Power to Radio
Hi,
I just use a 12v DC battery purchased from any hobby shop for $20 and a charger for it @ $10 from the same type of shop.
Then go to Dick Smiths and buy some red and black cable, a power plug that goes into the side of your radio, a 1 amp fuse and fuse holder and a on/off switch plus some electrical conector terminals with crimper (unless you know someone with these already) - they aren't expensive.
Then just wire red cable from +ve terminal of battery to fuse holder, then from fuse to switch, then from switch to power plug (for radio) and with black cable from power plug back to -ve terminal of battery. Also it would be good to add an earth from -ve terminal of battery to airframe.
This way you shouldn't experience any dangers of spikes etc as the battery is completely isolated from the main charging circuit of the magneto.
It would also lessen the chances of interference also.
These solid black hand size batteries last hours and hours per charge running my radio, intercom and headsets etc.
Azhar