Hello All, I have a requirement to install a battery backup system at a local ham repeater. It's a GE Mastr II running about 100 watts. With that much RF power, a couple of 100 AH batteries is only going to last a few hours.
My first thought was to add a second lower power RF amp (something like 20 watts or so) and use coax switches tied to the AC mains to switch to the smaller amp when the AC power was out. This should give me a factor of 4 or 5 more amount of time on the backup batteries. The second thought (and here is where I need input), was to bring the variable resistor (R8 on the VHF version) from the 10 watt driver board to a smaller external board. Then add a second variable resistor and a relay to switch between the two. This should give me two independent amp settings that can be controlled by a single control. Is there any reason why this should not work? It would save the cost of the second smaller amp and two fairly expensive coaxial relays. The relay could be controlled from the repeater controller or automatically with just a 12v DC wall wart. Dwayne Kincaid WD8OYG
