2006 s40 Antenna Cable Spec Question - FM Modulator

Post by **DWeisbrod** » 04 Jan 2014, 16:31

So I've been spending a lot of time experimenting with my s40's base sound system and an FM modulator. I've seen all the posts on various forums about finding the "9v" tab connector at the rear windshield, or finding the connector in the driver's footwell, etc, etc.

So, here's the question - Why two cables? Why not one? In every other car I've ever seen, the antenna cable is a single co-ax with just an inner wire and an outer wire. This Volvo has TWO co-ax cables with an inner wire and an outer sheathing wire. Why? What's the advantage/difference?

The reason why I am asking is because I want to cut into the antenna cable and introduce my FM modulator signal as close to the stereo as possible, for better quality sound. As I was testing the "9v" setup, I found out that even though my FM modulator is supposed to cut out the regular antenna signal when it's turned on, I was still able to get some radio signals because of the fact that the antenna wires that run through the car were still picking up the radio signals.

Based upon what I know about the "9v" setup, I think - tentatively- that I should solder the center wire of the new antenna cable to the center of one wire, and the outer sheathing wire to the sheathing of the other wire. But I'm not sure about that, so I'm looking for a little help...

Thanks, everyone!

Dave

Post by **DWeisbrod** » 04 Jan 2014, 16:33

By the way, if you're interested, here is the link to the post I found describing the "9v tab" method...

http://www.volvo-forums.com/t17221-07-s ... ntenna.htm

mf70 · Post by **mf70** » 20 Feb 2014, 15:09

The two cables are there because the output of the antenna amp (16/16 in Volvo docs) is sent to two places (potentially): The AM/FM tuner itself (16/94) and the Traffic Message Channel Module (16/49) if installed.

In addition, I believe that line 2 into the amp carries the 12V supply from the tuner to the amp. Therefore, an FM Modulator inserted between the amp and the receiver would have to pass both the 12V and the signal to avoid blocking all FM from the amp.