ChrisR wrote:

So how does all this techno babble answer the OP's question I wonder? :-)

Well, it doesn't directly. The OP *should* know by now however, that CN
and all his drivel should be studiously ignored. But, to be on-topic, I
would suggest the following:

1. If the 12V device draws minimal current, and/or is to be in use only
sporadically, then tap one battery and don't worry about it. If you're
using a couple of amp-hours per day, and recharge fairly frequently, the
diffential in the batteries will be, IMO, negligible.

2. If the 12V device (VHF IIRC) is a significant load, you can always
build a simple voltage divider (the VHF should be input voltage tolerant
enough to handle the voltage sag during transmission) and run from both
batteries. The overall battery draw will, of course, be somewhat larger
since you'll dissipate heat in the dropping resistor. If multiple
devices are used, however, this approach quickly becomes problematic.

Keith