Re: [amsat-bb] Isolation transformer and 9600 baud.

["kc6uqh" <kc6uqh@xxxxxxx>]

This is a job for a led/ phototransistor And an op amp.
Art KC6UQH
----- Original Message ----- 
From: "John Magliacane" <kd2bd@yahoo.com>
To: <APBIDDLE@mailaps.org>
Cc: <amsat-bb@amsat.org>
Sent: Monday, February 20, 2006 11:54 AM
Subject: Re: [amsat-bb] Isolation transformer and 9600 baud.


> Hi Alan.
>
>> So, if a transformer isolation is not a viable option, could one use
>> capacitors on both sides of the data line to give protective isolation, 
>> and
>> still handle the signal properly?
>
> Maybe not.  If a high-voltage transient were to come along, it would pass 
> right
> through the capacitors for a long enough period of time to cause damage to 
> your
> soundcard.
>
>> Consumer sound cards have rather unknown
>> robustness.  Of course I have been operating a hardware TNC, tied to the
>> computer through the serial port, for years with no smoke.
>
> Same here.
>
> Just keep everything tied to a common ground, including the PC.  It might
> also help to power everything you wish to connect to your computer 
> (everything
> that uses a 3 prong power plug) from the same electrical circuit (or 
> common
> outlet strip).
>
> You might afford a measure of protection to your soundcard by connecting 
> to it
> through something like a 10k ohm resistor.  Then place a back-to-back 
> series
> pair of zener diodes (maybe 4.7 volts each) directly across the input.  In
> this manner, you'll prevent anything beyond about 5.4 volts from entering 
> the
> soundcard, regardless of polarity.
>
>
> 73, de John, KD2BD
>
>
> Visit John on the Web at:
>
> http://kd2bd.ham.org/
> .
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