of FSK transmissions” and this was my test case!!!!

That is why Phil Karn was decoding the AX.25 bits by hand. I did not have permission to develop link layer protocol code, though I tried.

A few years later when half the bad guys in the world seemed to be using AX.25 and cheap ham gear I said “See, I told you so several years ago and you didn’t listen”.

I used that transmission in so many different ways I no longer remember them all.

That’s fantastic, Bob, and so great to know the back story on your decoding process! Thank you again for sharing this with us!

Star Trek fans can find the scene Bob references starting around time mark 1:12 in the film.

A review of the new Avion receiver and a few thoughts about DRM

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Many thanks to SWLing Post reader, Mike Barraclough, for sharing a link to this review of the new Avion DRM receiver by DRM Radio Forum user PhilipOneL. I’ve pasted his evaluation of the Avion below–you can read this, along with the full discussion thread, on the DRM Radio Forum:

I received my Avion AV-DR-1401 this afternoon and have had it up and running for a couple of hours. There is no instruction booklet with it so I am puzzling over the 41-button remote. It is not as user-friendly as I hoped.

First impression: somewhat cheap feel to it. I have put a small bend already in the thin but long aerial. But that is just the outside (handle, volume control, master power switch, and aerial); I hope it works well anyway. But that cheapness hurts when the price of the radio was fairly high to begin with and I paid more than I wanted for a private company to ship it (Fedex).

The radio arrived with its battery fully charged: nice. (But I need to get an adaptor for the AC adaptor’s mains plug which has tubular prongs rather than the North American blade prongs.) I like a lot the fact that it runs normally with its internal battery rather than plugged into mains. This means I can carry it away from noise sources. And it is very carryable — it reminds me of a small 1965-era beach radio in size.

Turned on, it scanned the local FM spectrum well and registered all the local stations. But I cannot get the Scan function to operate on MW and SW, nor in DRM mode. With an outside antenna (8 metre wire) attached, it was able to get the AIR DRM broadcast on 7550 kHz and decode it. It didn’t seem to be able to get enough signal with just the extending aerial.

I have not figured out yet how to make it register a medium-wave, shortwave, or DRM station in its memory; it does not happen when the button labelled “Delete / Store” is pushed. Among the 41 buttons, there is no other likely candidate for that function.

Shortwave sensitivity in AM mode seems to be poor. I was listening, for instance, to ERT Greece on 9420 on the three receivers now on my desk: Satellit 750, MorphyRichards 27024, and the Avion DR-1401, each in turn connected to the same outdoor antenna. The MR27024 produces the best sound and greatest s/n ratio. It seems far more sensitive than the Avion. But who knows? I may discover I am doing something wrong with the set.

Tuning can be done by inputting a frequency on the remote. Alternatively, the volume wheel can be pushed (this takes two hands) to convert it to a tuning knob. Two problems are apparent. One is that the signal is muted as you tune until you wait on a frequency for four or five seconds. Thus it is a slow and aggravating experience to try to tune across a band looking for signals. Secondly, as soon as a station is tuned and producing audio, the knob goes back to being a volume control. Grrrr. (I think there is a professor at all the design schools who seems to be telling all her/his students to be visually minimalist in design and to give every knob multiple functions. That professor should be publicly shamed until she/he recants and causes all the students to go back to multiple knobs each of which does one thing well.) When the radio gets itself ready to produce audio it seems to ramp itself up to full audio in a series of four steps, each a half-second or so after the last — it is an odd-sounding process. It is like a faulty AGC circuit; perhaps it is.

Sound quality is mediocre at best on AM (both mw and sw). I didn’t listen long enough to the DRM signal from AIR before it signed off to get a good idea of DRM audio quality; I was busy cooking supper. FM audio is mediocre too on the internal speakers but, piped out through the headphone jack to external speakers, it is quite good. When I piped the AM audio out it still seemed mediocre.

Why the AM sound is mediocre seems to be related to two things: the tiny speakers (about 8 cm or 3.3 inches) and the bandwidth at the radio stage. Even comparatively strong (and clean) signals like RHC on 6000 kHz have what may be adjacent signals mixing in — perhaps even internal mixing products? I heard a splash of a local FM station at one point while listening to a shortwave band.

I have written my contact at Avion (Ankit) asking for an instruction booklet, or a pdf of one. I hope I’ll get that early next week (if indeed they have one).

I hope over the next week I will get some chances to check out more DRM signals. I am also hoping that my gradual love affair with the MorphyRichards radio will be replicated here. When I first got the MR27024 I was very cranky about its weird ways of doing things. But once I got a good antenna on it, and got used to its ways, I prefer it to all my other radios as a table-top radio (that is, one useful for listening to specific regular stations). The MR’s radio-stage DSP is quite lovely and makes for good sound. I doubt the Avion will seduce me to quite the same extent, but it may grow on me in other ways.

I understand the problems with DRM but I am still a fan of of the system. I bought this Avion set partly in hopes that I would encourage the manufacturer in some small way. I will use it but I suspect that the minimalist design features (which were also a part of the MorphyRichards design) will turn off users of the Avion.

I’m not terribly surprised by this reviewer’s assessment. Just looking at some of the preliminary info on the Avion receiver last year made me think of previous DRM portables like the Newstar DR111 and the Uniwave Di-Wave 100.

The UniWave Di-Wave/Di-Wave 100.

The UniWave Di-Wave/Di-Wave 100.

I have a hunch all of these designs were fleshed out by engineers and entrepreneurs who had not gotten customer input in advance.

It’s sad, too. While I know DRM (via the shortwaves) was a “cart before the horse” innovation–meaning, broadcasters adopted the technology well before consumer receivers were on the market.

I really wish the medium would’ve gained traction.

While I prefer the rich sonic texture of amplitude modulation, I love listening to DRM broadcasts well. Last year, during my presentation at PARI, I played a recording of a piano concerto I heard on one of Radio New Zealand International’s DRM broadcasts. If memory serves, the audio clip was taken from this recording I made on June 21, 2104:

Through the presentation room’s hi-fi system, the music sounded absolutely brilliant.

To put what this audience was hearing in perspective, I told them:

“We’re listening to a radio station some 8,300 miles away without the use of the Internet, mobile phones, satellites, or any sort of subscription service. We’re hearing FM-quality audio, streamed wirelessly and originating from the other side of our planet.”

I then received a number of questions like: “How is this technology possible?” and “Do they make car radios that can receive these broadcasts?”

There’s magic in DRM. Sadly, I feel its deployment was awkward and its window of opportunity may have already passed. An affordable, effective, and simple DRM receiver (combined with serious, viral publicity) could turn the tide somewhat–but it doesn’t seem like this will happen anytime soon. Each new DRM portable is only a slightly improved iteration of its predecessor and the price tag continues to be too high for effective market penetration.

I want to be proven wrong, though.