A 6' dish will usually pick-up C-band signals from adjacent satellites located with 2 degree spacing. The reflector size is too small to be 2 degree compliant. This adjacent satellite interference can be worse if the FD is not properly set, causing stronger sidelobes. Proper FD setting will attenuate sidelobes and peak the target main lobe.
Optimizing the mainlobe on a specific transponder, which may or may not have overlapping signals from the adjacent satellite(s), will affect the performance on other transponders that may or may not have adjacent satellite interference. Tuning an undersized dish is best when averaging for best performance across multiple transponders and satellites.
Optimizing the mainlobe on a specific transponder, which may or may not have overlapping signals from the adjacent satellite(s), will affect the performance on other transponders that may or may not have adjacent satellite interference. Tuning an undersized dish is best when averaging for best performance across multiple transponders and satellites.