Wheatstone Baseband192 Completes All-digital Air Chain for BE FM Exciter

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Wheatstone Baseband192 Completes All-digital Air Chain for BE FM Exciter

Aug 7, 2013 2:22 PM

Since this news was announced, Wheatstone has subsequently tested Baseband192 with other exciter manufacturers. Read the update here:
Wheatstone Baseband192 Completes All-digital Air Chain

New Bern, NC - Aug 7, 2013 - On the heels the news of KTWN-FM's initial broadcast from an all-digital air chain using Wheatstone Baseband192, Wheatstone has completed the connectivity of its digital "last mile" interface into the Broadcast Electronics (BE) STXe60 FM exciter.

Testing was completed at BE's factory in Quincy, IL, on Aug. 2, representing a 100 percent digital air chain. "We are pleased to see so much support from major manufacturers," said Jeff Keith, Wheatstone senior product design engineer. The test involved a Wheatstone VP-8IP audio processor with Baseband192 coupled to a BE STXe60 exciter.

The digital interface is available as a standard feature in Wheatstone AirAura X3, FM-531HD and VP-8IP audio processors to produce an AES3 output into FM exciters now equipped with a digital baseband input.

Wheatstone Baseband192 was built into the Wheatstone processors four years ago but had been held back until FM transmitter manufacturers could offer a digital multiplex interface to their transmitters. Following announcements at the recent NAB 2013 convention, FM exciters became available that could accept the necessary digital multiplex signal.

With Baseband192 directly connected into the baseband input of their FM exciters, broadcasters are able to complete the "last mile" of the 100 percent digital FM air chain, from the audio playout system to the transmitter's digital FM modulator.

Previously, broadcasters had two options for interfacing the audio processing to the exciter: analog composite or digital AES/EBU (AES3). The first required D/A and A/D conversion and resulted in unpleasant audio artifacts typical of this method. The other, although digital, didn't offer a composite interface and therefore came at a loudness penalty due to the loss of any downstream benefits generated by the FM processor's composite clipping.

Wheatstone's new, third interface option for its audio processors doesn't require A/D/A conversion or come with a loudness penalty. Because the baseband192 signal encompasses the entire multiplex spectrum after stereo generation, it includes any loudness increases that may have been contributed by the FM processor's composite clipper. A single AES3 cable between the Wheatstone processor and the transmitter carries the baseband signal, bypassing the need for multiplexing in the exciter and eliminating the resulting signal overshoot and associated loudness tradeoff.

Baseband192 is a 192kHz sample rate, pure digital interface. The Baseband192 signal represents the FM processor's entire stereo multiplex spectrum - including most subcarriers. The stereo multiplex signal remains in the digital domain after stereo generation so there are no D/A conversions, no sample rate conversions, and no imperfect analog circuitry standing in the way of a perfect handoff of the stereo baseband signal to the FM exciter.

Baseband192 is being offered to broadcasters as a standard feature on new orders and as a free software download for existing AirAura X3, FM-531HD and VP-8IP audio processors.

BE's baseband capability will be available in any second generation BE STX product - including the full line of STX LP transmitters and the STXe60 and STXe500 products. BE's STXe60, a Radio magazine Pick Hit winner at the 2013 NAB Show, is a complete redesign of the exciter portion of BE's STX product line. This design includes full digital direct-to-carrier modulation and now, with Baseband192 compatibility, is able to offer a 100 percent digital chain. This exciter is standard on all transmitters currently shipping at BE.

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