Sattelite reception on VU machines

Just a quick question - would anyone know if there is a lower level of signal on these boxes? I have a moveable dish, and as it goes west signal does get a little weaker due to trees etc. Normally on my DB's down to 8-even 7 doesnt give much problem, and does occur under certain weather conditions, but while loading the satellites the other day it firmly resisted any on Thor with a signal level of between 8-9.[DB's were clearing OK]. Many thanks for any help. Brain

A lot depends on the image, you're using, but I have noticed my VU+ Duo2 sometimes refuses to scan channels in, when there's a lower signal quality, but once scanned in does show them.
I have also used the signal finder option, in Open Black Hole, sometimes works better than the manual scan option.