Tapping into stock nav/radio audio input

greiswig · **Posted:** Sun Mar 12, 2006 2:41 pm

Hi,

I have an '05 with the nav and CD changer. I have a Creative Zen MP3 player I'd like to hook into it. Doesn't look easy.

I've tried the FM transmitters, a couple different models. Close, but not quite: the closest I've come is to strip the antenna lead on the transmitter and wire it directly to the antenna in. Oddly, that lead had two wires...if both are hooked up to the antenna, there's very poor transmission. If only one is hooked up, the transmission is good, but there is an odd oscillation that occurs...about like a 60Hz hum that oscillates back and forth from left to right channels of the stereo at about 2Hz.

First, does anyone know why there are 2 antenna leads?

Second, is there a line-level audio from the CD changer to the head unit? If so, I could tap that and put it on a switch.

Thanks for any and all help...

RaeRae1616 · **Joined:** Wed Jan 11, 2006 6:23 pm **Posts:** 124

Hmmm.... is your dual antenna lead really just the signal and ground? Maybe ground feedback loop you're getting?

What about a wireless FM Transmitter? In my experience they work very nicely. If you don't want it visible you can always put it inside your dash, hard wired to the cigarette lighter or something . . . so it's always on, using an unused FM station in your area; get a digital one so you can really tune the channel it uses.

That's what I would do to leave the stock wiring in tact to prevent the noises you're hearing.

Se7enLC · **Posted:** Mon Mar 13, 2006 3:04 pm

greiswig wrote:

I've tried the FM transmitters, a couple different models. Close, but not quite: the closest I've come is to strip the antenna lead on the transmitter and wire it directly to the antenna in. Oddly, that lead had two wires...if both are hooked up to the antenna, there's very poor transmission. If only one is hooked up, the transmission is good, but there is an odd oscillation that occurs...about like a 60Hz hum that oscillates back and forth from left to right channels of the stereo at about 2Hz.

First, does anyone know why there are 2 antenna leads?

Antennas are coaxial, and you definitely can't splice them together like that!

What you want is a Wired FM Modulator. It'll be a box that couples inline with the antenna and has an aux input cable. It will act like what you are trying, but will be a closed box with shielding to prevent that sort of interference.

Crutchfield page on Wired FM Modulators
Another Crutchfield page on FM Modulators
Some random site with FM Modulators

greiswig · **Posted:** Mon Mar 13, 2006 11:34 pm

Thanks for the input, guys. Didn't know wired modulators existed. I'd still rather tap into the CD changer audio input, just to avoid yet another conversion (to FM), but for the prices, these are probably worth a shot.

Se7enLC · **Posted:** Tue Mar 14, 2006 1:02 am

I took a look in the factory service manual for the 2005. Here's what it says for the Radio -> CD Changer connection:

1 Audio MUX Right
6 Audio MUX Left
2 Shield
7 Ground
10 Fused 8
5 Ignition/Run ACC Output
3 Audio Return
4 PCI Bus

if I didn't see "MUX" in there, I would say that you should be able to use Left, Right, and Return to act as an input on a switch like you suggest. But if the signals are multiplexed, chances are there's no way to connect the raw audio into that line. (MUX sort of implies a time or frequency-domain digital multiplex on the line, so adding audio would just make noise)

greiswig · **Posted:** Tue Mar 14, 2006 2:03 am

Se7enLC wrote:

I took a look in the factory service manual for the 2005. Here's what it says for the Radio -> CD Changer connection:

1 Audio MUX Right
6 Audio MUX Left
2 Shield
7 Ground
10 Fused 8
5 Ignition/Run ACC Output
3 Audio Return
4 PCI Bus

if I didn't see "MUX" in there, I would say that you should be able to use Left, Right, and Return to act as an input on a switch like you suggest. But if the signals are multiplexed, chances are there's no way to connect the raw audio into that line. (MUX sort of implies a time or frequency-domain digital multiplex on the line, so adding audio would just make noise)

Perfect. Well, the advise, anyway. It's fantastic that someone with the electronics knowledge and the SM helped me out on this. I wish you'd had better news for me, but...hey, at least now I know what I can't do. I'll look into getting a dedicated, wired FM modulator. Thanks again!

Taz · **Posted:** Tue Mar 14, 2006 7:51 am

greiswig wrote:

Hi,

I have an '05 with the nav and CD changer. I have a Creative Zen MP3 player I'd like to hook into it. Doesn't look easy.

I've tried the FM transmitters, a couple different models. Close, but not quite: the closest I've come is to strip the antenna lead on the transmitter and wire it directly to the antenna in. Oddly, that lead had two wires...if both are hooked up to the antenna, there's very poor transmission. If only one is hooked up, the transmission is good, but there is an odd oscillation that occurs...about like a 60Hz hum that oscillates back and forth from left to right channels of the stereo at about 2Hz.

First, does anyone know why there are 2 antenna leads?

Second, is there a line-level audio from the CD changer to the head unit? If so, I could tap that and put it on a switch.

Thanks for any and all help...

Do you get the oscillation when you use the transmitter as designed or just when you hook the antenna wires together? The reason I ask is that I just started getting an oscillation with my FM transmitter for an Ipod. I never had it when I had the transmitter in my old truck and I found it odd that I would get it in the CRD because it sounds like something that you would get with a spark ignition. I was thinking that my FM transmitter might be going out but now I wonder since you are experiencing something like it with a CRD also.

greiswig · **Posted:** Tue Mar 14, 2006 4:16 pm

[quote="Taz
Do you get the oscillation when you use the transmitter as designed or just when you hook the antenna wires together? The reason I ask is that I just started getting an oscillation with my FM transmitter for an Ipod. I never had it when I had the transmitter in my old truck and I found it odd that I would get it in the CRD because it sounds like something that you would get with a spark ignition. I was thinking that my FM transmitter might be going out but now I wonder since you are experiencing something like it with a CRD also.[/quote]

Taz,

I get it when hooking one transmission antenna lead directly to the receiving antenna at the head. It clearly pans back and forth between L and R channels...something that ignition noise wouldn't do, AFAIK.

Good luck!

Taz · **Posted:** Wed Mar 15, 2006 7:28 am

I was sitting beside a Toyota Prius today and mine was making a noise through the speakers and I thought, could that Prius battery pack or electric motors give off enough EMF to interfere with my FM transmitter, But as it turns out I think that is is somehow connected to my lights, because as soon as I took my foot off of the brake the noise went away. I later noticed that it also happens when the left turn signal light is on, but not when the right is on. Anyways doesn't sound like the same problem you are having.

Se7enLC · **Posted:** Wed Mar 15, 2006 11:03 am

Taz wrote:

I was sitting beside a Toyota Prius today and mine was making a noise through the speakers and I thought, could that Prius battery pack or electric motors give off enough EMF to interfere with my FM transmitter, But as it turns out I think that is is somehow connected to my lights, because as soon as I took my foot off of the brake the noise went away. I later noticed that it also happens when the left turn signal light is on, but not when the right is on. Anyways doesn't sound like the same problem you are having.

From what I've heard, the Jeep is very electrically noisy. I went with a wired connection to my iPod, and I have no problems.

Taz · **Posted:** Wed Mar 15, 2006 9:56 pm

Se7enLC wrote:

Taz wrote:

I was sitting beside a Toyota Prius today and mine was making a noise through the speakers and I thought, could that Prius battery pack or electric motors give off enough EMF to interfere with my FM transmitter, But as it turns out I think that is is somehow connected to my lights, because as soon as I took my foot off of the brake the noise went away. I later noticed that it also happens when the left turn signal light is on, but not when the right is on. Anyways doesn't sound like the same problem you are having.

From what I've heard, the Jeep is very electrically noisy. I went with a wired connection to my iPod, and I have no problems.

I'm thinking about the wired connection that lets you use the stearing wheel controls, I'm kind of waiting for the new Ipod video to see what connection it will have on it. I might have to trade up my Ipod gen 3 for a video ipod.

Se7enLC · **Posted:** Thu Mar 16, 2006 9:55 am

Taz wrote:

I'm thinking about the wired connection that lets you use the stearing wheel controls, I'm kind of waiting for the new Ipod video to see what connection it will have on it. I might have to trade up my Ipod gen 3 for a video ipod.

Pretty sure iPod is planning on staying compatible with the dock connector. I have a 4G and love it. It has a b+w screen and none of the photo/video stuff, but it works great and I'm happy with it.

Tapping into stock nav/radio audio input

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