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LED running lights and VHF radio
I am the designer and mfg or the firststarled.com LED navigation and cabin lights.
Yes our lights are a Pulse Width Modulated (PWM) design, a variant I call a Variable Pulse Width (VPW) LED driver design, where the LEDs are turned off and on at a rate so that it appears to the eye they are on all the time but such that the pulses 'trick' the eye and look brighter than the average light intensity, thereby saving battery power.
The width of the pusles are a function of several things such as input voltage to the light and the LED arrays temperature and the lights ambient enviromental temperature and overcurrent conditions.
Regarding our lights and radio freq interference, a few of our first lights DID make some RFI, but that was almost ten years ago, designs from around nine years ago used a low pass filter to remove any generated RFI before it could get into nearby radio antennas and so RFI was not a problem with them after that.
Since six or seven years ago our designs use components that operate on different frequencies than before and so produce no RFI and these lights also use other internal components to prevent or block any RFI from getting into the light from outside, primarily by the means of an opticoupler/isolator between the PWM chip and the switching transistor.
The opto isolator is a component that in this case is spece'd so that it cannot pass RFI freq in either direction but can pass much lower freq signals.
Even though the microprocesser in our lights is in fact a PWM chip, its output is hundreds of thousands of times to low in freq. to make any RFI by itself and the chip only consumes about 2/1000th of an amp (2 ma) so even if radio freqs WERE produced by the IC chip they wouldn't go far (but they aren't in the first place) and the PWM waveform coming from the IC chip to the switching transistor is very clean and sharp with no harmonics, and that output signal goes through the opto isolator which would as mentioned block any RFI getting to or from the switching transistor in any case, and from the opto isolator to the gate of the transistor, a very short distance, the switching signal is 'buffered' to prevent any reasonences from being produced, and from the switching transistor to the LEDs at last, the waveform is very, very clean, there are no reasonences to make any RFI.
Great care has been taken to make sure there is NO radio freq interference.
You can hold the light as close as you want or even touching a radio antenna and tune the radio through any band you want and you will hear nothing.
The result is a light that is much more compact than others, fully sealed, tough, and about twice as efficient as the rest, for considerably less money!!!
I am about to introduce the MKIV version of the anchor light and it will make more light than earlier models as it uses the worlds most advanced LED as of this date.
If anybody wants more information on this subject I will be happy to help if I can, go to my website at firststarled.com and send me an email-Ken