Hal Kneller is a 40 year veteran of the broadcast industry working both as an engineer for WGCU, WGSM, WCTO, WPAT as well as owner/operator of five of his own stations.
Hal is a past International Sales Manager for Europe for Nautel. He also worked for iBiquity Digital Corporation as Director of International Broadcast Development where he played a pivotal role in the promotion of Digital Radio.
Read more Digital Radio Showcase
by Hal Kneller
Welcome to Digital Radio Showcase, a regular column featuring the latest technical news and information regarding in-band digital radio solutions including HD RadioTM technology and Digital Radio Mondiale (DRM).
The big story for this issue of Digital Showcase is HD PowerBoostTM is on the air at WAMU (FM) in Washington, D.C. NAB Convention attendees may recall several Nautel technical papers presented by software engineer Philipp Schmid. In short, HD PowerBoost is a technology that enhances the PAPR (Peak to Average Power Reduction) by combining the analog as well as the HD Radio carriers together and then performing peak reduction. In the normal iBiquity mode only the HD Radio carriers are peak-reduced.
HD PowerBoost has been under development at Nautel for over three years and was demonstrated in a working transmitter and formally introduced as a product at the Las Vegas NAB Convention in April 2010. Now HD PowerBoost is being tested on the air at WAMU and has also passed verification testing at NPR Labs in Washington, D.C. as the final measures prior to release to Nautel customers.
While HD PowerBoost primarily was developed to improve the output power of an FM amplifier (by up to 30%), and at the same time improve the operating efficiency, an additional benefit is the HD Radio sidebands can be regenerated at whatever power level is required, including asymmetrically, if so desired. In the case of WAMU, -14 dBc is operating on the lower sideband while -10 dBc is running on the upper sideband. Preliminary anecdotal reception reports are extremely positive from station personnel, and iBiquity reports a stronger and more consistent HD Radio signal at their headquarters in Columbia, MD about 40 miles distant.
On 25 September, mere days before the start of this year’s RADIO SHOW in Washington, WAMU took to the air with HD PowerBoost and -14/-10 dBc asymmetrical transmission. Richard Cassidy of WAMU reported the following day, “the increase in upper sideband power from -14 dBc to -10 dBc has resulted in marked improvement in HD coverage outside our 54 dBu contour. As I went into shadowed areas I was able to enjoy the Big Broadcast rebroadcast on HD-3 all the way back to Rockville. So I caught Dragnet and a good Gunsmoke episode without losing the signal at important places in the stories…very cool.”
Just prior to the opening of the RADIO SHOW, APRE (Association of Public Radio Engineers) held a one-day Public Radio Engineering Conference at NPR headquarters where lab results were discussed by John Kean who oversaw the verification testing as well as a report from John Holt, WAMU Chief Engineer. This was the first public unveiling that HD PowerBoost was on the air, and he reported that they were the first station to operate asymmetrical HD sidebands.
Read more on this story from RADIO WORLD who covered the conference.
It is anticipated that initial customer shipments of HD PowerBoost exciters will occur later this year. In order to utilize the system in existing NV Series transmitters which can be field-retrofitted, a new exciter card will be supplied. Future production will feature the new exciter card in all NV transmitters and HD PowerBoost will be enabled with a software key either at the factory or at a later date by the customer.
Last issue I said we would discuss operating modes for DRM, and we will, but first there was some exciting DRM news at the IBC in Amsterdam in September. An over-the-air transmission from UK to Amsterdam in Medium Wave of a DRM small-scale motion video was received on a standard consumer-style receiver. Developed by members of the DRM Consortium, the technology is known as Diveemo. This adds yet another rich-media function to DRM and DRM+. Diveemo can be used for education (distance learning) as well as for commercial purposes and it can operate over any of the DRM frequency ranges using data rates as low as 48 kb/s. As DRM is quite configurable, so is Diveemo’s bit rate to take advantage of additional quality where more bandwidth is available.
DRM has a great deal of flexibility when being configured for MW/LW and SW broadcasting in terms of bandwidth and data throughput, and in terms of throughput with DRM+ in the VHF bands. Why do we need this? Because different bands require different bandwidths. We might have 18 kHz available on a medium wave in one location and perhaps as little as 5 kHz in a shortwave band under certain circumstances. For medium wave, some regions use 10 kHz spacing while others use 9 kHz. So, configurability is important when dealing with a universal standard. Within the given bandwidth, we can trade off throughput for robustness which will, in turn affect coverage area. If our desired area has considerable signal strength and lack of interference, we can elect a mode with more bits-per-second, and conversely, if we’re struggling with a weak signal or interference … then robustness would be the safer choice.
Finally, different countries have different needs and preferences as they contemplate the move towards digitalization. While the US has selected HD RadioTM technology as its official digital standard, Canada remains undecided on where it goes in the future. Mexico may be leaning towards HD Radio transmissions and has authorized a number of stations in the US border region already, and there were test transmissions in several other cities as well. In the US, DRM (short wave) is being tested in Alaska as a way to cover the entire state with one signal. Elsewhere in the Americas, Panama and Dominican Republic have chosen HD Radio technology. Brazil has spent several years trying to decide what technology to choose between DRM and HD Radio systems, and more recently seems to be undecided. Perhaps after the new presidential administration has time to study the matter, a final decision will be made. Brazil is considered a barometer in South America; other countries are watching what happens.
Outside the Americas, in Asia, the Philippines officially adopted the FM system of HD Radio broadcasting and China is taking a very close look at it but has also experimented with DRM and DAB, along with their own solution for mobile called CMMB. India has adopted DRM as its official digital radio system, and other countries in the region are also weighing options. DAB or DAB+ from the Eureka family is also being tested or adopted in some Asian countries. South Korea, for example, is studying all the possible digital systems to determine what might be the most appropriate for their country.
In Europe, many countries are planning DAB+ rollouts; however, private broadcasters often prefer either HD Radio broadcasting or DRM as an option to the DAB system. So we may see some countries with a multi-system approach with the future to be more market driven. The DRM system is designed to hand back and forth between DAB/DAB+ so there is some inert compatibility to having a multi-standard, and Switzerland is heading down that path with HD Radio and DAB+. Romania and Ukraine have HD signals operating. To the east of Europe, Russia has also announced that it has formally adopted the DRM standard.
Adoption and actual broadcast may not necessarily be equal. For instance, we see both DRM and HD Radio broadcasts in a number of countries where there is no official governmental standardization. And at the same time, we see some limited broadcasts in other countries where there is official adoption but not yet a full national rollout of the particular technology selected. No one system appears right for everyone.