Optima Colors: The Red Top are starting batteries, optimized for starting and not long discharge. The Blue Top are deep cycle (Marine/RV), optimized for deep discharge. The Yellow Top are somewhere in-between.
Because radio applications are often high current draw, like "starting", many go with the Yellow Tops for this application. But Blue would also work in many radio applications. Personally I hunt for data centers that are REQUIRED by their own rules to dump UPS batteries on a regular basis (battery replacement done by calendar date, often only two or three years old). Make friends with the right people, sign paperwork that the batteries won't end up being improperly disposed of (and a PR nightmare for the original owners) and haul away as many as you can carry in your vehicle without breaking the leaf springs. They're big, matched, and the manufacturers have OODLES of online care-and-feeding documents. Nate WY0X
