Doug Lung / 04.15.2011 12:00AM
Manufacturers Highlight Mobile DTV at 2011 NAB Show
It was no surprise that transmitter manufacturers focused on Mobile DTV at this year's NAB. TV broadcast engineers now have a wide range of mobile exciters, multiplexers and encoding systems to choose from. Even better news is that while all manufacturers offer their own complete mobile DTV solution (exciter, multiplexer, encoder) and prefer you use their products, some of the exciters will work with a range of Mobile DTV multiplexers. Axcera was one of the companies claiming its exciter would work with streams from both the Rohde and Schwarz and Harris multiplexers. Larcan showed its first ATSC mobile DTV exciter/multiplexer/encoder solution while others, such as Harris, showed major upgrades to their first generation mobile DTV gear.
While not directly related to Mobile DTV, several new and updated digital on-channel repeaters (DOCRs) and single frequency network compatible exciters/transmitters were on display. Broadcasters are likely to need to use one of these technologies to improve reception on mobile/handheld devices inside buildings or in areas obstructed by terrain. Some of the new DOCRs, like those from Linear and Screen Services, claim the ability to work even if the output signal at the input to the repeater is 30 dB or more above the received signal to be repeated. This should simplify installation and allow greater output powers. Lower power transmitters in a single frequency network and digital on-channel repeaters need mask filters to protect adjacent channels. I was pleased to see Dielectric (SPX), RFS and others offering low power, compact filters that were able to meet the full power emission mask.
I did not see as many new products in the antenna/transmission line category as in previous years. One new product that stood out was ERI's 1329Line rigid transmission line, which combines the copper inner conductor from ERI's MACXLine with an aluminum outer conductor. ERI said power handling and loss for the hybrid line is comparable to that of all copper line, at a much lower cost and lighter weight.
I'll have more details on these and other products in my June RF Technology column in TV Technology magazine.