AM Power Savings AM Power Savings Using IBOC and MDCL Using IBOC and MDCL together g Optional Title
Presentation Overview • Common types of MDCL – Amplitude Modulation Companding (AMC) A lit d M d l ti C di (AMC) – Dynamic Amplitude Modulation (DAM) • Implementation on NX (and older products) • Implementation on NX (and older products) • What are the implications? – Typical power reduction Typical power reduction – Spectral mask concerns – Will your listeners notice? Will your listeners notice? • Recommendations and conclusions Optional Title
Amplitude Modulation Companding (AMC) • Reduces overall gain on envelope signal at high mod • Relatively inaudible to the listener • Tends to maintain T d t i t i high SNR on received signal received signal Optional Title
Dynamic Amplitude Modulation (DAM) • Reduces carrier only at low mod – sidebands are unchanged h d • Boosts received audio at low mod audio at low mod • Can result in higher savings if less savings if less processed audio is used Optional Title
NX MDCL Implementation • MDCL techniques are implemented digitally in the NX exciter – Precise peak control – Allows adjustable compression and different curves • The MDCL-modified signal from the NX exciter is used to replace the carrier from the Exgine used to replace the carrier from the Exgine – Any technique can be used without requiring Ibiquity software support software support – Added benefit of removing the reliance of the analog AM on the IBOC equipment Optional Title
What does adding HD do to the AM? • Envelope bandwidth is increased • To an AM receiver, looks like additional noise additional noise • Effect is worse with DAM with DAM Optional Title
Typical power reductions MDCL Carrier Mod IBOC Total Savings AM AM 50 50 2.62 2 62 2 84 2.84 55.46 55 46 0% 0% AMC 32.81 1.72 2.84 36.39 34.4% B Basic i 30 18 30.18 2 62 2.62 2.84 2 84 3 35.64 64 3 35.7% % DAM F ll Full 40 04 40.04 2.62 2 62 2 84 2.84 45.50 45 50 18.0% 18 0% DAM • Savings of 20-30% can be realized Optional Title
Spectral mask compliance • Decreasing the carrier is effectively the same as elevating the carriers to the transmitter • This effect is worse for DAM – AMC decreases the gain on the envelope signal during peaks and troughs – DAM decreases the carrier when at lower mod DAM decreases the carrier when at lower mod depths, effectively increasing mod depth – The majority of spectral regrowth energy occurs due j y p g gy to distortion in the troughs Optional Title
Audio quality measurements: enhanced carriers on • Standard AM is the best, as expected, but AMC is close • SNR is worst at high and low mod depths • DAM emphasizes DAM h i peaks and troughs, resulting in more resulting in more audible artifacts Optional Title
Audio quality measurements: enhanced carriers off • Boosts the received SNR by 4-5 dB • Makes up for the lost SNR from MDCL • Reduces audible R d dibl impact of IBOC Optional Title
Conclusions • AMC offers the most benefit when used with IBOC • If turning on MDCL: If t i MDCL – Spectral compliance must be rechecked – Audio quality should be reevaluated Audio quality should be reevaluated – If possible, enhanced carriers should be disabled • Significant power savings of 20-30% are possible • Significant power savings of 20 30% are possible NX Series MW NX Series MW 25kW – 2.0MW NX50 NX100 NX400 NX25 NX200 NX300 Optional Title
Thank You Thank You Optional Title
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