Saturday, June 17, 2017

VOA Radiogram Is Dead, Long Live Shortwave Radiogram

Kim Andrew Elliott is retiring, and that means no more VOA Radiogram.  The last one airs this weekend. However, Kim will continue this innovative effort on a new transmitter, WRMI in Miami. The new program is called Shortwave Radiogram, and the format is just like the old one.

The time/frequency schedule changes considerably, and next weekend will be something of a new set of variables in this summer's iffy HF propagation.  I assume that Kim will need a lot of reports.  Here are the new addresses:

Email address

And here is the new schedule:

WRMI Florida
Asia-Pacific, Europe
WRMI Florida
Americas, Asia-Pacific
WRMI Florida
Europe, Asia-Pacific

* WRMI transmissions will continue as Shortwave Radiogram beginning June 25.

Some might wonder why a utility column spends so much time on a broadcast program.  The reason is that we are radio amateurs, and one of our major functions is to innovate communications technology.  VOA Radiogram, at its start 4 years ago, was a major innovation. It has pioneered techniques by which HF broadcasting can begin to adapt itself to a digital age, without having to replace all the equipment on both the transmit and receive sides.

At first, many people thought the whole idea was daft.  How does one send digital modes designed for amateur SSB transceivers over analog HF transmitters in double-sideband AM?  It's somewhat against common sense, but remember that these modes are essentially audio.  They're generated as audio, and the amateur transceiver turns them into SSB.  The receiver then turns them back into audio for decode by external equipment.  The transmitter and receiver in the middle can be AM.  Same flow.

The major technical challenges dealt with the nature of HF broadcast audio, which is heavily processed and compressed.  There were various issues with levels, hum in the old transmitters, audio harmonics, and duty cycles.  MFSK, with its 100% duty cycle, became, somewhat counter-intuitively, the best-received mode.  Olivia works too, but at its slowest speeds and largest bandwidths.

Later on, the receiving software was given a real workout. The show had more or less standardized on fldigi, a ham program, and the partnership led to the technical evolution of both. It became clear that digital modes on analog HF transmitters could increase their coverage. The concept also suggested means of penetrating jamming, and even sending text, however slowly, to countries where the Internet had been blocked by censors.  Many foreign languages with non-Latin alphabets were tried, and they all worked. MFSK images, which work a bit like SSTV, were also given a good test. They're noisy with typically lousy band conditions, but they're good enough .  Now they are a staple.

More recently, we have seen adaptations of fldigi for receiving by the technically untrained. This is obviously important if HF broadcasting is to evolve. First, a version of flmsg for Android phones was issued, and then another adaptation (TIVAR) made copying on smartphones a breeze.  I've done it here.  You set the phone near a speaker, start the program, and away you go.

Let's give Kim a Bravo Zulu on his retirement, and work with him to continue advancing the state of world communication.