Advice on cleaning up 5VDC from a wall-wart
The way to do this with the fewest parts - the only way to get 5Vdc from less than 5V - is to use a switching regulator. There are a few options, based on how much current you need. All of these can have inputs from ~1V-5.5V:


TI REG711: 1MHz; 40mVpp ripple; 50mA; regulation not listed.

Linear LTC1754: 600kHz; 65mVpp ripple; 50mA; 4% regulation.

Maxim MAX1759: 1.5MHz; 60mVpp ripple; 100mA; regulation not listed.

National LM2750: 1.7MHz; 4mVpp-15mVpp ripple; 120mA; 4% regulation.

Microchip MCP1252/1253: 650kHz/1MHz; 50mVpp ripple; 120mA; 2% regulation.



There are others that will give 140mA and more, but the linked RF widget doesn't need it, these were pretty cheap, simple because they're just charge pumps, take up little space and are entirely surface mount due to the high switch frequency. Those with MHz switch frequencies are less likely to interfere with your 315MHz-434MHz project.

Easiest way to do it, in my opinion, is to get a different wall-wart!