ericdwong

....My FM reception really really sux on my coup, even with an aftermarket radio. The reception in my 97 Maxima (which has diversity reception- 1 power mast style antenna, and one in the rear glass style) has the best reception for a car radio I've ever seen. Anyway, it does not help my front antenna was rubbed off, probably cause there used to be a tint strip there and that was taken off. I repaired that the best I could with circuit board repair conductive paint. However, the reception still leaves to be desired.

I am thinking about putting in a power antenna on the rear fender from a 03 vert. I cannot get ANY AM stations whatesover and most FM is rather fuzzy. now that I'm on the highway alot, I need to depend on the AM and FM to check traffic (and I cant stand it when I know that something is wrong with my car).

Or, is there a way to check that my current diversity reception is functional right now? I know theres a box up in the "hoop" that goes over the antenna.

bbvett

Not sure where to start with this but I'll give it a try. Ok I think you have an aftermarket HU. So I will address it that way. In the Coupes there are as you know antennas in the windshield and hatch glass. There are 2 other parts to the system. One acts as a connector for the rear hatch ant. its at the top of the roll bar. The other is on the drivers side just above the seat belt retractor, this is where both antennas meet and get chosen then go by a single ant. wire back to the radio. The problem is this the connections at this unit are power, data and ground. Ground being supplied by the mounting bolts. The factory head unit sends data in some form to this unit with regard to signal strength after market head units don't do that. I don't know what happens when this unit does not receive a data signal but signal strength suffers. Some people have said to try grounding this data lead other say put +12volts to it. I don't think it's that simple.
I currently have the same situation and ordered the power antenna for mine. A few vendors are selling kits for upgrading FRC fixed antennas to power for $150-$200 which will work but you don't get all the parts needed if you don't have the fixed antenna. There is an aluminum plate that acts as a ground plane that's not included also some grounding studs for the ground braids that come off the antenna that are not included. I ordered all the parts from Fitchner Chevy the guys there are really great and give discounts to Corvette Forum members. Hope this helps, Bob

ericdwong

Good stuff! Damn the bose system! Ill have to take a look, I knew it had somethin to do with that damn box. Maybe there is a way to bypass that box. I dont know much about the no-ground plane antennas though.

Good info on the other stuff as well, about adding the antenna from a FRC/vert. I love this forum!

bbvett

The ground plane thing is simple if you install the power antenna without the aluminum plate installed and grounded to the frame below the antenna you will get poor reception with the power antenna also. Bob

ericdwong

OK I pulled the panels to have a closer look. At the switcher 'box' thats low on the B pillar. Interesting the 2 inputs on the box use the standard motorola style antenna plugs that all other 'normal' cars use, then the output side uses the GM mini style. I crudely played around with it by plugging in various combinations of the inputs. I think the switching mechanism still works, but it doesnt work well since theres no 'direction' from the OE head unit. I plan on getting just a standard antenna extension cord and plugging it directly into the radio to bypass the combiner box altogether.

I gotta research more on diversity reception for radios... that would be awesome if I'd be able to utilize a true diversity system on an aftermarket head.

I've found this http://www.delphi.com/pdf/d/ces_DD03E0931.pdf interesting, as Delphi does make the 'fuba' diversity system. I wonder if I can talk to one of their EEs or techs there to get some more info.


[Modified by eRiCdWoNg, 12:44 AM 2/11/2004]

bbvett

I checked out the pdf looks like its geared toward OEM's. Perhaps they make the one in the Coupe so a phone call might be worth while. I still can't see how it could be adapted to an aftermarket HU though, since there is no data output from the aftermarket HU. Mean while I going ahead with the electric antenna. I should have all the parts by Friday. Bob

ericdwong

Im gonna try the direct to the rear or front antenna first. If the reception still sux then I may try the power antenna.

I didnt test the box cause i wasnt about to pop in the oe radio but I found on the usenet about somebody else who made some observations about the wires goin to the box, and one of them gets 12 volts whenvever the radio is on and the other gets 7.5 or so when it is in FM mode, but 0 in AM. Hmm....perhaps this is the reason that on my OEM radio when i turn on the defroster, the reception on FM sounded like somebody pulled the antenna out.


[Modified by eRiCdWoNg, 1:01 PM 2/11/2004]

bbvett

That's an interesting find if it's true Eric. Seems as if you take the power antenna lead from your HU and supply that +12 volts to the module and then using a resister supply +7.5 volts to the other terminal your antenna would atleast be tuned for FM reception. With no voltage the default seems to be for AM.
Perhaps there is an intergrated amp in this module also. Maybe it's not a diversity system at all. The module may just amplify and select the proper antenna (front or back, AM or FM) based on wether there is 7.5 volts present.

The dark green wire would be hooked up from your power antenna output.
The pink wire would be the one you would use a resister on to drop the voltage to 7.5.
Let me know if you decide to try this and how you made out. Bob

SlumpinC5

I would like to know more too. As when I swapped to an aftermarket deck in my Coupe my reception dropped off. Still works but not as good. If anyone has any details please let me know. I might try the 7.5V and see how that works....

knewblewkorvette

ttt
:lurk:

ericdwong

Anybody with a coupe who still has the OE radio who's into electronics want to test this out? I think the red gets 12 volts whenever the radio is on, and the green is only on when FM is on, and it apparently gets 7.5 volts or so. This may or may not be data, not sure, or it may be DC just running thru a resister. If I get a chance Ill try to call Delphi.

I wonder that when the radio is in AM mode, and no voltage is going to that green wire, if the unit switches to "use both antennas" mode. This may be OK for AM, but for FM its a no no- as it would cause cancellation for having 2 antennas paralleled like that. Hmm.


BTW, the verts and FRC/z06's, do they still have diversity? Only using the front antenna and the whip antenna rather then the 2 in the glass ones like the coupe?


[Modified by eRiCdWoNg, 11:50 AM 2/12/2004]

bbvett

Eric, in my previous post I wrote the GREEN is the +12 volt and the PINK is the data this is the one you said would be the 7.5 volt FM
This is from the shop manual. Bob

ericdwong

Oops, didnt read carefully. Anyway, in the shop manual, does it specifically say "data"?

OK I went outside and played around with different combinations. This is ODD, now I'm even more confused as to which setup to use. These are the various setups I've tried:

- like I had before, GM mini to standard plug on receiver end, box on the other end.. but NO 12 volts to green. I've had varied results here. It seems some of the times it got good reception, and other times it did not. AM reception (important for me, I'm on the highway 4 days a week) was non-existant.

-similar to above, but 12 volts applied to green. AM was definately improved. However FM was interesting. 99.1 mhz was WORSE with the 12 volts then without.

-rear antenna directly connected to head unit via extension cable: AM worked pretty good to pick up the strong local station (night time too, mind u). FM, the lower end of the spectrum was received horribly. Upper FM seemed to be good.

-front antenna directly connected to head unit. AM and lower FM was good. Upper FM seemed to be OK, so so far this seems to be the best combination so far.

Ill go measure the 2 antennas, perhaps they are differnet lengths for the different parts of the spectrum.

Conclusions: Well I dont really have any yet I gotta do some more testing actually driving around, over several days with different atmospheric conditions,. Tthat "data" jack we gotta figure out if theres a way we can utilize the diversity.

I'd say I'll probably connect the power antenna wlre lead of the aftermarket HU to the green and try it out for a few days. Then maybe try it out with one of the other few combinations.


[Modified by eRiCdWoNg, 11:27 PM 2/12/2004]

bbvett

Eric, from the shop manual (pink) "Radio-on signal".

The dark green wire is "antenna relay coil supply voltage"

Now the green wire is also used in the convertible for the antenna up and down relay located inside the antenna. But the pink is not used.

ericdwong

Interesting. Maybe all the switching happens inside of that box. I'm a little scared to apply 12 volts to that pink wire, so maybe i'll pass it thru the resistor. The only reason I think it may be 7.5 volts or so is cause of what I read on the newsgroups. However, if that is just the 'radio turn on' lead, then maybe it is easier then we think.

I almost wonder if those secondary boxes (like the one in the hoop above my head) need the power from the main box to function properly. Like a remote antenna

I did some more testing out on the road tonite- front antenna definately better for lower and AM signals. rear antenna- better for upper FM.

Hopefully all this speculation can end with a call to delphi. Ill try that tomorow and hopefully I speak to someone who knows what they're talkin about.

bbvett

I'll tell you what Eric If you blow your module out you can have mine. Hows that? Bob

knewblewkorvette

:lurk:
as long as you guys figure out this problem before April I'll be happy. Good luck :cheers: :lurk:

SlumpinC5

Definetly let us know what you find man! Very interested, would be nice to get perfect reception with the aftermarket deck.

DNAST1

ttt

knewblewkorvette

:iagree: ttt