Factory radio weirdness / poor antenna reception

[bond007]

I am trying to understand, once and for all, why my 1998 ti has poor radio reception. It has the "mid-level" stereo system: amplifier in the back left-hand side of the hatch, 6 speakers up front (one in the kick-panel, two in the doors) and 4 speakers in the back.

The stock BMW radio, according to the owners manual that came with the car (which conveniently enough, has a pin-out diagram) has two antenna connectors. One main connector and one labeled for diversity. However, the vehicle wiring harness for the radio, there is only an antenna connector for the main connector. I dug around and looked and I can't find one. What gives?

Could this be why the FM reception isn't so great? It will tune to a station manually but will not scan for stations or auto-tune. It also doesn't receive stations that it should be able to. The stock radio in my other cars will tune far away stations (60 miles or so) but the ti gets static when manually tuned to the same frequency.

The antenna base is indeed being powered. If I pull the power lead I lose reception and I get 12 VDC at the power connector. It sounds like it is working right.

Is the antenna base made to only work with a diversity system radio?

I ask this question, because I installed a Blaupunkt aftermarket head unit and it does the same thing as the stock radio in terms of reception. It doesn't scan/seek stations and reception is poor, last I recall. I put the stock radio back in because I prefer its controls and eventually to setup an MP3 input for it instead of toting around/burning MP3 CD's.

It sounds to me like the antenna base (which was replaced with a new one at significant cost since the antenna broke) is the wrong one for this particular car? Did BMW install the wrong radio parts in the car since the head unit expects diversity wiring yet there is no diversity wiring?

Any thoughts/comments appreciated.

[aceyx]

The diversity system is the antenna and the rear-window defroster (acting as an antenna). The junction is at the box in the rear left behind the carpet.

Maybe start there.

[bond007]

Which box are you referring to? I traced the antenna wire for a ways and didn't see it split. Elsewhere on here, I read that the diversity antennas were associated with the rear windows?

[Mallard]

Ahh Mr Bond..

[LostCause]

once again, your the man mallard!

[bond007]

Finally got around to further troubleshooting. Had to remove the hatch trim to unjam the latch (one of the last things that needs repair on my car). I found that the rear glass appears to have the leads for FM diversity but no wiring or amplifier and concluded that the issue must still be with the original antenna wiring.

I removed the antenna (non-amplified) from another vehicle I had and plugged it into the Blaupunkt. Lo and behold, the Blau is tuning all stations. While fidgeting with the head unit plugged back into the stock antenna lead, all of a sudden the reception improved. Apparently, there was a wiring fault in the antenna lead. I narrowed it down to the actual plug, which in trying to separate the plastic casing, the ground gave up.

Long story short:
I ran jumper wires from bare antenna wire to the radio and it works. Spliced in a new connector and I have full radio reception for either the Blau or the stock radio. I'll have to order a proper crimp connector at some point because antenna wire apparently only has like one/few tiny strands and I'm not too keen on the solder and careful splicing of the wires holding up.

Amazing how simple it was once I actually spent some time thinking about it and applying the process of elimination...