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Radio Marti Begins Shortwave DRM Transmissions

USAGM aims to help drive development of low-cost DRM receivers

Radio Marti began Digital Radio Mondiale (DRM) shortwave transmissions on Feb. 4. Part of the U.S. Agency for Global Media (USAGM), Radio Marti broadcasts news and other programs to Cuba. The DRM shortwave transmissions are from USAGM’s Greenville, North Carolina, site.

Gary Koster, USAGM’s broadcast radio technician, Gerhard Straub, USAGM director of broadcast technologies division, and Macon Dail, USAGM chief engineer at Greenville stand in front of the transmitter and other equipment being used for the DRM transmissions.

USAGM has transmitted in DRM before. There were some transmissions from Briech, Morocco, in the early 2000s. Greenville tested DRM in 2009 in partnership with what was then known as HCJB Global Technology. So why are they back now after an absence of over a decade?

“We want to experiment a bit with different modes and services available on DRM. We also want to help push the development of low-cost receivers and the best way to do that is to put some transmissions on the air, explains Gerhard Straub, director of USAGM’s Broadcast Technologies Division.

An RFMondiale reference receiver is shown with a Transradio DM0D3 DRM exciter and a RFMondiale LiveWire audio router. The large screen is the user interface for a 1RU content server situated behind the screen.

Greenville is using a Continental 617-A transmitter, along with a Transradio DMOD3 DRM modulator and RF Mondiale RFMondial content server. The antenna is a rhombic aimed at 174 degrees. The average power on DRM is 5,000 W. The schedule is daily from 1700–0200 UTC on 7345 kHz.

The Radio Marti broadcasts are in xHE-ACC, the latest and standard DRM codec. “We need the lower bitrates because we are running pretty low power and we are trying to keep the signal robust,” explains Straub.

Although these are regular transmissions, USAGM is making adjustments along the way. The first few days tests consisted of two audio streams, with Voice of America in English in addition to Radio Marti. Now Radio Marti is the sole audio service. The transmissions are using the text box and there are plans to transmit images (MOT Slideshow) and Journaline, an RSS type feed.

For the time being, Greenville will be the only USAGM site broadcasting in DRM.

As for Greenville, “There is no definitive time period for the transmissions. We will continue the transmissions until we need to devote resources to other projects or feel we have achieved what we needed,” said Straub.

Hans Johnson has worked in the shortwave broadcasting industry for over 20 years in consulting, frequency management and sales.