PRC344 low battery warning v.1.0 - 1st working

After a lot of fiddly work with these tiny 0603 sized SMT parts, and the retrofit of a standard 1/4w resistor to effect the required virtual ground, I now have the very first of the version 1.0 boards installed and tested in my PRC344.

Fiddly work - those black specks are the resistors!

The chosen resistors for Ra and Rb actually, in use, give an alarm threshold of 20.86v. Thats a little higher than I was aiming for, but not bad for fixed value 5% components.

Completed board

Insulated inside heat-shrink ready to install

The radio is now back together, tested on the variable bench PSU, and now sat monitoring North-East ICF on 270.050MHz, where there is some activity. Rather annoyingly, there is a dreadful sproggie from my PC right on that very frequency! So I have to move the radio quite a way clear of the computer.

I now need to let the radio drain down the battery until the alarm starts, and then check the battery voltage and the alarm function.