Audio System - HD Radio(TM) Overview
91 12 18
August 13, 2012
2030437
Vehicle Information
Condition
HD Radio Overview
This Technical Bulletin provides an overview of HD Radio technology and terminology. The following questions are addressed.
1. What is HD Radio?
2. What is HD Radio "Multicasting" (HD2, HD3, etc.)?
3. What is the technology behind the Digital HD Radio Signal?
4. Can HD Radio be switched OFF?
5. What is "Blending"?
6. What is audio level "Alignment" and "Misalignment"?
7. What can affect HD Radio reception
Technical Background
The HD Radio technology was developed by iBiquity Digital Corporation. They are the HD radio patent holders, and as a result, they are responsible for providing licenses to local radio stations nationwide allowing them to broadcast with the HD Radio technology.
1. What is HD Radio?
HD Radio is a digital rebroadcast of the same analog signal content coming from the source radio station. This applies to "HD 1" channels only. HD Radio signals can be found on both AM and FM bands.
^ AM stations broadcasting with HD Radio Technology will have the same or similar sound quality as an analog FM broadcast.
^ FM stations broadcasting in HD Radio Technology will have the same or similar sound quality as a retail purchased CD.
2. What is HD Radio "Multicasting" (HD2, HD3, etc.)?
Multicasting is when a radio station provides a digital only sub-station on HD2, HD3, etc. (figure 1).
^ There is no duplicate analog station for these multicasted stations.
^ FM station providers are able to offer this additional content because the digital conversion of the normal analog signal opens up a larger amount of available bandwidth.
3. What is the technology behind the Digital HD Radio Signal?
^ A digital HD Radio signal is transmitted along with the analog signal, but is broadcasted at reduced signal strength. The two signals are essentially overlaid with each other and sent simultaneously.
^ A digital HD Radio signal area of coverage is approximately 90% of the area of coverage for the analog signal. Keep in mind this area of coverage can be affected by the environmental conditions and it is not a uniform area of coverage.
^ Additionally, because HD signal generators require an additional step prior to transmitting the radio signal, an HD station can have a 2-3 second delay when compared to the same stations analog signal. Because Volkswagen radios will automatically switch between HD and analog signals depending on signal strength, this can cause an "echoing" effect over the vehicles speakers (See section 5).
4. Can HD Radio be switched OFF?
^ The user can control whether or not the HD Radio stations are shown on the radio display by switching the feature ON or OFF in the "Setup" menu of the radio.
^ In areas where HD signal strength is weak or unreliable, this setting will allow the customer to experience more consistent radio operation.
5. What is "Blending"?
Blending is the switching back and forth between the analog and HD Radio digital signals. This is considered a normal condition. Blending will occur more frequently when traveling in and around the fringe area of reception for the digital signal.
^ Blending only 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 can lead to customer complaints (See section 6)
^ Change in volume levels
^ Echo effect
^ Blending only occurs on the main HD1 station.
^ Blending does not occur on the multicasted sub-stations of HD2, HD3, etc. because there is no analog backup for this programming. Instead, the audio will mute when traveling outside the area of signal coverage. This may result in the HD Radio icon on the radio screen switching ON and OFF - this is considered a normal function of the HD Radio.
6. What is audio level "Alignment" and "Misalignment"?
Audio level Alignment is the syncing of the digital HD Radio signal and analog signal and it is designed to smooth out the process of blending.
^ Misalignment occurs when the digital and analog signals are out of sync.
^ Echoing can occur during misalignment. The customer may notice a time delay between the two signals.
^ The volume level can change up or down when misalignment occurs. This also occurs during the "Blending" process. The radio station broadcasting the signal is ultimately responsible for the alignment of the digital HD Radio signal and the analog signal audio levels.
^ Complaints caused by misalignment are not a vehicle issue and replacing parts will not resolve the concern. Report any of the above conditions to the respective local radio station.
7. What can affect HD Radio reception?
The reception of a digital HD Radio can be interrupted by traveling near high terrain, high buildings, bridges,
tunnels, etc.
Production Solution
Not applicable.
Service
^ For assistance diagnosing HD radio concerns please contact the Volkswagen Technical Helpline.
^ 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
Information only.
Required Parts and Tools
No Special Parts required.
No Special Tools required
Additional Information
All part and service references provided in this Technical Bulletin are subject to change and/or removal.
Always check with your Parts Dept. and Repair Manuals for the latest information.