LED_Fog_2

This second scope pic is detail of large pulse (or burst) from the first pic. This depicts 100kHZ repition rate (with higher frequencies that make this up).
Buck regulatore are run at a high frequency to reduce size of inductor (weight and cost) and will run at a higher efficiency (less loss compared to larger inductor) with cost being noise.
Look at Newark:
Linear Technology switching regulators. Study data sheet for reccomendations for filtering. Buy some and fool with. Reduce hash and radio will be happier.
Y9-02-22