# TB: Radio, Premium Sound System (Panasonic) Sound Inconsistent - Includes TB 91-06-06



## PanEuropean (Nov 3, 2001)

This is a fascinating and very well written TB that elaborates the reasons behind occasional variations in volume and radio reception that may be noticed when listening to modern car radios. In the Eos, this may manifest as a reduction in both volume and bass at certain times.
Here's an excerpt from the TB:
*Technical Background *
*1.* Due to environmental factors such as weak signal, or multipath condition, static can be heard on the radio. To counteract the static and to improve the customer’s reception quality, a Hicut filter has been introduced. 
*2.* Multipath is the reflection of the FM signal caused by a nearby building or other large natural object such as a hill or mountain. The reflection of the signal causes constructive and destructive interference causing static to be heard. 
*3.* Hills and mountains can also cause a loss of field strength. As FM is a line of sight technology, any object that gets between the antenna and the broadcasting tower can cause some loss of signal. 
*4.* Weak or poor stations will also cause the Hicut to occur in areas where the signal is very week. 
*5.* Lower level radio software causing inconsistent sound. The FM Hicut filter decreases static heard during short term reception loss and will mute the treble. This action gives the perception of volume loss, reduction in volume, and/or loss of sound quality on FM stations. This function is a normal part of the Panasonic Premium radio. DO NOT replace the radio for this condition. This is caused by a weak signal or other reception issues. 
*Production Solution *
Panasonic Premium Sound System Software level (0021) update to reduce/remove the current level of the FM Hicut in Panasonic radios.
*Service *
Antenna diagnosis must be made to ensure that vehicle does not encounter any other reception issues. Please follow these steps _(contained in the TB)_ to verify Antenna performance. 
*Tip:* Window tint may play a large role in the reduction of antenna performance.
I have attached the TB below. It is not a required update, in other words, if you are not encountering any of the problems described in the TB, you don't need to have it carried out on your car. If you are encountering the problems described, then the technician at your VW dealership will check your antenna to make sure there are no problems with the antenna (note the remark about window tint being a possible problem!), and if no antenna problems are found, the software in the radio will be flash-updated so that the 'Hicut filter' is less aggressive in its action.
If you have not already done so, please read the Eos forum post entitled Eos Technical Bulletins (TB) - Philosophy, How to Use, Index. This is *essential reading *for all VW owners who are curious enough to be reading TBs - it explains the philosophy and etiquette involved in TBs.
Michael


_Modified by PanEuropean at 3:36 PM 11-8-2006_


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## PanEuropean (Nov 3, 2001)

*Re: TB: Radio, Premium Sound System (Panasonic) Sound Inconsistent ... (PanEuropean)*

On November 6, TB 91-06-06 was revised and additional information was added to assist the technician in diagnosing proper function of the radio antennas.
TB 91-06-10 (attached below) supercedes and replaces 91-06-06.
Michael


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## Shaka (May 20, 2001)

*Re: TB: Radio, Premium Sound System (Panasonic) Sound Inconsistent ... (PanEuropean)*


_Quote, originally posted by *PanEuropean* »_*Tip:* Window tint may play a large role in the reduction of antenna performance.

Didn't we determine all the antenna are in the plastic trunk lid, and hence window tint should play no role?!


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## PanEuropean (Nov 3, 2001)

*Re: TB: Radio, Premium Sound System (Shaka)*

From what has been presented so far here on the forum, it appears that the antennas are in the trunk lid, but it is always possible that there may be changes from market to market. For example, all the European Phaetons have every antenna in the rear window glass, but the North American ones have additional antennas (GPS and analog cell phone) on the roof.
I have seen that phrase _("Window tint may play a large role in the reduction of antenna performance")_ in other technical publications that deal with antenna troubleshooting, so it is possible that it might have been carried over by error into the Eos procedure. I do know that there is a lot of truth to that warning - several Phaeton owners have totally destroyed antenna function by putting metallic film window tint on the inside of the back window.
The main point I think we need to consider is that at least VW of A is trying very, very hard to get troubleshooting information and software fixes out to the field as fast as possible, and in this context, we ought to give them credit (moral support) for that. 
I'm going to Switzerland tomorrow, so I won't be able to go look at the 'reference Eos' in my VW dealer showroom to find out if there are any antennas on any of the glass. Perhaps someone could investigate a North American model and post their findings here. Also, have a look at the position of the rear window when the top is open, and see if it is proximate to the antenna assembly in the trunk lid - maybe that might be the reason for that reference, who knows.
Michael


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## PanEuropean (Nov 3, 2001)

*Re: TB: Radio, Premium Sound System (PanEuropean)*

I just did further investigation, and found that the Panasonic Premium Sound System (to which the TB refers) is installed in several different VW products, not just the Eos... hence the very valid warning about window film, because the other cars have antennas embedded in the window glass.
Which takes me back to the big general caution I posted in the introductory post about TBs, Eos Technical Bulletins (TB) - Philosophy, How to Use, Index, where I wrote that the VW staff may often know more that we as enthusiasts know... so, we need to be pretty careful before we jump on something.
Michael


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## sweatyworker (May 4, 2005)

*Re: TB: Radio, Premium Sound System (Shaka)*


_Quote, originally posted by *Shaka* »_
Didn't we determine all the antenna are in the plastic trunk lid, and hence window tint should play no role?!

Sorry to bump this. Are there any photos or further information on the antenna in the EOS, both Radio and Nav?


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## PanEuropean (Nov 3, 2001)

*Re: TB: Radio, Premium Sound System (sweatyworker)*

The antennas are all in the trunk lid. The Navigation system and Satellite Radio (XM / Sirius) antennas are in the middle, the AM and FM antennas are cables that run around the perimeter of the lid, and the sensor for the compass is on the left side of the trunk lid (not illustrated). For ROW market Eos that are fitted with factory installed phones, the phone antenna is also in the trunk lid.
Michael
*Eos Antennas*


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