I've had my c^ for one week now. I noticed the radio reception is not that great. AM is terrible and XM cuts out more often than it does on other vehicles I have with factory XM. FM radio seems okay. I was wondering if it has something to do with the antenna being incorporated into the spoiler (that's what the dealer told me) or maybe I just have a bad antenna.

 

XM antenna is in the outside rear-view mirrors.

I have no problem with mine.

 

Is it passenger side or both ? If its passenger, it would explain why I lost XM signal where I did ... heavily wooded on right side of the road.

But AM still stinks.

 

IIRC it is in the driver's side mirror. But that can still make sense depending on your direction of travel. The XM sats are in the Southwest sky. If you were heading South or Southeast then you would have the trees and the car itself between you and the sat.

 

My c6 AM/FM reception is the best yet, better then 03, and 04. The previous post is correct, on XM if the antenna is blocked from a view to the south, it is going to cut out.

 

No antennas in the spoiler, dealer is a moron. The 2006 and 2007 C6 has the XM antenna(s) in the outside rearview mirrors (2005 had a wart on the roof). The two dual diversity FM antenna elements are in the rear fascia, as is the single voltage probe AM antenna.

All of these antennas are active antennas. The XM antennas have LNB block downconverters built in, the FM diversity module has preamps and switching built in, and the active AM antenna has a FET source follower. The modules containing the active electronics for the FM and AM antennas are accessible by removing the rear interior trim panel. If power is lost to a module, or a module is defective, you'll have very poor or no reception.

Poor XM reception in rural areas is to be expected if the antennas don't have a clear view of the southern sky. Hills, buildings, or even heavy vegetation, can block the signal. In most urban areas, XM has terrestrial repeaters to fill in for signal loss due to urban clutter. Sometimes these repeaters are out of service. It isn't uncommon to suddenly find you can't receive a signal in areas which worked before, then in a few days the signal is back. That's simply because the repeater for that area was down, and was then repaired.

Dual diversity virtually eliminates multipath flutter on FM signals. If you get lots of flutter on weak signals, suspect one of the FM antennas is broken. If all signals are weak, suspect that the diversity module has failed.

AM reception in a plastic car is problematic. The wavelengths of AM broadcast signals are so long that there are only two sorts of practical antennas, the ferrite loaded loop, or the voltage probe. Since loop antennas are directional, they aren't suitable for a car, so voltage probe it is. The voltage probe antenna works by sensing the potential difference of the EM wave between ground and a point located above ground. Normally, the metal car body is used as the RF ground (its capacitance to true Earth supplies the RF ground connection). But the Corvette doesn't have a metal body, so the frame is used. The frame isn't nearly as large a capacitor plate as a metal body, so while it works, it doesn't work exceedingly well. A bad frame ground connection to the AM module will result in very poor AM reception.

In some early 2005 cars a wiring mistake resulted in the AM module being connected to the HU FM input and the FM module being connected to the HU AM input. This resulted in very poor AM and FM reception. Since your FM works, this isn't your problem.

Most likely you have a bad ground connection to the AM module. Probably a failure to bite through the paint where the wire attaches to the frame, or possibly a cross threaded screw that didn't tighten down on the wire enough to make good electrical contact.

For completeness, I'll also note that in 2005 models equipped with Nav, a software error could result in the FM module not being powered. Switching to AM and then back to FM would temporarily cure this problem. A software update was released which permanently fixed this issue (and also gave us MP3 capabilities). Since I assume you have a 2007, this shouldn't be an issue for you.

In summary, I have to say that your XM issues are probably just the nature of the beast. Your AM issue is most likely a poor connection to frame ground, though it could be that you're just expecting too much from an AM antenna in a plastic car.

 

Any idea where the ground point(s) are?
Thanks

 

 

if this is true what is the rectangular box next to my rearview mirror.

 

Shopdod
I want to install a wired FM modulator that cuts out the FM antenna (thus blocking FM reception) and would enable me to play my iPod trough the FM radio, without getting interference from FM stations. Which interior trim panel should I remove to get at the FM antenna to wire in the modulator?

 

Onstar

 

that is your SAT NAV box

 

No like mentioned before it’s the OnStar antenna. The stock Nav system uses a GPS antenna that is under the dash.

 

Do you have Rear LED's? If so you need a ferrite core on green Antenna Wire.You also may need or try putting one at back of head unit for XM wire and seeing back there add to other wire. I dont use XM so mine is located behind tails on green antenna wire

 

this is a 17 year old thread lol

 

LOL OMG Talk about late to the game! lol

 

that explains why someone is using the radio for AM reception.