In an installation with SAT92 receivers, some of the modules are not tuned in. Why?
Older units do not have PLL tuners as they do nowadays.
The default adjustments do not necessarily coincide with those that already exist in the installation (the TV SAT channel IF frequency does not coincide 100% in two identical LNBs).
This is why the best way to tune the input channels is onsite.
First you must disable the AFC, and then tune in the desired channel until the best possible image is achieved.
Finally enable the AFC again.