No, your presenter is not “drinking the iBiquity Kool-Aid” IBOC / HD Radio TM : Engineering Concerns Aaron Read (G.M. : Public Radio for the Finger Lakes) Already decided HD Radio TM is right for you? Here’s a look at what you’ll need to do.

See also : and Essential Questions This session is not about whether or not your operation can deal with the various issues involved with HD Radio. We’re here to look at what’s involved with the engineering behind installing HD Radio at your facility or facilities.

See also : and Are you an AM station? If you don’t have an FM station, be advised: we’re not going to talk much about AM IBOC.  It has a lot of problems and the entire future of AM IBOC is arguably still in question.  Digital sidebands cause significant 1 st adjacent interference – nighttime skywave means that interference goes 1000’s of miles.  Audio quality improvements are impressive for music but sounds pretty “crunchy” for news/talk.

See also : and What is HD Radio? Hint: the “HD” doesn’t stand for anything! These sidebands do put some more RF energy on the adjacent channels, so IBOC can cause 1 st -adjacent interference issues. Backwards-compatible, existing analog radios ignore the digital (sounds like “white noise”) HD Radio is a brand name by the creator: iBiquity  Technical term is IBOC : In-Band/On-Channel. Uses digital sidebands on your existing analog signal.

See also : and Is HD Radio required? No – it is currently a hybrid system: both analog and digital. Fully backwards-compatible, and (by FCC R&O) optional for stations to migrate.  All-digital system is possible, but FCC not allowing it.  All-digital does hold promise for more data b/w and less interference issues. Note that eventually it’s likely the marketplace / listeners will demand you migrate to HD.

See also : and What is HD Radio? Also known as “IBOC” IBOC-equipped radio will first play the analog audio feed immediately, then begin buffering the audio data.  This results in approx. 7 second delay of program audio. After a few seconds, the radio will “blend” to the digital audio feed.  Make sure your analog & digital audio feeds are time-synched!  Digital audio uses the HDC codec. Details are proprietary, but rumored to be a variant of the impressive AAC codec. If the HD signal is lost, the radio blends back to analog.

See also : and Simple FM IBOC Transmission Topology – All IBOC Gear at Transmitter Site diagram courtesy of The IBOC Handbook, page 401

See also : and FM IBOC Transmission Topology – with Exporter and Exgine Modules diagram courtesy of The IBOC Handbook, page 405

See also : and FM IBOC Transmission Topology – with Exporter & Exgine Modules, plus Importer diagram courtesy of The IBOC Handbook, page 413

See also : and What is HD Radio? (FM) Also known as “IBOC” The digital carriers merely transmit data: ones and zeros. 96kbps in standard mode  96kbps + 12 or 24kbps in extended hybrid modes  Ext.Hybrid puts more digital carriers closer to the analog signal – more risk for self-interference. That digital payload can be divided in many ways, and not just for audio.

See also : and What is HD Radio? (AM) Also known as “IBOC” Also just transmits bits, but less bandwidth – about 32kbps total.  Multicasting is not available yet.  Does have enough data (barely) for PAD.  Chief advantage is in improved audio quality.  Is authorized for operation at night and on directional arrays.

See also : and What benefits does IBOC have? Robustness = no static, no fades, no multipath Quality = increases audio b/w from 15 to 20kHz (i.e. more high end) for FM.  Note, “quality” does not mean “fidelity” – it’s still a lossy codec…but on FM it’s impressive.  On AM, it’s more complicated, but generally better. Flexibility = transmits DATA not AUDIO. You can, in theory, use those bits for lots of things.  PAD, iTunes tagging, MP3 downloads, on-demand text/audio/video.

See also : and FM IBOC’s Killer App Multicasting = Extra Radio Stations on 1 Signal HD1 must always be a simulcast of your analog signal. Multicasting changes 96kbps for HD signal into subdivisions:  48kbps each : HD1 & HD2  32kbps each : HD1 & HD2 & HD3  48kbps : HD1 + 24kbps each : HD2 & HD3 Extended hybrid’s bits cannot be added to the 96kbps, but can be used alone for a single multicast channel.  48kbps each : HD1 & HD2 + 24kbps : HD3 Theoretical max up to HD7, practical limit is HD3  Less kbps = less audio quality  HD4 is possible but problematic in many ways.

See also : and FM IBOC’s Killer App??? iTunes Tagging Equipped radios have a “tag” button.  Press when you hear a song you like.  Radio saves tag info to your iPod.  When iPod is connected to iTunes, it goes to iTunes music store and buys the song for you. Very cool – but limited receivers, limited number of stations doing it. Requires massive investment in audio content mgmt & promotions.

See also : and FM IBOC Limitations The -10 vs -20dB Debate : NPR Labs Study IBOC injection is -20dB or 1/100 th of analog ERP (1000w analog = 10w digital) Coverage is considered inferior to analog Proposals to increase IBOC inj. to -10dB of 1/10 th of analog ERP.  Risk of severe adjacent channel interference. Avg. 26% loss of analog coverage / 41% of stations receive interference to one-third of service population.  …but portable HD may not work without it.

See also : and FM IBOC Limitations The -10 vs -20dB Debate : NPR Labs Study Summer 2008 – NPR Labs released first comprehensive, accurate IBOC coverage prediction model. At current -20dB IBOC ERP levels…  Mobile coverage = equivalent of analog  Indoor coverage = 50% of analog At -10dB IBOC ERP levels…  Mobile coverage = +18% over analog  Indoor coverage = 88% of analog

See also : and FM IBOC Limitations The -10 vs -20dB Debate : NPR Labs Study Hi-Level Combined Xmitter Systems will require SIGNIFICANT extra capacity.  Current HD xmitters de-rated by up to 50% Take a 20kW analog ERP station… -20dB : ~23kW analog + ~2kW digital -10dB : ~23kW analog + ~21kW digital …and ~21kW going into the reject load!!! Different for split-level combined, combined, or separate systems – but you get the idea: it’s not just a case of adding more watts.

See also : and FM IBOC Challenges IBOC requires time-delay of analog to match the digital – this can complicate your off-air monitoring scheme.  Normal silence sensors may not work effectively. Adding HD2 and HD3 is essentially like buying two new stations. It introduces significant challenges in programming, operations control, monitoring, etc. Do you have trouble filling ONE station with programming 24/7? Imagine adding two more! Or two more studios! Managing listener expectations – when the HD signal is lost, it just disappears immediately. That means HDn channels just mute (instead of fading out to static).

See also : and FM Translators and Boosters Boosters (Single Freq. Network)  NRSC-5 specs carrier synch, but no radios support it yet. Right now it’s only in prelim testing.  Relates to the -20 vs -10dB IBOC injection debate. Translators require* a separate exporter license from iBiquity = big bucks for a small signal.  * unless you get a heterodyning xlator, which are still vaporware and are pricey ($10-$20k)

See also : and FMeXtra? Digital SCA (Subcarrier) service Compatible with hybrid IBOC, but not all- digital IBOC. Transmits 64 – 156kbps  Stereo, RDS, analog SCA = less kbps avail. Transmits DATA, but architecture only supports audio via AAC at the moment.

See also : and FMeXtra Not meant as a multicast service, but can be used that way.  Really meant to supplant existing analog SCA Only one model of radio currently available: tabletop “Aruba”. FM only. Can function as a handy backup STL / TSL system (yourself or rent to others)  AAC codec = quality low kbps

See also : and Shameless Self-Promotion The IBOC Handbook : Understanding HD Radio TM Technology Looking to really learn the engineering of IBOC / HD Radio? Read this book!  First & Only Overview of the Newly-Approved NRSC-5 (IBOC) Standard.  Authored by David Maxson  Illustrated by Aaron Read Available on Amazon.com

See also : and Final Thoughts Questions – and please no:  Rants, Screeds, Diatribes, Harangues, Raving, Tirades, Bullyragging, Vociferation, Bloviating, Railing, Objurgating, Badgering, Molestation, Nettling, Ruffling, Badgering, Pestering, Heckling or Persecution. Tell us your situation, we’ll opine if HD Radio or FMeXtra is right for you! Aaron Read can be reached via Need an engineer?