Navy_Flier I see your Ultimate is the RTF version, just like mine! I also notice that your radio is a Futaba Field Force 7, of which I also own one (mine is T7UAP Super) updated to 2.4Ghz with an original Futaba S-FHSS 2.4Ghz module.
Please, read carefully "acdii" spot on explanation. In fact I would only add that if your module accepts pointing the antenna staright down to the floor, that is the best position. If not possible, straight up as suggested by "acdii" (but you must avoid flying overhead!) or folded to one side are the best options.
My comment on the BEC is not related to the power systems as BECs are offered aside electronic speed controls (many call them U-BECs) as a receiver/servos power system, so you may use a 2S Li-Fe or Li-Po pack as battery but the BEC powers with selectable 5,0 or 6,0 volts. Main problem is many, many such BECs are offered with very interesting current capabilities that, simply, they do nor met.
It is a very good idea to gain experience on the 2.4Ghz technology and capabilities with the old trainer and sincerely hope you decide repairing the Ultimate!