A fluorescent bulb is nothing more than a mercury vapor arc light. Once the arc is struck, the conduction of the mercury vapor inside the tube goes into a form of plasma that simply conducts a current sufficient to keep the plasma lit. That mercury vapor plasma (blue to ultraviolet) strikes the inside coating of the bulb causing it to fluoresce in any one of a myriad of colors -- from "cool" (mostly blue) light to "warm" (blue mixed with red) depending on the mixture of the coating. Note that the arc is struck at a relatively low voltage due to the nature of mercury vapor and the fact that the tube is a near perfect vacuum. The energy of the arc, due to its relatively low voltage, is rather minimal. (Note that the very old large fluorescent tubes such as the T-12 and larger required a much higher voltage to strike the arc, and they produced a fair amount of noise .... back in the "good old days" before we gave a damn about noise.) And, with enough care on the ballast design driving the newer tubes we could include noise filters to kill that noise before that noise was radiated with a very efficient antenna known as house wiring. To boot, that arc reverses itself 120 times a second, so you get little arcs at 120 times a second. FIlter if you will, but if the arc is strong enough you will get little spikes of energy way up into the VHF and UHF bands. Don't forget, you may be breaking volts with your arc, but your receiver is a million times more sensitive with ratings in the low microvolts for usable signal...quite enough to see that arc as "noise".
LEDs are inherently low voltage devices. As opposed to fluorescent and incandescent bulbs that are voltage driven, LEDs are current driven. If, for example, I have an LED bulb that required 20 milliamperes to light it up, and if you measured the voltage across the bulb you may come up with something that is around 1.5 volts. If you take a used flashlight battery with a nominal 1.5 volt rating but has deteriorated to 1.45 volts, the odds of that bulb giving ANY light is near zero. And if you take a fresh battery with 1.6 volts or so that bulb will be REALLY bright for about a millisecond before it melts into nothingness.
So, first of all, we are restricted to using current sources instead of voltage sources for the LED. That involves some electronics other than a simple transformer ballast. In the case of the fluorescent replacement, we have to have some way of dropping that 110 volts down to a reasonable number for the tube ... say down to about 20 volts or so for conduction AND we have to have some way of current limiting that voltage. The expensive way is with a fairly hefty power transformer and some electronics to chop that transformer output and input it to a current source. Inherent in "chopping" is a circuit known as a switching power supply, and now we aren't chopping a few volts but something 5 to 10 times larger ... and with efficiency being the goal, we "chop" at a relatively high frequency. High enough to spread the energy much further. Sure, we can put filters and all that but (a) it comes with a cost and (b) you can only filter so much. There have to be wires or conductors inside the switcher supply and they will have their own little antenna wire radiators.
Same problem with aircraft. Now instead of chopping 20 volts we only have to chop 12 volts. That cuts the required filtering down by about half, but it is still there. The nice thing (??) about aircraft is that we are less concerned about price than we are about performance. We can filter and shield the bejesus out our power supply and get that noise way down. Or we can buy our lights from China who could give a rat's hiney less about noise than price. Alternately, we can individually use the Chinese lights after a little internal "rework" do so some decent filtering. Just don't tell anybody you modified the "approved" product.
Your call. Did that help?
Jim
