RF noise

While doing some AM/Shortwave DXing the other night, I noticed that my INOVA 24/7 was putting out RF noise! I'm betting that some of the inductors (transformers, coils, etc) in these switching power supplies aren't that well shielded.

chiphead
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Many newer lights do that and it is quite an issue with cave radios.

PeLu:

What's the latest hottest caving light these days??

Thanks /ubbthreads/images/graemlins/wink2.gif

I have had the same type of RFI when using my HF ham rig.
Thats why I now use a directly driven light.

Interesting - Now that I think of it - all the "electronic" lights should have to go for Part 15 testing, and have to be labeled.......

(BIG can of worms I just opened)

Ah... I had wondered if the red leds in the 24/7 were direct drive or not. And the answer is, no they are not. There is RF hash generated even with the red leds.

[ QUOTE ]
KC2IXE said:
Interesting - Now that I think of it - all the "electronic" lights should have to go for Part 15 testing, and have to be labeled.......

(BIG can of worms I just opened)

[/ QUOTE ]

Surefire does this - FCC/CE marks on the bezel.

Guys!

Some clarification here, my Inova 24/7 emmits this on the low beam. On the high beam end the frequency of the noise seems to double. No big deal mind you, just surprised.
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chiphead

I've got some caving plans in the works, but for right now I'm going to use my Inova 24/7 with its headband attachment.
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chiphead /ubbthreads/images/graemlins/smile.gif

[ QUOTE ]
sotto said:
PeLu:

What's the latest hottest caving light these days??

[/ QUOTE ]

A Petzl Aceto.

Here's another one. FCC/CE mark on an L2.

My L5 has FCC markings but it still causes RF interference.....

Two FCC classes, A and B (and technically a flashlight is exempt from both). A class A device can actually be pretty noisy. I don't remember the exact spread, but let me put it this way: You can generally achieve Class A with just good engineering practices, nothing exotic. Class B compliance has to be designed in from the outset, good engineering practices are nowhere near good enough. In some class B laptops I have worked on, I have been surprised at the number of shields and ground leads used internally to bottle up emissions. (Laptops sold in the USA must be Class B, desktops can be A or B depending upon the intended market).

FCC complaince does not guarantee RF silence, it places a limit on it, and the limit for class A is a lot higher than the limit for class B. I know from my trips out to the Test Range, that test eqipment had not trouble picking up the internal clocks at 10 meters with an omni-directional antenna, yet we were still about 3db inside the FCC class A limit on radiated emissions. My other experience is that most product that says it is class A, isn't (and that is from operating them on the test range). Class A is self certifying, and lets just say a lot of vendors take a very liberal view of the FCC regulations. Class B requires conformance, an conforming test report that the test range certifies, and the FCC issuing you an ID for the product. If your Class B product subsequently fails inspect, both you , and the Test range get fined. Suffices to say that the test range will insist that meet class B by a comfortable margin, so that any corners you may subsequently cut in manufacturing will still product a device that the FCC isn't going to fine anyone over.

[ QUOTE ]
mattheww50 said:
Two FCC classes, A and B (and technically a flashlight is exempt from both). A class A device can actually be pretty noisy. I don't remember the exact spread, but let me put it this way: You can generally achieve Class A with just good engineering practices, nothing exotic. Class B compliance has to be designed in from the outset, good engineering practices are nowhere near good enough. In some class B laptops I have worked on, I have been surprised at the number of shields and ground leads used internally to bottle up emissions. (Laptops sold in the USA must be Class B, desktops can be A or B depending upon the intended market).

FCC complaince does not guarantee RF silence, it places a limit on it, and the limit for class A is a lot higher than the limit for class B. I know from my trips out to the Test Range, that test eqipment had not trouble picking up the internal clocks at 10 meters with an omni-directional antenna, yet we were still about 3db inside the FCC class A limit on radiated emissions. My other experience is that most product that says it is class A, isn't (and that is from operating them on the test range). Class A is self certifying, and lets just say a lot of vendors take a very liberal view of the FCC regulations. Class B requires conformance, an conforming test report that the test range certifies, and the FCC issuing you an ID for the product. If your Class B product subsequently fails inspect, both you , and the Test range get fined. Suffices to say that the test range will insist that meet class B by a comfortable margin, so that any corners you may subsequently cut in manufacturing will still product a device that the FCC isn't going to fine anyone over.

[/ QUOTE ]

So would a resistored LED flashlight inherently meet class B, or would you expect the on/ off switch to be a factor ?

If it was battery powered, however diodes are inherently non-linear devices, so if you feed it with something other than DC, it can be a significant source of noise. In fact diode noise generators are common. in regulated lights, the DC to DC power supply is a significant noise source.

However this is largely academic. Flashlights are intended as mobile devices, so are exempt from the conducted/radiated emissions standards.