A C182RG pilot suffered the intermittent loss of all navigation and communications systems.

Narrative

On a routine flight; I experienced problems with the avionics in my Cessna 182M. Both my GNS403W GPS/NAV/Communication and my King KLX130 GPS/Communication began cutting in and out as did my transponder. Added to the problem; both communications began an oscillating background noise that increased in intensity until all communication was drowned out. At this time; I was still on Departure Control and about to switch to Center. Fearing damage to my avionics and the possibility of electrical fire; I turned off all electric power and went to my battery powered GPS III Pilot and my ICOM radio; which is equipped to plug into the external antennae; and with receptacles for my headset. Following the aviate; navigate; communicate sequence; I had no trouble keeping the aircraft level and reasonably straight as we were in VMC. I turned the GPS on first; and then; while it was warming up and getting a position; I got the hand held ICOM out of the glove box; and hooked it into the external antennae receptacles and my headset. The ICOM was completely dead. At that point; I removed the battery pack from the ICOM; and began removing and replacing the ten AA batteries with one hand while I flew the plane with the other - no easy task. I only had eight fresh batteries and after replacing those; I tried the ICOM again. It was still dead. Later testing showed that there was still one completely dead battery; which kept the other from powering up the ICOM. At that point; I gave up on communicating and turned my attention pack to navigating. Checking the compass; I realized that I had let the heading drift a full 90 degrees from northwest to southwest. Checking the GPS; there was nothing on it except the message page saying 'you are in a restricted area.' Having little idea exactly were I was; not being as familiar as I should have been with the portable GPS operation; and having let my preoccupation with the ICOM radio; divert my attention from navigating. I decided it was time to declare an emergency and ask for help. I turned the electrical power back on; and discovered that I could communicate for fifteen seconds or so before both sending and receiving was interrupted. I first called Center on 121.5; declared an emergency; and asked for a vector to the nearest airfield. Then the radio failed again. On my second attempt an airline flight relayed a message from Center telling me to contact them on their regular frequency for that area. On my third attempt; I did reach Center; and asked again for nearest airfield and vector. They provided me with a vector back to my departure; and I took up that heading. Each of these communications lasted about fifteen seconds before I had to turn the power off again. Once settled on a course back to ZZZ; I turned my attention back to the GPS; and entered a 'Direct To' ZZZ command. After that; things settled down. I turned the electrical on again long enough to announce that I would do a straight-in approach to Runway 17 at ZZZ; without further communication. Approach acknowledged and gave me permission to land without communication. I landed without further problems and was met by two crash trucks; etc. As there was never an electrical fire; once I was on the ground; the emergency was over. I still don't know if I was ever actually in a restricted area. Lessons learned; back-up equipment is only as good as your familiarity with it; and all battery powered equipment should be checked before every flight. Also; the aviate/navigate/communicate rule only works if you don't allow yourself to get bogged down in one of the three to the exclusion of the other two.