[RTTY] Using a 4-conductor laptop audio jack to decode RTTY

[Joe Subich, W4TV]

The preamp in an electret mic typically draws 1 mA (e.g. 4.7K resistor
in series with a 5V source) or less.  I'd start with something between
4.7K and 10 K depending on what you have in your junk box.

73,

    ... Joe, W4TV


On 10/30/2017 3:46 PM, Dennis wrote:
> I have a laptop that uses a 4-conductor jack for audio.  I have the correct
> adapter, but I can't get it to decode an audio stream.  Even though I have
> the correct adapter (I know because an electret microphone works FB
> when I connect it to the adapter jack), when I connect the audio cable
> from the radio the laptop reacts like there is nothing plugged in to the 
> jack.
> 
>  From memory, it seems to me that the way to solve this is to use a 
> resistor
> across the microphone line so that there is some current drawn thru the
> mike line, because the laptop uses that current draw to signal that a mike
> has been plugged into the laptop, but I can't find any references on the
> web.  Can someone help me out with this?
> 
> Thanks.
> 
> Dennis W1UE
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