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Jabiru LED landing lights.


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I took a spectrum analyser to my plane couple of days ago to see just hot much noise is getting in the radio. From the OSRAM 7W LED fitted to the strut with the fibreglass mount.

 

- there is some capacitive coupling from the lamp body into the strut.

- the majority goes out the leads and down the strut (we know) 

 

The noise floor was about -107dBm  with peaks to -97dBm every 500kHz that moved around with temperature and voltage.

Ideally, the radio needs to see a noise floor of less than -120dBm as not to become desensitized. 

There was also a bit of contribution by the EFIS

 

A single small RF choke clipped on the the wire reduced the interference by about 10dB, pretty good. 

 

There is limited space behind the lamp , , so I am going to make a replacement light socket- spade lug lead that has a high performance choke in it.

The first two I make, one will go to KiwiAviator. That's nail it. 

 

Ideally, you just run the DC up to the LED lamp and have the LED controller under the dash, but that requires wiring changes, so bugger that. 

 

-glen

 

 

 

 

 

lamp2.jpg

lamp1.jpg

lamp3.jpg

Edited by RFguy
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The LEDS are actually flashing and it's the circuit that does this that causes the interference. So, if you know the flash rate, build a simple PI filter to suit. Maybe a Spec analyzer picture with the led light off and a pic with the led on on would be good to compare the two. Something I might play with just to 'refresh' my fast fading electronics knowledge.

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yep, and since there is no concept of ground, you'll need a balanced PI filter. 

and you need capacitive input, because the internals will draw in pulses. 

Edited by RFguy
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