There is a parameter you can put into the Dvico Fusion HDTV 4 driver using /etc/modprobe.d/options
options dvb_usb_dib0700 force_lna_activation=1
I don't know if it actually does anything. Haven't tried it with/without to compare (would use tzap to try it out).
Does anyone else have the Dvido Fusion 4 working OK? Mine just keeps failing randomly. Tuners go offline, or they are not detected at bootup. I am suspecting a USB driver problem. Maybe the dreaded "USB disconnect". This is an AMD board with 680 chipset.
I would second the vote to "put in a masthead amplifier". Notice that I get dropouts on the computer that just don't happen on the TV.