Looking to upgrade to an amp for my FT 847. Have my eyes on a Drake L4b. In researching before the purchase, I have been going over references on setup. The L4b needs 3 inputs from the Tx: AGC(ALC), VOX, Tx input. The FT847 has available ALC(AGC), Tx Output, but no VOX, although there is a VOX switch on the front. Any comments???