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Cell phone microphone as compared to aviation microphone

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scott(at)randolphs.net
Guest

Posted: Thu Jul 31, 2008 12:50 am Post subject: Cell phone microphone as compared to aviation microphone

Does anybody have a reference on what a cell phone headset plug expects in

terms of impedance and/or excitation signal levels?  And how this compares

to that produced by an aviation microphone?



I've wired a jack into my audio panel for plugging in my cell phone and it

"almost" works -- I can hear fine, but I have to yell in my aviation head

set's microphone to be heard at all by the recipient of my cell phone call

(and then only weakly).



Fine for checking voice mail before take off, but not so great for

requesting a clearance.



I suspect I need a preamp on the microphone line or perhaps an excitation

circuit to convert impedance to voltage but have been unsuccessful in

finding any data to help design the appropriate circuit.



Thanks!



Scott

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rv-9a-online(at)telus.net
Guest

Posted: Thu Jul 31, 2008 8:55 am Post subject: Cell phone microphone as compared to aviation microphone

Hi Scott.

Try this:



MICIN---||-----o----/\/\/\/----X----/\/\/\----GND

        0.1uF       100 Kohms            10 Kohm



Take the cellphone mic input from the "X"



This assumes that the MICIN signal from your headset is being biased by your

intercom.  The capacitor is critical to remove DC from the signal which

would overload your cellphone mic input otherwise.



 	  Quote: 	
		  From this, you'll see that the aircraft mic signal is being attenuated by

about 20 dB.  This can be varied by adjusting the ratio of the two
	


resistors.



Good Luck

Vern Little

Vx Aviation



www.vx-aviation.com

Audio Mixer/Stereo Headphone Interface/Tone Annunciator/Annunciator Lamp

Controller and more.



--

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