The Model 6000 originally was assigned a 121.600 Mhz frequency. A retro fit to the new 121.775Mhz can be done at the factory. Also, for home made battery packs, we suggest a maximum of 8 volts for supply. A battery pack consisting of 5 alkaline "C" cells would supply 7.5 volts. Typical output signals from trainer units are of 150mw range at 7.5 volts supply. To achieve a simulated ELT with a broken antenna or low power, don't extend telescopic antenna or use 4 "D" cells to produce a 6 volt supply voltage.