REFLECTOR: i pad / radio noise

[Don Johnston]

This has been a pretty active topic on the Cessna Pilots Assoc board. One
of the guys there is really knowledgeable electrically (I think he's got a
MS or PhD from MIT). So far, a "good" adapter for iPads is elusive. Seems
like every week someone finds a new one that looks promising but once it's
dissected, it turns out to have some issues.


On Sun, Sep 8, 2013 at 2:55 PM, Brian Michalk <michalk at awpi.com> wrote:

> Your best bet is to buy one with good recommendations.
> I like shopping at newegg, and when I can't determine reliability from
> specs, I'll go with highest ratings.  But it also has to be from many
> people.
>
> For example Product A has 5 stars from 10 people.
> Product B has four stars from 100 people.
>
> I go with product B, because the five people could be paid shills.
>
> On 09/08/2013 02:17 PM, John Dibble wrote:
>
>> On 9/8/2013 12:04 PM, Brian Michalk wrote:
>>
>>> 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.
>>>
>>
>> Would a more expensive adapter work better?  Or a certain brand?
>>
>> Thanks,
>>
>> John
>>
>>>   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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