REFLECTOR: DC power adaptor

[Dave Philipsen]

The proper way to effectively isolate the ground is by running the 12v 
from the airplane system through a voltage converter.  The converter 
basically changes the voltage to AC, runs it through a transformer 
(where it becomes isolated because there is an air gap with no physical 
connection between the primary and secondary coils), and then change it 
back to DC again.  Now you have 12v DC that is 'floating' in relation to 
the aircraft power.  Take a look at this link  
http://www.qcavionix.com/be-2aafl.php?cat=20505 under NEW: 3V FLOATING 
BATTERY ELIMINATOR!!  In my opinion, it's a little pricey for what it 
does but I'm pretty sure it will solve your problem.





John Dibble wrote:
> Dave, Andy,
>
> I'm looking into your suggestions.  I measured the current at 40 ma and calculate a
> resistance of around 12 ohms for 0.5V.
>
> FYI, the problem is that the headset doesn't cancel the low frequency noise and in fact
> amplifies it.  It's actually quieter if I take the headset off.
>
> If ground is the issue, is there a way to isolate the ground?
>
>
> John
>
>
> Dave Philipsen wrote:
>
>   
>> John,
>>
>> My guess is that the problem is not with the voltage.  Even though your
>> adapter is putting out 3.5 volts it probably isn't that far out of
>> tolerance for the headset.  A pair of new alkaline batteries may
>> actually present a voltage a little higher than 3 volts also.  I'm
>> thinking you may have a problem with isolation of the supply voltage.
>> The Zulu headset may not like the fact that the ground of your 3 volts
>> (3.5 volts) is at the same potential as the ground of your mike and
>> headphone plugs.  To test this out, simply power your Radio Shack
>> adapter with a 12 volt battery that is not tied in to your aircraft.  If
>> it works, then you'll know that the ground isolation is the problem.  In
>> fact, I saw an advertisement somewhere the other day in an aviation
>> magazine for an isolated ground power adapter for just this purpose.
>>
>> John Dibble wrote:
>>     
>>> I use a DC power adaptor from Radio Shack to power my Lightspeed 30 3G
>>> headset.  I recently upgraded to the Zulu headset and find it won't
>>> operate properly off the power adaptor.  The power adaptor puts out 3.5
>>> V which is higher than the 3.0 V on its selector switch.  Apparently the
>>> Zulu requires more precise voltage.  Is there an easy way I can reduce
>>> the voltage to 3V?
>>>
>>> John
>>>
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>> --
>> Dave Philipsen
>> Velocity STD-FG
>> N83DP
>>
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-- 
Dave Philipsen
Velocity STD-FG
N83DP