fm modulator question

I recently installed an fm modulator in a friend's car so she can plug in her ipod. it's one of those that has the little box that the antenna passes through, wired up with an on/off switch. When its on, the sound from the ipod is great, but of course the other stations come in horribly. When its off the reception is better, but still not as good as it was before I put the unit in. My question is if there is any way to fix that... My first instinct would be to find/make some sort of switch for the antenna cable, to make it completely bypass the modulator box, but I would assume cutting and modifying the cable like that would screw up reception just as much. Any other ideas?

The only way to fix it that I know if iis to not use it.  FM mods generally, err, suck.  What's the car and what kind of head unit, maybe there is a direct interface available.Support the12volt.com

its a honda with a not so good aftermarket stereo, no cd changer input, no aux in. I know they suck, I was actually surprised about the sound quality with this one though. live and learn, thats why I bought this one, to try it... Ive seen the ones that don't connect to the antenna and they suck much much more.