OK,
I hooked up a Radar Dispaly to my circuit. I have now determined that I need to create the video output level at the 5000us rate, but I have the liberty of updating as I update the antenna syncro angle (since it holds it last scan value). That way I can update at the end of each 180 scan. With the PIC18F4520 clocked upto 16 MHz it seems to work pretty fast when receiving new data with a RS-232 u1pdate rate of 38400.