FM Static

[sonerick]

Power to that wah? The huh?

Look, i dont know if this helps, but this is how i handled my 1-to-2 antenna problem (thanks to Krup).

I bought the 2-to-1 harness from Amazon plus the adapter that solves the 2-different-size-male-ends on the antenna inputs.

I havent had a problem with static at all, AND i get Boston radio stations all the way in Palmer, MA. on the Mass Pike!

I installed a Scion HU, both with and without the adapters you show in the pic above. Reception was worse with the adapters, so I took them out. I have them lying around if anyone wants them.

On some aftermarket head units (e.g. not Toyota/Scion), you have to provide power to the antenna lead on the aftermarket wiring harness. This will solve the FM reception issue. Here's a post from someone who did this fix:

Not sure if this will work with your Pioneer NAV HU or not, but I found a VERY easy solution to the diversity antenna issue with my new Kenwood NAV HU. All I did was connect the regular antenna connection from the 4Runner to the Kenwood, tape up the secondary smaller antenna connection coming from the 4Runner with electrical tape, then I crimped the blue "power antenna" wire from the wiring harness to the matching blue power antenna wire on the Kenwood cabling. On my kenwood cables it was clearly labeled as such and the packaging that came with my wiring harness also labeled the blue wire as the one for a power antenna. I originally did not connect these wires as I thought they were meant for vehicles that have a true power antenna that goes up and down from the hood, but I guess this cable also supplies the extra power boost needed for our diversity antennas in our rear drivers side windows. Good luck dude!

Besides, the OP already stated that he used the adapters and they didn't do anything for him.