Radio emissions from SF L4/L5

I was showing off my L5 to a coleague at work next to my window,onto the snowy landscape below. I have a radio(FM) next to the window,when I turned the light on WOW -what a racket on the radio! /ubbthreads/images/graemlins/ooo.gif
I tried it the next day with my L4,and it was nearly as loud. I guess this is a good reason NOT to use them for security/police/sneaky beaky stuff.
Next time you're on the run at night,carry a radio with an earpiece.If the Man is using SF led stuff...
Could be a good video game in this,hmmm.
My ARC LS is silent by the way.Well done Peter! /ubbthreads/images/graemlins/smile.gif

I knew that lights with regulater circuits created RF noise, but I didn't know it created that much noise! Interesting...

How far away from the radio were the lights?

I wonder if this meets FCC requirements... I respect the engineering talents of the guys at Surefire, but RF hash is not something that you do not even think about in something as simple as a regular flashlight. The entire thing runs with a frequency of zero Hz. So they might have not even considered it.

How far away can you get away from the radio and still hear the noise?

Most non-critical electronic have to be desinged to accept rf interference, and not transmit their own as I understand it. I don't know that the SF would qualify as a rf elctronics device.

Any DC-DC converter or switching regulator is going to create RF because of the rich harmonics of the square waves generated by the circuit. Put an AM radio next to a computer, or for that matter a cauculator, then push some buttons on the calculator and listen to whata happens on the radio.

/ubbthreads/images/graemlins/huh.gif

Hello Phil B,

I have tested my L4 around several different radios, AM, FM, and VHF and have not heard any interference at all. I have noticed the computer interference. The flashlight should have better shielding.

Are you sure it wasn't your sparkling personality?

Tom

I wonder if that L5 is defective. Maybe someone could try it with a different L5.

The antenna for the radio points up the side of the window frame so the light would have been a foot or so away,but it was LOUD,I said it was LOU...oh forget it.
I didn't drift away with it but my guess is that it would reduce pretty quick.
Am I right to assume the current (or at least wattage) is an issue? The ARC has a Lux3 at 667ma,but not a 5 watter like the SFs.Or is the SF system "crude" compared with the ARC?
The radio is a cheap bit of cr@p and is not very sensitive even to stuff I DO want!
And Tom,the only sparkling I do,is pi55ing on the dumpster at 4am by torchlight.You smoothe talker you..

Paul R,I tried it with my L4 too.Same results,just slightly less noise????
It doesn't worry me,but it would be something to consider depending on your work and work environment.

A lot depends on the frequency of the station. My L6 has no effect on AM, and only slightly affects my PBS FM. But my inverter (converts 12VDC to 120VAC on my solar system) really freaks out some AM stations, but much less others.

Yes, *poorly* designed switchers will radiate *ALOT* of interference, I'm just amazed that the layout could have been done so bad to make decent RF emissions out of the front of the light.

I deal with this stuff all the time, and a proper switcher design and board layout will greatly reduce emissions. Unshielded inductors are a no-no.

It is funny to watch companies at the test labs, busy putting bandaids on their products to drop their emission levels. What is even more interesting, is they are just trying to pass the minimum FCC requirements for a consumer product, where we are testing for stringent FCC and FAA requirements for aircraft.

I wonder if the ARC4 has the same issues. BTW, just because a noisy light isn't picked up by one radio, doesn't mean it won't be picked up by another. The radio front ends have different methods and designs that cause sensitivity issues to things like adjacent channel interference, out of band interference etc.

My Arc AAA, CMG Ultra-G, and McLux/BB400 don't cause any obvious FM interference with a small portable radio (just tested, not extensively).

Just as a further thought on this,don't you Americans have a different type of FM/AM system to the UK?
It might not interfere with your radios(apart from slope detection perhaps).

[ QUOTE ]
Jarhead said:

I wonder if the ARC4 has the same issues. BTW, just because a noisy light isn't picked up by one radio, doesn't mean it won't be picked up by another. The radio front ends have different methods and designs that cause sensitivity issues to things like adjacent channel interference, out of band interference etc.

[/ QUOTE ]

What he said. /ubbthreads/images/graemlins/thumbsup.gif

EMI/RFI can be tricky. As stated above, sometimes the interference creeps in at the radio's antenna, but sometimes it can find it's way into an I.F. stage in the radio, or even right at the detector diode if it's not well shielded and/or it has long leads on it. And some "out-of band" interference can actually swamp the front end of the receiver, causing interference, even though the interfering frequency might be outside of the tuning range of the radio.
/ubbthreads/images/graemlins/icon15.gif

My L4 has an FCC certification mark on the head. My A2 has both FCC and CE certification marks on the body. So, I'd say it's safe to say SF considered the RF noise issue during the design/testing.

Cheers,
Bob

Ah, but what class/category did they pass?

CE certification means absolutely nothing. The CE requirement is that you have to live with whatever garbage you generate (TUV is another story).CE is entirely self certifying, you don't have prove to anyone you meet CE.

Technically the light is not subject to FCC emission controls. There is a general exemption for mobile devices.

Generally Class A compliance isn't all that difficult, class B is another story entirely. In as much as Surefire was no doubt considering it to be a commercial product, the worst case requirement would be class A, and class can actually be pretty noisy. For FCC A, you need to have a test report from an FCC certified testing range, and for class B, well let's just say the test report is the starting point.

At work I use a Sony Walkman radio and I noticed that if my L4 is in contact with my body, there is loud interference on the radio. None otherwise, and none with any other regulated light- A2, infinity, LS.

[ QUOTE ]
Phil_B said:
Just as a further thought on this,don't you Americans have a different type of FM/AM system to the UK?
It might not interfere with your radios(apart from slope detection perhaps).


[/ QUOTE ]

There is no such thing as a "different type" of AM/FM. There may be difference in frequency and with FM deviation. But if you change anything else, then AM is no longer AM and FM is no longer FM.

I have not been to Europe, but I understand that the AM band is different only is channel spacing. I think that FM is the same.


For what its worth, I held my Arc LSL-S next to a wide-band receiver (Kenwood TH-F6A) and tuned to receiver in 1Mhz increments from 1Mhz to over 200Mhz. I did not detect any interference at all.

I have access to a spectrum analyzer. Anybody want to loan me one of these long enough to grab an RF signature? I can post the results here and/or send them to Craig...