[CCarncross]

Depending on the settings you have for the picture output on your HR24, the AM21 should look identical to your tv's OTA picture.

The AM21 sends the signal to your HR24, whereas the local you get through D* might be being converted to MPEG4 and that may be where you are noticing the differences. I can assure you though that the HR24 is recording exactly what the AM21 sends it...

 

[CCarncross]

Yes, recordings from OTA take approximately 1.5 times the space because they are MPEG2 instead of D* mpeg4...and higher bandwidth in most cases depending on the number of sub-channels a station may use.