[pvrusb2] Problems Tuning Digital Channels on HVR-1950

[roccomoretti]

The install of my new HVR-1950 on an Ubuntu Intrepid box went with 
minimal hassle. Using the sysfs interface and 
channel-number-to-frequency conversions from Wikipedia 
(http://en.wikipedia.org/wiki/North_American_broadcast_television_frequencies), 
I was able to tune in the NTSC channels just fine, with /dev/video0 
giving good streaming.

The problem is that I can't seem to get the ATSC side of things to work. 
I tried following the directions at 
http://www.linuxtv.org/wiki/index.php/Testing_your_DVB_device, but 
(dvb)scan doesn't find any channels. (It will occasionally find one or 
two channels, but I can't get anything consistent.) It's not an antenna 
issue - I hooked the HVR-1950 up to a Windows box, and the Hauppauge 
software finds all of them no problem, with signal-to-noise ratios of 
20+ (some channels max out at 30). Trying to manually set the channels 
with the sysfs system doesn't seem to work, either, though I'm not sure 
if I'm doing it correctly for ATSC.

What procedure do you use to test the dtv side of the driver? Is there 
anyway I can tell if it's specifically a pvrusb2 issue, or if the 
problem is further up the chain in the V4L/DVB layer?

Thanks.