Go Back  CorvetteForum - Chevrolet Corvette Forum Discussion > General Corvette Topics > Audio/Electronics
Reload this Page >

How many installed their C6 aftermarket HU antenna INCORRECTLY, but don't know it!!!

Notices
Audio/Electronics Stereo System Installation Info, Amplifiers, Subwoofers, Radar Detectors, Police Scanners, and CB Radios for the Corvette

How many installed their C6 aftermarket HU antenna INCORRECTLY, but don't know it!!!

 
Old 09-05-2006, 10:37 AM
  #1  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default How many installed their C6 aftermarket HU antenna INCORRECTLY, but don't know it!!!

There seems to be a VERY COMPLEX antenna design in the new C6 vette compared to "traditional" cars. People with aftermarket HU's need to "phantom feed power for the diversity atenna setup" (from what I've been told) to retain the best AM/FM reception. WHO DID THIS AND HOW DO YOU DO IT???????????


WRITTEN BY shopdog:
There are 3 entertainment radio antennas located in the rear fascia. One is for AM, the other two provide diversity reception for FM (diversity reception minimizes FM flutter in a moving vehicle). The antennas themselves are just insulated wires. There are two modules in the rear fascia. One acts as an AM preamp, and the other implements FM diversity. There are coaxial cables connecting the two modules, and a coaxial cable running from the diversity module up front to the radio.

If you remove a tail light, you can see the wires. If you remove the rear hatch trim, you can see the modules. The coax running to the radio is routed in the wiring channel along the driver's side of the car.

WRITTEN BY shopdog
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.
MAGRED2001VETTE is offline  
Old 09-05-2006, 03:53 PM
  #2  
LS WON
CF Senior Member
 
LS WON's Avatar
 
Member Since: Dec 2002
Location: San Francisco CA
Posts: 30,675
Received 81 Likes on 79 Posts
Default

Originally Posted by MAGRED2001VETTE
There seems to be a VERY COMPLEX antenna design in the new C6 vette compared to "traditional" cars. People with aftermarket HU's need to "phantom feed power for the diversity atenna setup" (from what I've been told) to retain the best AM/FM reception. WHO DID THIS AND HOW DO YOU DO IT???????????


WRITTEN BY shopdog:
There are 3 entertainment radio antennas located in the rear fascia. One is for AM, the other two provide diversity reception for FM (diversity reception minimizes FM flutter in a moving vehicle). The antennas themselves are just insulated wires. There are two modules in the rear fascia. One acts as an AM preamp, and the other implements FM diversity. There are coaxial cables connecting the two modules, and a coaxial cable running from the diversity module up front to the radio.

If you remove a tail light, you can see the wires. If you remove the rear hatch trim, you can see the modules. The coax running to the radio is routed in the wiring channel along the driver's side of the car.

WRITTEN BY shopdog
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.
Sounds like I have one of these problems going on.
LS WON is offline  
Old 09-05-2006, 05:26 PM
  #3  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by LS WON
Sounds like I have one of these problems going on.
I think most people on here do and don't even realize that their AM/FM signal SUCKS (or not as good as could be) due to the complex design of the C6 antenna setup NOT BEING HOOKED UP PROPERLY TO THEIR AFTERMARKET HU! You can't just buy a simple GM antenna adaptor for the dash coax and plug into the back of your new HU. Otherwise your antenna will only be the 8 feet of coax to the back of the vette. Not very effecient. More needs to be done.....HELP!

I'm in need of some serious people who have experience with active antenna setups.
MAGRED2001VETTE is offline  
Old 09-05-2006, 07:34 PM
  #4  
TheKomoman
CF Senior Member
Support Corvetteforum!
 
TheKomoman's Avatar
 
Member Since: Jun 2004
Location: Skippack PA
Posts: 9,289
Received 8 Likes on 7 Posts
St Jude Donor '13
Default

Originally Posted by MAGRED2001VETTE
I think most people on here do and don't even realize that their AM/FM signal SUCKS (or not as good as could be) due to the complex design of the C6 antenna setup NOT BEING HOOKED UP PROPERLY TO THEIR AFTERMARKET HU! You can't just buy a simple GM antenna adaptor for the dash coax and plug into the back of your new HU. Otherwise your antenna will only be the 8 feet of coax to the back of the vette. Not very effecient. More needs to be done.....HELP!

I'm in need of some serious people who have experience with active antenna setups.
Here's a scan of the antenna schematic from the SM for '06. The "FM Composite Signal" and "Antenna Enable Signal" are likely the connections you're in search of. As to what to do with them... um....

You may have problems answering this question for a couple of reasons. The first is it's pretty technical and the answer may not be known yet. The second is that, and I do not intend this to be a flippant response, it's unlikely that someone who has gone through the expense and effort it takes to replace the head unit likely did it to listen to AM or FM radio. So there may simply not be enough interest to generate an answer.
Attached Images  
TheKomoman is offline  
Old 09-06-2006, 02:00 AM
  #5  
LS WON
CF Senior Member
 
LS WON's Avatar
 
Member Since: Dec 2002
Location: San Francisco CA
Posts: 30,675
Received 81 Likes on 79 Posts
Default

Originally Posted by MAGRED2001VETTE
I think most people on here do and don't even realize that their AM/FM signal SUCKS (or not as good as could be) due to the complex design of the C6 antenna setup NOT BEING HOOKED UP PROPERLY TO THEIR AFTERMARKET HU! You can't just buy a simple GM antenna adaptor for the dash coax and plug into the back of your new HU. Otherwise your antenna will only be the 8 feet of coax to the back of the vette. Not very effecient. More needs to be done.....HELP!

I'm in need of some serious people who have experience with active antenna setups.
Well I have tried the AF switch and the switching from Am to FM and back but finally we took another Corvette and parked it next to mine tuned it to the same station and you could hear that station find on the other car. Mine didn't even pick it up. So dealership will do their thing soon to fix it or diagnose it or replace it.
LS WON is offline  
Old 09-07-2006, 02:40 AM
  #6  
LS WON
CF Senior Member
 
LS WON's Avatar
 
Member Since: Dec 2002
Location: San Francisco CA
Posts: 30,675
Received 81 Likes on 79 Posts
Default

LS WON is offline  
Old 09-18-2006, 03:08 PM
  #7  
C6VetteRocks
CF Senior Member
 
Member Since: Oct 2005
Posts: 224
Likes: 0
Received 1 Like on 1 Post
Default Took the 60 Seconds

Originally Posted by TheKomoman
Here's a scan of the antenna schematic from the SM for '06. The "FM Composite Signal" and "Antenna Enable Signal" are likely the connections you're in search of. As to what to do with them... um....

You may have problems answering this question for a couple of reasons. The first is it's pretty technical and the answer may not be known yet. The second is that, and I do not intend this to be a flippant response, it's unlikely that someone who has gone through the expense and effort it takes to replace the head unit likely did it to listen to AM or FM radio. So there may simply not be enough interest to generate an answer.
Took longer to find the schematic page in the manual (my home system doesn’t show thumbnails and I first saw this on another system, so I could not see the page) then it did to find the information. A minute and 22 pages later I found the debug instructions for the antenna. In a real summarized form:

The Antenna Enable needs B+ (battery voltage) to turn on the antenna module.

The radio supplies 5v to 8v on the FM Composite wire to switch to FM. Looks like 0v is for AM reception. Also over 8v is not acceptable since 0V, B+, or Ground is cause for FM Failure.

So to allow the antennas to work correctly you need to supply 12v to the Antenna Enable and 5v to 8v to the FM Composite. The still unknown factor, without the Nav radio schematic is current and termination.
C6VetteRocks is offline  
Old 09-18-2006, 03:40 PM
  #8  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by C6VetteRocks
Took longer to find the schematic page in the manual (my home system doesn’t show thumbnails and I first saw this on another system, so I could not see the page) then it did to find the information. A minute and 22 pages later I found the debug instructions for the antenna. In a real summarized form:

The Antenna Enable needs B+ (battery voltage) to turn on the antenna module.

The radio supplies 5v to 8v on the FM Composite wire to switch to FM. Looks like 0v is for AM reception. Also over 8v is not acceptable since 0V, B+, or Ground is cause for FM Failure.

So to allow the antennas to work correctly you need to supply 12v to the Antenna Enable and 5v to 8v to the FM Composite. The still unknown factor, without the Nav radio schematic is current and termination.
I just read it 3 times! And can say, I don't think there is more than 2 people that have done/understand this in the world yet!

Last edited by MAGRED2001VETTE; 09-18-2006 at 03:54 PM.
MAGRED2001VETTE is offline  
Old 09-18-2006, 06:37 PM
  #9  
LS WON
CF Senior Member
 
LS WON's Avatar
 
Member Since: Dec 2002
Location: San Francisco CA
Posts: 30,675
Received 81 Likes on 79 Posts
Default

Originally Posted by C6VetteRocks
Took longer to find the schematic page in the manual (my home system doesn’t show thumbnails and I first saw this on another system, so I could not see the page) then it did to find the information. A minute and 22 pages later I found the debug instructions for the antenna. In a real summarized form:

The Antenna Enable needs B+ (battery voltage) to turn on the antenna module.

The radio supplies 5v to 8v on the FM Composite wire to switch to FM. Looks like 0v is for AM reception. Also over 8v is not acceptable since 0V, B+, or Ground is cause for FM Failure.

So to allow the antennas to work correctly you need to supply 12v to the Antenna Enable and 5v to 8v to the FM Composite. The still unknown factor, without the Nav radio schematic is current and termination.
Wouldn't it be just as effective to just replace the antenna modules?
LS WON is offline  
Old 09-18-2006, 06:38 PM
  #10  
LS WON
CF Senior Member
 
LS WON's Avatar
 
Member Since: Dec 2002
Location: San Francisco CA
Posts: 30,675
Received 81 Likes on 79 Posts
Default

Originally Posted by MAGRED2001VETTE
I just read it 3 times! And can say, I don't think there is more than 2 people that have done/understand this in the world yet!

Just replace defective parts.
LS WON is offline  
Old 09-19-2006, 02:28 PM
  #11  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by LS WON

Just replace defective parts.
We're talking about people who have an aftermarket HU (like Alpine) that are trying to hook it up to the factory AM/FM antenna setup, but did so incorrectly because they did not hook up the power also to the antenna module or something....
MAGRED2001VETTE is offline  
The following users liked this post:
Formula8 (04-16-2019)
Old 09-19-2006, 02:34 PM
  #12  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by C6VetteRocks
The Antenna Enable needs B+ (battery voltage) to turn on the antenna module.

The radio supplies 5v to 8v on the FM Composite wire to switch to FM. Looks like 0v is for AM reception. Also over 8v is not acceptable since 0V, B+, or Ground is cause for FM Failure.

So to allow the antennas to work correctly you need to supply 12v to the Antenna Enable and 5v to 8v to the FM Composite. The still unknown factor, without the Nav radio schematic is current and termination.
ANYBODY KNOW....
What is the FM Composite?
What is the size resistor needed to drop the voltage or if current varries, do we need a voltage regulator set at ~7volts?
What wire color to hook up to?
MAGRED2001VETTE is offline  
Old 09-19-2006, 06:22 PM
  #13  
pentavolvo
CF Senior Member
 
pentavolvo's Avatar
 
Member Since: Nov 2004
Location: Dyer IN
Posts: 8,718
Received 15 Likes on 15 Posts
Cruise-In IX Veteran
Default

Ok I can only semi answer your question in C5 coupes there is a similar issue with supplying 5 volts or something to power up the antenna booster, what guys have used is like a cell phone charger or something like that from radio shack just wire to 12volts behind the radio then splice the 7volt output to the proper wire
pentavolvo is offline  
Old 09-20-2006, 12:48 AM
  #14  
LS WON
CF Senior Member
 
LS WON's Avatar
 
Member Since: Dec 2002
Location: San Francisco CA
Posts: 30,675
Received 81 Likes on 79 Posts
Default

LS WON is offline  
Old 09-23-2006, 10:01 PM
  #15  
C6VetteRocks
CF Senior Member
 
Member Since: Oct 2005
Posts: 224
Likes: 0
Received 1 Like on 1 Post
Default More info

Antenna Enable Signal is a 12v signal that not only enables the Antenna Module, it also enables the BOSE amp and the BOSE Premium subwoofers. Each of which have a 12V power source controled by the Retained Assessory Power. At the head unit, the wire information is:
Connector C1
Pin B3
Color White
Circuit 1487

FM Composite Signal is the 5v to 8v FM antenna enable signal. The wire information is:
Connector C1
Pin A4
Color Yellow
Circuit 5172

Head Unit C1 Connector Top Front (non-wire) Side
________________________________________ __________
| A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | A9 | A10 | A11 | A12 |
|------------------------------------------------------------------- |
| B1 | B2 | B3 | B4 | B5 | B6 | B7 | B8 | B9 | B10 | B11 | B12 |
---------------------------------------------------------------------
C6VetteRocks is offline  
The following users liked this post:
Formula8 (04-16-2019)
Old 09-25-2006, 04:41 PM
  #16  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

THANKS, thats exactly what I needed! The 12v source is not a problem, but where would I go for a regulated 5-8v for pin A4?

I truely wounder out of the thousands of people and install shops that do Corvettes, how many hook up the vette antenna wrong!

Last edited by MAGRED2001VETTE; 09-25-2006 at 04:58 PM.
MAGRED2001VETTE is offline  
Old 09-25-2006, 04:59 PM
  #17  
pentavolvo
CF Senior Member
 
pentavolvo's Avatar
 
Member Since: Nov 2004
Location: Dyer IN
Posts: 8,718
Received 15 Likes on 15 Posts
Cruise-In IX Veteran
Default

you need to either get a small cigarette power supply think or find a voltage stepper downer of sorts... find nerdy kid at radio shack and talk to him
pentavolvo is offline  
Old 10-02-2006, 12:41 AM
  #18  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

MAGRED2001VETTE is offline  
Old 10-06-2006, 11:20 AM
  #19  
wratran
CF Senior Member
 
Member Since: Mar 2006
Location: dallas tx
Posts: 754
Likes: 0
Received 0 Likes on 0 Posts
Default

It is strange to hear all this FM signal issue. I have an 06 w/ factory base system. I replaced the HU with Pioneer D2, and plug it directly into the antenna plug with an adapter. The signal is perfectly clear on all stations ...both FM and AM.
wratran is offline  
Old 10-07-2006, 12:21 AM
  #20  
MAGRED2001VETTE
CF Senior Member
Thread Starter
 
Member Since: May 2003
Location: College Station TX
Posts: 822
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by wratran
It is strange to hear all this FM signal issue. I have an 06 w/ factory base system. I replaced the HU with Pioneer D2, and plug it directly into the antenna plug with an adapter. The signal is perfectly clear on all stations ...both FM and AM.
Just imagine how much better it would be if your "powered antenna modual" would have been supplied voltage correctly.
MAGRED2001VETTE is offline  

Thread Tools
Search this Thread
Quick Reply: How many installed their C6 aftermarket HU antenna INCORRECTLY, but don't know it!!!


Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: