Thanks Terry, slight change, all converted B763 in the d/b are SF, F is used for manufacturers build freighters.
I should also note than these aircraft seem to flit between operations in the group as the flight ID,S used change between LCO, LNE, LAE on a weekly basis
Sure you need a filter. Please see cutout from your scan I have attached below.
A high gain antenna not only picks more ads-b signal, but also picks more out of band rf signals, which act as rf noise, and overload the dongle making it deaf to weaker signals from distant aircraft.