Just installed new Focal 130K's and a Rockford amp in the back. Radio reception is now much worse than when I only had the headunit.
- Powercable run on the left side and signal on the right side
- Becker headunit
- Audi A4 Avant.

Any ideas?

it's available through any installer. It should cost about $10 bucks US.

Basically all it is is a 6" long by 1/2" diameter metal tube with a female antenna plug on one end, and a male antenna plug on the other... and also a power lead wire. Just plug the factory antenna into one end, and the plug the male antenna plug into your head unit... then connect the power lead wire to the "power antenna" wire coming off your aftermarket radio harness.

That should solve your problem.

Ok, but I don't see how that explains it all, since the reception was excellent before I installed an amp? I was using the same headunit before I installed the amp.

well, then you've stumped the band. I thought you swapped the head unit and amp at the same time, which would explain why that happens to most people here.... including myself.

Maybe there's some sort of electromagnetic interference happening with your amp.

sorry I can't help you with this

I will find out where the antenna cable runs and try to move my wiring around a bit and see if it makes any difference.

when you connect the antenna adaptor, don't forget to also connect the WHITE wire from the factory harness to it also...

Sounds interesting and I didn't know. Can you explain some more?

<center><img src="http://www.pbase.com/ruddyone/image/43874332/original.jpg"></center><p>I put in an Alpine HU and here's what I found out. Basically, hook the power antenna wire from the new head unit to the blue or red wire from the power antenna adapter. Then hook both of those to the blue wire from the wiring harness. To insure its the right wire, this should be plugged into the plugs which come from the car and it should be connecting the white wire from the car.

So, White wire from car connected to blue wire (via wiring harness) connect blue wire from harness, power antenna from head unit and wire from powered antenna adapter together.

Then connect the other antenna adapter parts to the car and head unit.

Here's a quick picture if that didn't make sense: