Radio emissions from SF L4/L5

[brightnorm]

[ QUOTE ]
Jarhead said:
...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...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...

[/ QUOTE ]

Should we be concerned with possible L4 interference when flying?

Brightnorm

 

[PhotonWrangler]

[ QUOTE ]
brightnorm said:
Should we be concerned with possible L4 interference when flying?


[/ QUOTE ]

Yikes. /ubbthreads/images/graemlins/ooo.gif
While the flashlight might not put out any more RFI than an average laptop computer, that RFI might be fairly broadband, and they DO tell you to turn off all RFI-emitting devices during takeoff and landing. Good question!

 

[brickbat]

[ QUOTE ]
mattheww50 said:

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.

[/ QUOTE ]

Where does this exemption show up in FCC rules? I've seen an exemption for devices used within transportation vehicles, but not a general exemption for all 'mobile' devices.

The FCC Class B limit is 10dB tighter than the Class A limit. I've designed many electronic products that meet the B limit. Based on my experience, an aluminum encased flashlight would not be a difficult design at all (from an EMI standpoint). - For one thing, it's entirely contained within a pretty decent Farady shield, and also it has no cables extending out of the housing.

Also, based on my experience, products that pass FCC Class B can and do interfere with nearby radios. Generally, they are not, however, going to interfere with your next-door neighbor's radio.

Jim

 

[Phil_B]

You're right of course Harrkev,that makes sense to me too. All I was saying is that I understood you had a different system,not just the spacings.
My ARC LS was silent too,I wondered if it was a different type of driver,or just the wattage is smaller and therefore less noisy in RF.
Photon wrangler,would Craig be "the LED Museum"?That might just prick up the ears of the SF people,especially with concern to Services/Forces sales.
I didn't say I was a radio engineer,just clueless and curious! Phil.

 

[PhotonWrangler]

[ QUOTE ]
Phil_B said:
Photon wrangler,would Craig be "the LED Museum"?That might just prick up the ears of the SF people,especially with concern to Services/Forces sales.

[/ QUOTE ]

10-4, Craig is indeed the curator of the LED Museum. And doing a damn fine job with it! /ubbthreads/images/graemlins/thumbsup.gif

 

[The_LED_Museum]

Thank you for your votes of confidence. /ubbthreads/images/graemlins/grin.gif

I just tried my L4 next to my $10 Countycomm shortwave radio, and tried all bands. There was some interference about an inch or two out on one of the subspace bands - er, I mean - shortwave bands, but nothing on any of the others, including AM and FM.

 

[brightnorm]

[ QUOTE ]
Telephony said:
Thank you for your votes of confidence. /ubbthreads/images/graemlins/grin.gif

I just tried my L4 next to my $10 Countycomm shortwave radio, and tried all bands. There was some interference about an inch or two out on one of the subspace bands - er, I mean - shortwave bands, but nothing on any of the others, including AM and FM.

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Does this suggest that its RF emissions are too weak to interfere with aircraft contols? This is a concern of mine.

Brightnorm

 

[PhotonWrangler]

[ QUOTE ]
brightnorm said:
[ QUOTE ]
Telephony said:
Thank you for your votes of confidence. /ubbthreads/images/graemlins/grin.gif

I just tried my L4 next to my $10 Countycomm shortwave radio, and tried all bands. There was some interference about an inch or two out on one of the subspace bands - er, I mean - shortwave bands, but nothing on any of the others, including AM and FM.

[/ QUOTE ]

Does this suggest that its RF emissions are too weak to interfere with aircraft contols? This is a concern of mine.

Brightnorm

[/ QUOTE ]
This could be a clue that could tell us whether the interference is coming in at RF, IF or some other means, which is going to vary by the design of the radio. I have a portable SW/MW/FM radio that has terrible susceptibility to interference in either the IF stages or the detector, I'm not sure which. It's easily wiped out by darned near anything that osacillates, regardless of the frequency. /ubbthreads/images/graemlins/icon15.gif

 

[Phil_B]

I never thought of aircraft controls Brightnorm.Good point.My main thoughts were to things like hospital equipment,and as mentioned,LEOs etc.
Phil.