Got it working with just the 600:600 ohm audio transformer...
Jeff
----- Original Message -----
From: "Bill Coleman" <aa4lr at arrl.net>
To: <ku8e at bellsouth.netku8e@bellsouth.net>
Cc: <secc at contesting.com>
Sent: Saturday, November 18, 2006 8:49 AM
Subject: Re: [SECC] N1MM Sound Card Interface
>
> On Nov 14, 2006, at 10:48 PM, <ku8e at bellsouth.net>
> <ku8e at bellsouth.net> wrote:
>
>> I am using N1MM in the '1 - Single Card - One radio, No Sound Card
>> SO2R mode. I have a 1:1 isolation transformer from Radio Shack but
>> not sure how to hook it up. There is a red/black/yellow/white wire
>> coming out of the transformer. I think the mic is 600ohms input on
>> the radio. Any help/tips would be appreciated. Thanks.
>
> I built a similar interface so I can use my PowerBook or my Toshiba
> laptop on RTTY using CocoaModem or MMTTY (respectively).
>
> I have the headphone output of the laptop going to two 25 ohm 1/2
> watt resistors (one of each channel). I also bring the output off a
> to a 600:600 ohm transformer, through a 500 ohm potentiometer, wired
> as a variable resistor. (ie the variable arm is tied to one side) The
> other side of the transformer hooks to the microphone input.
>
> Adjust the output of the laptop carefully. There's usually plenty of
> signal and the microphone input is very sensitive. Be careful not to
> tie anything on the microphone side to ground, lest you suffer hum
> from ground loops.
>
> Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
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