ergodic

Just had a Kenwood DNX6990HD installed in my 2008 to replace the stock nav unit.

I drive this car all day for work and I use the FM radio on a couple of fringe-ish stations that hang out in the 88-90Mhz area, although they came in fine on the stock GM nav, as well as on my wife's Hyundai. But on this Kenwood, they're mostly static.

I have to believe the basic radio in the Kenwood is at least up to par with that Vietnam-war-era GM HU I had. The installer (I believe an excellent shop) has put put in an antenna booster which helped a little, but still not good.

Does anyone have any experience with this problem? Are there any impedance mismatch or grounding issues with the GM antenna going into the new head that have to be addressed?

As it is right now I can't live with it, but the Kenwood nav is SOOOOOO much better -- and the front/rear cameras a real help -- I really want to fix this if I can.

markcz

If you're still using the oem amp/speakers then they had to connect power to oem antenna module. Any chance you have aftermarket amps and they didn't?

I used an amplifier like this and it worked pretty good in my '07.

Many have reported good results with one like this, but that eliminates the oem antenna setup completely.

Plastic cars just don't make for good antennas. The oem radio can be tweeked by the engineers to make up for it, but aftermarkets are pretty much at the mercy of your antenna.

ergodic

Thanks.

No, everything stock w/ Bose. No aftermarket anything before this. The Kenwood radio does work fine on stronger stations so I have to assume the antenna unit has power.

I realized reading your post I've never actually known where the stock antenna is located -- I assume it's that "black brick" up under the rear-view mirror?

My installer wants to order up something else antenna-related and try it next week, so I'll wait and see how that goes. I don't care whose antenna it is as long as I can fix this problem.

Love the pic BTW

alretired

I installed the DNX 6990 HD in my 2006 also. I am having the same problem you are with FM reception. I have tried both the above suggestions to no avail. Please let us know the results of your installers new idea for antenna amplification.

markcz

In C6 the FM antenna is mounted on the rear vertical wall of the hatch/trunk, under the carpet/trim. It has two modules that get powered up when the radio is on. C6 also has a feedback signal from the antenna to radio, common belief is that it adjusts the gain somehow when the station signal is weak, but nobody really knows exactly how it works. Powering up the oem amp/speakers also puts power to the antenna modules.

The brick on the windshield is your onstar antenna. If you disable onstar you can pull it down pretty easily (DIY & pics here).

I assume you're talking about the avatar image, do you know where it's from?

ergodic

No idea on avatar.

It seems that to fix this I'm either going to need to replace the stock antenna unit, or find some bias voltage for whatever that feedback lead is to get the oem antenna gain up some - that seems unlikely if nobody's done it before.

So... any ideas on a really high-quality antenna to replace the GM one? Don't mind spending some coin on it. But everything I've seen looking around would be an external mount which isn't anything I'd want to do unless there's just no other option.

markcz

See what your installer comes up with. FYI, you can fit a normal sized external antenna inside the rear fascia

The avatar is a screen shot of the animated kid in the Def Leppard video for Let's Get Rocked

ergodic

The final solution to this problem turns out to be a little surprising. Hopefully it may be of help to others with this problem.

(This info is all from my installer BTW, I just got the car back and haven't looked at any of it yet myself.)

#1) Bypass the OEM antenna completely and install a powered aftermarket antenna. markcz: thanks much for the rear fascia suggestion; a clever idea and it seems to have worked out great.

#2) The cameras are the big issue. With power applied to either front or rear camera, reception signal on the Kenwood HD radio is significantly reduced.

The reason isn't clear, but it doesn't seem to be the cameras themselves. It isn't shielding, p/s or induced noise or any sort of static, it seems to be actually reduced signal or something in the ground plane that the cameras affect. Given this, I believe it quite likely is a design flaw in the DNX6990HD radio itself.

If anyone with a late model DNX and camera could verify this it would be interesting to know. It isn't hard to test - just tune a low-power or fringe FM station in the low FM band and then engage the rear camera.

Regardless, the solution is clear once you (or in my case your installer) figures out the problem. The rear camera is no issue as it only gets powered with the C6 in reverse. But the Kenwood apparently powers the front camera all the time; pressing the fascia button on the unit just engages the display.

So that front cam now has a separate power switch in series over by my left knee. This requires pressing two switches to get front camera, which makes it really too much trouble bother with. If I were doing this from the start again I'd opt to just skip installing that cam as I'll probably never use it this way.

And so if there's a better solution to this I'd really like to know - that camera would be really handy. A cracked lower radiator mount was one final motivation for doing this in the first place.

Anyway, with those two fixes the Kenwood FM radio is getting reception at about the same level as the GM OEM unit did, and I'm quite happy overall with the radio now.

Also my public thanks to Sam and AudioLab in Laguna Hills, CA. A great shop if you need an installer in Orange County.

alretired

Thanks for the update. That is some great info. I will be trying it. Do you know exactly which powered antenna he used and how he mounted it?

markcz

ergodic

The final antenna turns out to be just a standard non-powered, non-amplified car whip mounted in the rear fascia. Don't know the make so YMMV but overall there's absolutely nothing special about it.

I'm thinking about trying an in-line antenna booster just to see if I can goose up the reception a little more, which would be awesome if it works - I live in a canyon area where FM reception with anything is spotty.

The installer also put in an aftermarket GPS antenna under the front windshield all the way at the right. I'm not sure the reason for that as opposed to just using the OEM GPS antenna but he feels it's better.

HTH

joliett

The Corvette C6 has a very well designed antenna system within BOTH sides of the car.

Anyway, the rear antenna module's FM COMPOSITE SIGNAL (5 volts) no longer gets power when the STOCK radio is removed.

I installed a Kenwood DNX-8120.

I just put up a new post describing how to properly wire up the FM antennas. With GM Sevice Manual schematics and desciptions. Look here

I owe this forum a lot...

ergodic

Love to read it - what's the URL for the post, can't find it in a forum search...

joliett

CLICK HERE

McSweede

Came across this thread while googling similar issues with this head unit. I do not have a Corvette, mine is installed in an 08 Dodge Caliber SRT4. My radio reception was fine until one day all of a sudden I lost all but a hair of volume on AM radio. FM was fine. Had the radio replaced, its been fine a few weeks, this morning I turn it on, all AM and FM reception is down the toilet. I dont think its an issue with any car in particular, I think its a problem with this head unit. I'll be calling Kenwood today about it.

ergodic

My only question would be whether you have cameras installed? If so you might try disconnecting them to see what effect that has on RF reception. This was a real puzzle for a couple of days until we discovered - entirely by accident - that powering up either front or rear camera caused RF reception on the Kenwood to be seriously impaired.

Of course I don't know the first thing about the Dodge Caliber antenna system, but in general I'd check carefully for any grounding issues on the antenna since that is something that could change with a reinstall and would be a cause of poor reception, especially with AM.

Otherwise FM fine with AM bad is a mystery, unless the Dodge has some sort of dual antenna - you might well be right about it being the unit itself. Interested to hear what you find out.

McSweede

No cameras installed in my setup. On my drive home last night, initially the radio reception was OK, then out of nowhere I started getting all sorts of static on AM and the bad FM reception again. On AM it was sounding like there was lightning in the area, which there was not at all. When I got home, pulled the radio. I swapped the antenna adapter with another one I had on hand, as well as ran a new thick ground to part of the floorboard. Everything seemed OK this morning, so I will see how it goes in a few days. Far as I know there is nothing fancy about the stock antenna setup.

McSweede

Figured I would come back and post an update. After adding a new dedicated ground for my head unit, all my issues seem to have gone away. Guess this car just has a real crappy ground system. Hope I didn't just jinx that lol!

ergodic

Glad you got it sorted out! As I mentioned, a solid ground plane on a car is absolutely the most critical part of RF reception. Without it, no RF will work well. There's a good reason the ground wire is usually a very stiff hunk of copper.