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I have a high-power LED flashlight, 5 superbright leds in the element... it
is bright, if I bring it near an AM radios I lose all reception... this rfi is solely the product of the leds, the connecting wires and the batteries--the flashlight housing is aluminum... I have never checked just how large a bandwidth the rfi covers... Regards, John |
Yes, I would think there are MASERs in operation somewhere... they are
interesting devices--I don't think we have heard the last of them, by a long shot... The information you posted is interesting, I was not aware it was a Russian discovery, or discovered in the year I was born! Thanks for that bit of history... Regards, John |
Your flashlight likely has a DC-DC converter in it to keep the light
output relatively constant as the battery voltage drops. That would be the source of the RFI. It's also possible that the LEDs are multiplexed so that one won't hog all the current as they would if parallel connected. That also could create considerable RFI. Although the RFI is radiating from the components you mention, they aren't its source. Roy Lewallen, W7EL John Smith wrote: I have a high-power LED flashlight, 5 superbright leds in the element... it is bright, if I bring it near an AM radios I lose all reception... this rfi is solely the product of the leds, the connecting wires and the batteries--the flashlight housing is aluminum... I have never checked just how large a bandwidth the rfi covers... Regards, John |
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John Smith wrote:
"I have a high power LED flashlight. 5 superbright LED`s in the element...it is bright. If I bring it near an AM radio, I lose all reception." I have a Timex Indeglow watch with a fairly dim dial illumination when I depress the dialstem. It wipes out radio reception too. I suspect that solidstate diodes are noidy devices. They are efficient though as the light is not accompanied with much heat. As for diode noise, zeners are often used as noise generators, are they not? There are various ways to get an atom`s orbital electrons to move to a higher energy level. You can throw a stick on a fire or aim an electron beam on a CRT phospher.. From a laser, we`re looking for coherent radiation. Best regards, Richard Harrison, KB5WZI |
Well, you might be right at that (and contrary to how you took my posts--I
DO recognize you as an authority which has been around the block many more times than I), however, I have had that flashlight apart a half-dozen times, at least, it cannot be found! But, it is quite possible the current limiter is right on the chip with the LEDS and potted with it in the LED lenses... all five LEDS run in parallel.... Warmest regards, John |
I remember that "death ray" one!!!! I darn near died laughing when I seen
that--back then--and darn near died laughing again--just now--your reminding me of it!!! But then, I have a quirk, I am probably the only one... I have a VERY LOW respect for lawyers... grin Warmest regards, John |
There are various ways to get an atom`s orbital electrons to move to a
higher energy level... Your sentence, above, triggered some questions I have had in the back of my mind... In older lasers, they were referred to as "pumps", and indeed the light souce always seemed to be "strobed." I wonder if a LED is not "strobed", either occuring as a natural property of the LED itself, or circuitry incorporated on the LED chip, itself, which "strobes" it? Mainly, I have considered the above in regards to wondering about giant sheets of polished aluminum, focusing the sun on a laser rod (or gas tube) and beaming the energy down to the planet (as has been proposed by others), and if someway to "strobe" the lightsouce would have to be devised? And, this in regards to the "pump"-ing action I have heard referenced... as, if I understand it correctly, you must kick (pump) the electrons up a level, then let them oscillate back to their original state, then kick-pump them again... as the actual light is generated by the electrons shifting states, and NOT just the fact that they are at another energy level... It seemed to me the answer would be easy to find, from a search of the web... I was not successful... Your thoughts/knowledge? Regards, John |
Now, that got my attention. I haven't kept up well with LED technology,
but I haven't heard of any LEDs that have a built-in regulator, switching or otherwise. Out of curiosity, I tested the LED lights I have with an AM radio, and found the following: 1. A three-LED headlamp with no obvious electronics, fixed intensity, runs from 3 AAA cells: Quiet, no RFI. 2. Two different LED headlamps, one with 3 and the other 4 LEDs, with several intensity settings, run from 3 AAA cells: Loud audio whine. 3. Two small UV LED lights, run from 3 button cells: Quiet, no RFI. 4. Newly purchased one-LED flashlight, runs from a single AA cell: Generates an RF hiss. This is about what I expected. The #2 headlamps switch the lights on and off with varying duty cycle to get the different intensities. This can be seen by rapidly moving the light while on. The switching isn't visible at the maximum brightness setting but apparently the switcher is still on. It might be doubling as a regulator. High intensity LEDs seem to require about 4.5 volts for full brightness, and one cell is nowhere near enough to light one up without a DC-DC converter. So the #4 light has to have one. That explains its RFI. Built-in converters seem to be getting more common; without one, batteries last an incredible length of time, but at the expense of light intensity that falls dramatically as the battery discharges, especially during the first part of the discharge period. So unless there's some sort of LED defect that can cause RF noise, my money's still on your having some kind of converter or switch hidden in your flashlight somewhere. All the lights I have which don't have either are quiet. Roy Lewallen, W7EL John Smith wrote: Well, you might be right at that (and contrary to how you took my posts--I DO recognize you as an authority which has been around the block many more times than I), however, I have had that flashlight apart a half-dozen times, at least, it cannot be found! But, it is quite possible the current limiter is right on the chip with the LEDS and potted with it in the LED lenses... all five LEDS run in parallel.... Warmest regards, John |
John Smith wrote:
I have a high-power LED flashlight, 5 superbright leds in the element... it is bright, if I bring it near an AM radios I lose all reception... this rfi is solely the product of the leds, the connecting wires and the batteries--the flashlight housing is aluminum... I have never checked just how large a bandwidth the rfi covers... The LEDs may be pulsed by something resembling a square wave duty cycle thus generating a host of harmonics. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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