Help me understand fm modulator.
 

I want to get one of those 399 video only units for my nav. They told me to get sound I must use an fm modulator. Can anyone explain how I would have to hook this up?

That just means you will get the components to "broadcast" a weak FM signal in your car. FM modulators are very inexpensive. You just run the audio into the FM Mod and then tune your stereo to a preset, unused station to listen to your DVD audio. It is totally wireless. Sound quality will be fine for basic movie watching but it is not for people who like really good sound. Signal to noise ratio is not good when you do it that way and other FM signals can interfere. Fine for some people, not for me.

For better sound connect the the audio-out on the $399 video unit and run it into the Auxiliary input. This requires a $35 add-on aux kit but the sound is much better.

That's my .02 cents.

I would love to do the aux input but I was told that my 8/01 build i couldn't get that unless i upgraded my radio module.

That is true, didn't know you had an '01. I had to change the radio module in mine as well to get Aux (and Sirius) capability. Since FM mod is cheap you can always try that first and see if it is good enough for you. You can always change it later to something better.

Going the FM modulation route is a "cheap and dirty" method, and while it is easy to do, you usually pay for it in sound quality. There are several alternatives for putting in an AUX input to your vehicle:

1. Upgrade your radio module to a 2003 or newer so that you can get the native AUX input (I did this on my 2001 X5 and it worked out great)

2. Install an aftermarket AUX input solution, such as from Blitzsafe or Soundgate. These typically plug in at your CD changer connection.

3. If you have Nav, make an AUX input from your tape player source.

The blitzsafe and soundgate solutions both say they do not work with DSP so that is out. I am wondering how much different the fm modulator would sound from the tape method. If I could find a good deal on a new radio module I would do that but I have yet to do so.

I thought Blitzsafe and Soundgate both had adaptors that work with DSP.

I picked up a 2003 radio module for $200, which could be a better buy if you can locate one.