So I was putting on my MPx shorty today and sure enough, I snapped the antenna base bracket off when I was trying to loosen the exterior part. Tried like hell, but it just wasn't meant to stay in one piece.

So my question is this...

I have the MPx shorty on there now. It's not leaking, looks fine, doesn't sway much. But the FM reception is terrible. Was the antenna base used as some sort of ground point for the antenna? Can I solder some wires to the part that was tack welded and run them to the base bracket screw points to restore signal?

I honestly don't care about the bracket not being there, so if a few wires would fix my reception, that's good enough for me.

 

I broke mine too. Mine broke at the threaded post though. Just order a new base. Its part # 15878187. Its $11.16 from GMpartsgiant.

The only thing is 05-06 cobalts had a 6mm mast thread. Gm doesnt make that base anymore. they only sell the 7mm base. maybe your MPx shorty came with adapters? if not, you could try a salvage yard?

 

Yeah mines an 05 so no go there. It really just seems like the base grounded the antenna and now that mine is gone its missing that ground. Might just take some wires out there and see if it helps.

 

Well the wires didn't make it crystal clear but they did improve it quite a bit. Might take a little bit of work but it's definitely a grounding point missing now that the bracket's gone. Don't know when I will have time to fuss with it again, but I'll post back if I can get a clear signal. I didn't exactly clean anything or grind down to bare metal so that could be the difference. Just pinned some primary wire to the side of the antenna base and wrapped it around one of the bracket bolts to test the idea.

 

The shorter antenna also makes it difficult for clean sound too. The signal needs to be strong with the shorter mast

Mine is an 05 too. I bought that new base but I also purchase a 7mm mast.

 

You can try adding in an induction coil. The antenna lengh determins it's resonance frequency. It needs to be either 1/2 or 1/4 of the wave lengh you are trying to recieve. The commercial broadcast FM is 88.1 Mhz to 107.9 Mhz. If using a shorter antenna, you need to tune it by adding a coil to basicly fool the antenna into apearing longer than it really is.
I don't know all the math so I cant tell you what size coil to use.