Peter_Reinhard

Hello.
My radio reception is very poor. I get a couple of FM stations, none well, and maybe one AM station. I bought my 08 coupe with an aftermarket Sony Nav/Radio system the previous owner installed. I'm wondering if they didn't wire it correctly.

The radio does accept blue tooth and I can play Pandora, Tune-in Radio, etc through it, but I'd like the plain old radio to work too. (The NAV works great)

I've read a bunch of posts. The antennas are in the rear facia, use a combiner for 2 FM and 1 AM antenna (I think).

So I found two modues that are GM Antenna Assemblies, one large and one small.

The large one looks like it has a connection to the larger wiring harness, and a connection to the smaller module, a Red wire that looks like an antenna going into the rear panel, and power.

The smaller assy has a green wire, also going into the rear panel which assume is the other antenna FM.

So where is the AM antenna? I hear it needs a good ground but not sure where that ground is. The AM actually works "ok" and that may be all you get in this type of car.

Regarding FM, As a test, I turned on the FM radio to a station, then unplugged the power connector to the larger module, and nothing changed, making me think there is no power, or the module is bad.

Any ideas what to trouble shoot next? I've taken the console apart a few times but hate doing it because of those connectors but I'll do it if necessary. Do you think an aftermarket Sony will not activate the antenna modules and I'll have to rig up power somehow?

Thanks for your help.

markcz

With very few exceptions aftermarket radios just get crappy reception in C6

If you're using the stock amp/speaker setup then the power wire for the antenna module has power. If you have an external aftermarket amp it may not be. One it's powered, not much more you can do.

Many have had success with the antenna, and some have had good results with the stock antenna and this booster: http://www.ebay.com/itm/Car-Antenna-Radio-FM-AM-Signal-Amp-Amplifier-Booster-/220831228507

LT1 Z51

My Stock Antenna has been fine, once I gave it power. This is something you MUST do or else the antenna is garbage!

Peter_Reinhard

Agree LS3 MN6 that I'll bet that the aftermarket Sony XNV77BT/Tom Tom Radio/Nav/etc unit may not be activating the antenna. I'd like figure out how to trouble shoot it.

So I'm looking at a schematic that markcz posted in 2006, Radio/Navigation System Schematics (antennas..). You provided a great explanation of the dual diversity combining FM antenna system.

The diagram shows an Antenna Enable Signal and Radio Antenna Module Signal, both going between the larger antenna module and the Radio unit. Q: What is the difference?

(I read something about a variable signal, 0V to 5VDC, and +12 VDC in one of your posts?).

General Q: if you had this Sony system already in your car, which must have been good in its day (I have a 2008 Z61 coupe, not sure when radio was installed), what would YOU do? The navigation works like a Tom Tom (pretty good), it has blue tooth and a mic for hands-free phone, my smart phone connects to it and plays audio too, but the actual user interface is real crappy through a slow-acting touchscreen. Also has inputs for cameras, auxiliary, and other stuff.

Is there a way to activate the antenna electronics either from the Sony or other external circuits? Wouldn't most aftermarket HUs not interface to the C6 antenna system like OEM does? Maybe that's what you meant; get rid of OEM and use one of those aftermarket antenna and boosters?

Thanks for the informative discussions.

LT1 Z51

I think I connected my antenna (the 12v line) to the "powered antenna" input on the HU. If you give the antenna an "ignition" powered line, then it should also work as well.

markcz

The white "antenna enable" wire is the one that needs +12v to power up the modules.

If your car still has the stock amp/speaker setup in the doors then that wire is definitely hot since it's also the one that triggers the stock amp (you wouldn't hear anything if it wasn't hot).

If you have all aftermarket amps and speakers, then there's a chance that your white wire isn't powered.

Put a volt meter on the white wire to make sure it's hot. If it's dead it will be easy to get it powered.

I believe there's speculation that the "FM composite" on the yellow wire is a varied 0-5vdc from the HU based on signal strength, but I don't recall anyone ever verifying that with a meter in C6.

You can try rigging up 5v to the yellow wire, possibly even with variable pot, but be aware that we aren't sure that's what the stock radio does. A usb power adapter should be 5v.

In my '07 I put in the $6 antenna amplifier and it worked pretty good (without it signal was crap), I moved it over to the '12 and signal is still crap with the same HU and amplifier. I listen to local radio essentially never these days, so it doesn't bother me

If it were my car, and I wanted better reception, I think I'd do the 5v experiment if I had the parts needed sitting around. If I had to spend any money I think I'd go straight to the Metra 44-UA200.

LT1 Z51

Hmm...

I had sound coming from my speakers (I have the stock amp) and my antenna was still crappy. I then sent power to another line (could be that 5 volt line) but I'm sending it 12 volts and it seems to work fine...

I need to dig up the wiring diagram (of the stock HU pinouts) and see if I can remember.

Peter_Reinhard

(I type too fast. Title should have read "Help with", not "Hello with", and whose ever heard of a Z61?)

Thanks for the replies. I'll look into getting +12 volts to the module.

The car has an aftermarket sub-woofer, kind of a nice one that fits in the left rear cubby, blended in for this particular car.

The right rear cubby has a small power amp for it so I assume this is an aftermarket unit.

If I find out about how the diversity combining works I'll report back.

Thanks again for the replies. I really hate taking the console out - done it twice - so I'll do what ever it takes working in the rear of the car. 12 volts, antenna booster, maybe new aftermarket antenna. And I don't use the radio that much either, mainly because the previous owner also put in a Borla exhaust, you know, the one that created the whole "drone" controversy. I love the sound, but on the highway it gets old. And I've done some insulation, heat and sound, and it is still way loud. The coupe rear really seems to amplify it. I'm thinking of putting some insulation in the plastic panels that surround the trunk lid - they seem to be hollow resonators, maybe that will help.
Also, a guy here on the forum built a plexiglass barrier to keep stuff from rolling from the front to the rear and reported it provided some sound mitigation. Whatever. Still love the car. It screams.

Thanks again for the advise. I'll report back someday if/when I get something to report.

Regards
Pete

markcz

C6 radio prints are HERE

LT1 Z51

B3, Antenna Enable Signal, White. I have that going to I think the "Power Antenna" line on the HU. It would be the line that normally puts a 1980's power antenna up or down.

markcz

The only difference between the HU 'power antenna' and 'remote amp trigger' wires is that the amp one is hot whenever the HU is turned on and the antenna one is only hot when it's on and playing AM/FM.

Anyone who still uses the stock amp/speakers with an aftermarket HU would connect the amp trigger to B3, so the antenna module would already be powered. If you then connect the antenna trigger wire to the yellow FM Composite wire with a 5v regulator on the line....

Peter_Reinhard

Ok, I think I understand. I don't like it, but that's what happens when you stray from OEM.

The Antenna Enable needs +12 VDC to turn on the modules.

The FM Composite is used to switch from AM to FM by applying +5 to +8 VDC.

And there are little 12/5 volt regulators out there that are and easy and cheap way to create 5 volts. (still might have to worry about EMI. Wouldn't it be funny if you built a cheap noisy circuit only to have it cause the car not to start (...i.e. KEY FOB NOT FOUND))

It sounds pretty dumb but I'm thinking of wiring a switch that comes up to my console arm rest and turn on/off 5 volts to switch between radio bands. (sounds not clean, but I could do it)

Q1) I have read that the FM Composite signal is also used to provide the modules (or radio?) a measure of signal quality. I wonder if it varies the 5 volts to 8 volts as a function of signal quality. Or if some other waveform rides over the DC. I sure would like to get a spec for these devices. Anyone know?

Q2) If I bought the aftermarket antenna meant to mount on the glass:
a) Could it be mounted in the rear facia area instead?
b) Would it's antenna connector be able to mate to the existing Radio Antenna Module wire or could a female-to-female adapter be used? (I suppose I could splice a coax but that is messing with analog RF)

I only took the back of the car apart once and forget how the connectors look. I'll have to check this weekend and verify what signals are and are not there.

Bottom line: Switch 5 volts to change bands, or install an aftermarket antenna, if it fits.

I do like AM for traffic stuff and right-wing crazy-nut talk radio, and also like FM when driving with my wife. I don't have to hear her say, "you listen to that crap?" Then we use Pandora too, but it uses up the data plan. And CDs work. But I want the radio too.

Thanks again for all the advice, schematics, etc.

(...imagine how it would be to explain to a future buyer of your fancy car, "Now this here little switch is for FM radio...")

markcz

Q1 -

Q2a - you could put it anywhere in the car that it fits

Q2b - no idea