IBOC HD RadioTM : Engineering Concerns Aaron Read G.M. : Public Radio for the Finger Lakes

1
IBOC / HD RadioTM Engineering ConcernsAaron
Read (G.M. Public Radio for the Finger Lakes)

• Already decided HD RadioTM is right for you?
  Heres a look at what youll need to do.

2
Essential Questions

• This session is not about whether or not your
  operation can deal with the various issues
  involved with HD Radio.
• Were here to look at whats involved with the
  engineering behind installing HD Radio at your
  facility or facilities.

3
Are you an AM station?

• If you dont have an FM station, be advised
  were 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 1st adjacent
  interference nighttime skywave means that
  interference goes 1000s of miles.
• Audio quality improvements are impressive for
  music but sounds pretty crunchy for news/talk.

4
What is HD Radio?Hint the HD doesnt stand
for anything!

• 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.

• These sidebands do put some more RF energy on the
  adjacent channels, so IBOC can cause 1st-adjacent
  interference issues.
• Backwards-compatible, existing analog radios
  ignore the digital (sounds like white noise)

5
Is HD Radio required?

• No it is currently a hybrid system both analog
  and digital. Fully backwards-compatible, and (by
  FCC RO) 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 its likely the marketplace
  / listeners will demand you migrate to HD.

6
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.

7
Simple FM IBOC Transmission Topology All IBOC
Gear at Transmitter Sitediagram courtesy of The
IBOC Handbook, page 401
8
FM IBOC Transmission Topology with Exporter and
Exgine Modulesdiagram courtesy of The IBOC
Handbook, page 405
9
FM IBOC Transmission Topology with Exporter
Exgine Modules, plus Importerdiagram courtesy of
The IBOC Handbook, page 413
10
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.

11
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.

12
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 its
  still a lossy codecbut on FM its impressive.
• On AM, its 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.

13
FM IBOCs Killer AppMulticasting 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 hybrids 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.

14
FM IBOCs Killer App???iTunes Tagging

• www.hdradio.com/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.

15
FM IBOC LimitationsThe -10 vs -20dB Debate NPR
Labs Study

• IBOC injection is -20dB or 1/100th of analog ERP
  (1000w analog 10w digital)
• Coverage is considered inferior to analog
• Proposals to increase IBOC inj. to -10dB of
  1/10th 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.

16
FM IBOC LimitationsThe -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

17
FM IBOC LimitationsThe -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
• _at_ -20dB 23kW analog 2kW digital
• _at_ -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 its not
  just a case of adding more watts.

18
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).

19
FM Translators and Boosters

• Boosters (Single Freq. Network)
• NRSC-5 specs carrier synch, but no radios support
  it yet. Right now its 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)

20
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.

21
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 audio _at_ low kbps

22
Shameless Self-PromotionThe IBOC Handbook
Understanding HD RadioTM 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

23
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, well opine if
• HD Radio or FMeXtra is right for you!
• Aaron Read can be reached via www.friedbagels.com/
  blog
• Need an engineer? www.sbe.org