I have a Necvox dual diversity freeview box installed in my car with two internal window mounted amplified aerials, but the signal is terrible.

The setup replaced one of these cheap single aerial freeview boxes I bought off Ebay but the signal was actually better on the cheap box.

Question is, in certain areas I get a

"no signal" message on the TV screen but if I touch the window mounted aerial with the tip of my finger the signal improves dramatically and I get a perfect picture.

Anything I can do to improve the signal without touching the aerial all the time?