REFLECTOR: i pad / radio noise

[Brian Michalk]

I had a power adapter screw with my car.  I bought another one, and the 
problem went away.

When I build my circuit boards, the biggest noise problem I have is when 
a voltage regulator oscillates.  It either needs more capacitance, or a 
lower resistance (ESR) capacitor to prevent the oscillation.

I suggest getting a new power adapter.  If that is not an option, take 
it apart and add some ceramic caps to any caps that already exist.  Kind 
of difficult if you don't have an oscilloscope.

No, shielding the cord most likely won't help.  I'll bet it's noise 
injected into the power lines in the form of voltage spikes.  It's not a 
radiation problem like magnetic or RF.

On 09/08/2013 08:13 AM, John Dibble wrote:
> I now understand why there is concern with the use of personal 
> electronics on commercial aircraft.  Previously I reported erratic 
> radio noise.  It was the same noise as I get when I pull the volume 
> knob to receive weak signals.  Also my nav was not picking up VORs 
> very well.  After a long discussion with an avionics technician I 
> decided to investigate my i pad.  He said that because it's not 
> shielded, it can interfere.  I had a hard time believing that because 
> many are using the i pad and no one else is complaining. However, I'm 
> using a power adapter and he said that can be a problem also.  So I 
> tried unplugging the power adapter and, sure enough, the radio noise 
> went away.  Also the nav came alive and picked up VORs like it 
> should.  I also found that if I turned off the alternator, I could 
> leave the power adapter plugged in and the radio noise was gone.  This 
> did not eliminate the nav problem, however.  So now I'm turning to the 
> electronics wizards in the group to see if there is any way I can have 
> my power adapter and use it too.  Would insulation around the power 
> cord help?
>
> Thanks,
>
> John
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