reduced number of channels

[maladmin]

Hi All,
Recently I repurposed an old laptop as a mythtv box, running mythtv on top of ubuntu (Saucy). The tuner is a Hauppage 950Q USB.
Everything is working great, except I have many less channels on the new system than I did using the tuner built into the TV.
I tried manually adding channels (WNED) and they occasionally work but more normally I can't get a lock. I assume the hauppage tuner is just less sensitive than the one in the TV?
If this is the case can anyone recommend a more sensitive tuner?
Thanks,
Tom