Audio - HD Radio Overview
91 HD Radio Overview91 11 17
2026611/3
October 5, 2011.
Supersedes Technical Service Bulletin Group 91 number 11 - 91 dated July 11, 2011 for reasons listed below.
Affected Vehicles
Condition
This Technical Bulletin provides an overview for HD Radio.
Technical Background
iBiquity Digital Corporation is the company that owns the technology and patents for HD Radio, as well as providing licenses to local radio stations allowing them to broadcast with HD Radio Technology. HD Radio is a digital rebroadcast of the analog signal station content and exists on both AM and FM bands. AM stations that broadcast with HD Radio Technology will have the same or similar quality sound as that of FM sound quality. FM stations that broadcast in HD Radio Technology will have the same or similar quality sound as that of CD sound quality.
The digital conversion of the analog signal results in a larger bandwidth available to FM station providers. This allows providers to offer additional content (H D2, HD3, and HD4). The process is called multicasting.
HD Radio digital signal:
^ Is transmitted along the analog signal and is broadcast at reduced signal strengths.
^ HD Radio digital signal coverage area is approximately 90% of the analog signal coverage area.
^ Can be turned on and off in the Settings, or Setup menu. Refer to TSB 2026657 for additional information.
^ When out of HD Radio digital signal coverage area, HD1 will revert back to an analog signal. HD2, HD3, and HD4 multicast channels will mute as there are no analog backup for this programming.
Blending:
^ Blending is the switching back and forth between analog and HD Radio digital signals, and is a normal condition. This is especially true on the fringe area of reception.
^ Blending takes place when the vehicle travels in and out of the HD Radio digital signal coverage area.
^ Blending produces a change in sound, tone, and quality which may lead to customer complaints.
Audio level alignment:
^ Alignment is the synching of the HD Radio digital and analog signals, and provides smooth blending.
^ Effects of misalignment:
^ Echoing is a condition where the sound seems out of sync or there's a time delay.
^ Volume level changing up or down when in HD Radio mode, not blending between analog and digital signals.
^ Radio stations are responsible for the alignment of the HD Radio digital and analog signal audio level. Complaints caused by misalignment are not a vehicle issue and replacing parts will not resolve the concern. Report any of the above alignment conditions to the respective radio station.
Other HD Radio digital signal reception issues:
^ HD Radio digital signal reception may be interrupted by terrain, buildings, bridges, tunnels, etc.
Production Solution
Not applicable.
Service
Please see attached troubleshooting guide to aid in diagnosis.
Please contact the Technical Assistance Center if the troubleshooting guide does not help resolve issues with HD Radio.
To learn more about HD Radio please visit http://www.hdradio.com/
To hear samples of an AM/FM analog and digital signal please visit http://www.hdradio.com/what-is-hd-radio and select How does it sound".
Report station issues at: http://www. ibiquity.com/automotive/report_radio_station_experiences
Warranty
This TSB is informational only and not applicable to any Audi warranty.
Additional Information
Please see TSB 2026657, HD Radio presets.
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service manuals for the latest information.
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