XM Radio Install Problem

[asuyak]

Ok so I've installed this XM radio. So I turn on my car and listen to the preview channel, ok it's all good. But wait I turn off the XM radio and try to listen to some of the weaker FM channels and they are full of static now. If I stay in one place I can usually hear them for a bit but if I'm driving it fades in and out. I still get the stronger FM stations fine though. So what the heck did I do? I've double checked the antenna plugs and made sure that they are nice and snug, but it didn't do anything. Any ideas? Thanks.

[MarvelPhx]

The FM modulator should become transparent when the unit is off, but I can see how it would affect lower strengh station just by design.

If you can, I would recommed installing one of the CD Changer input converters for your XM unit.

[morcheeba]

I know that the E46 has an antenna pre-amp on the driver's side C-pillar. I'm not sure how this gets its power (I'll have to look it up on the CD), but the usual trick used in radios is to power the amplifier with a DC voltage on the antenna lead. Yes, it sounds weird - power going into the amplifier and signal coming back on the same wire - but it works well.

Anyway, if the preamp is powered this way and if if the XM antenna splitter doesn't pass the power onto the amplifier (easily conceivable), then you'd probably see exactly what you're seeing. The solution would be to put a power injector between the antenna preamp and the XM splitter:


(radio)--(XM)--(injector)--(preamp)--(antenna)
| |
box +12v


Usually the XM splitter would reject this power; you might need an isolater, too, between the injector and the XM:


(radio)--(XM)--(isolator)--(injector)--(preamp)--(antenna)
| |
box +12v

Here's where a multimeter would be really handy. Measure the DC voltage at either side of the radio; if it's zero, then there isn't some power-injection scheme going on and you can disregard everything I said (possible!). If it's not zero and it's a substantially different value (especially zero!) on the other side of the XM switch, then you've probably found the problem.

If you're lucky, then there is some sort of "antenna power" or "power injector" switch/jumper on the XM hardware that you can enable.

What brand XM receiver are you using? Maybe someone else here has the same type and you can see if it is a design vs. installation problem.

<font size=-1>[ This Message was edited by: morcheeba on 2003-03-17 18:25 ]</font>

[asuyak]

The model I have is the Pioneer GEX-FM903XM. It's the same one as Marvel's. As for getting around the FM modulation is there a brand that people like better? the two that keep popping up are blitzsafe and soundgate. I have also noticed that the reason why my radio stops working is because there is an obstruction in the way. Like on the freeway it's fine because there are no houses, however if there is a freeway overpass that I go under the radio(FM) cuts out. Don't know if that means anything more than I have a weak antenna now. Thanks for the help so far.

[morcheeba]

If it's the same as Marvel's, then there goes my theory /forums/images/smiles/icon_frown.gif ...and I had so much fun drawing those pictures!

[asuyak]

Ok so just to test my antenna again, I took out the XM radio leads and what not and in theory returned it to the way it used to be. This still however did not help my radio reception. So what could I have done to ruin the antenna? The connector still feels snug so I don't think I somehow tweaked the antenna connector at all. I would love some help on this. Thanks.

[morcheeba]

ugh... I hate it when I break something that I'm trying to fix. Three options:

- radio receiver messed up (desensitized, maybe by static electricity)
- cable messed up. RF cables are touchy, but this isn't exactly rocket science (if it was a 100W transmitter, I'd be more worried about this)
- pre-amp messed up (desensitized or killed by static) It may not be getting power (which, like I said in my last post, I don't really know how it gets its power)

Here's a link on checking the connector at the preamp side... It mentions only AM, but I suspect that FM is also amplified (just a guess). How is your AM reception?

E46 Radio Noise on AM Band,Poor AM Reception (http://www.openbmw.org/downloads/65 01 99 - SI E46 Radio Noise on AM Band,Poor AM Reception.pdf)

See also Removing and installing or replacing antenna amplifier (http://www.openbmw.org/downloads/65 24 010 - RA Removing and installing or replacing antenna amplifier.pdf)

Once you pull out the C-piller, everything should be visible. Unfortuantly, you'll need some test equipment to debug the 3 possibilities above. The radio has a signal-strength indication (hidden in the diagnostic menu), but you already know it has a weak signal. Proper servicing would be to inject a known quantity signal and see if it makes it through the preamp, then the cable, and then into the radio. But, in the absence of these things, you might just have to swap parts... if you're lucky, you may have an extra cable-tv cable with the same connector that you can easily swap in for the car-harness-cable. Lastly, as a sanity check, make sure that the pin inside the connector hasn't broken.

Good luck, wish I could help more!

[asuyak]

Ok well now I feel dumb.... That pin inside the antenna connector on the radio was bent so it wasn't getting a connection at all. I guess in my haste I just didn't notice doing that. So I carefully bent it back and now no more antenna problems. Who woulda thought? Thanks for all the help Morcheeba.

[HiMiles]

Morcheeba, how did you get the CD to print onto a .pdf file? I would really appreciate if you can teach me how to do that on mine. Thanks

P.S.: I'm glad the antenna problem is fixed by the way. So no hijacked thread anymore, right?

[morcheeba]

I didn't do the conversion to PDF; someone on that website did. Either they have an inside source, or they used the print function on the CD, and their printer was Acrobat Distiller. I tried deciphering the CD (hoping to find a directory of .pdf's), but I guess they use their own format so that the text in be in so many languages...