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Re: Isolation transformer and 9600 baud.



Hi All,
Yes the compensation can be tricky ,but if yuo use a VCO ( 74HC 4046 and 
another in a phaselocked loop configuration for receive and use the opto to 
send the frequency accross using a center frequency of a few MHz you won't 
need compensation. You can also use PWM and recover it in a cap. Even better 
yet differentiate each transition, use a  pulse transformer, and integrate 
the pulses. All you need is to accurately know the transition times. DC 
coupling is necessary only because of baseline shift. If each transition has 
an equal amount of energy and the coupling time constant is shorter than the 
minium transition to transition time ( 2X baud rate) you can AC couple the 
signal.using integration as each pulse is in the opposite direction.

Art ,
KC6UQH
----- Original Message ----- 
From: "Bruce Bostwick" <lihan161051@sbcglobal.net>
To: <amsat-bb@amsat.org>
Sent: Tuesday, February 21, 2006 5:56 AM
Subject: Re: [amsat-bb] Isolation transformer and 9600 baud.


Optoisolators are kind of troublesome in their own ways, primarily
irritating nonlinearities.  This isn't too hard to fix, but does
require a second channel through the optoisolator in the op amp's
feedback loop (or a second opto as close as possible to identical
with the first one) for deemphasis.  You might be able to linearize
the output with a compensating circuit in place of the opto but it
wouldn't be trivial.

On Feb 21, 2006, at 1:07 AM, kc6uqh wrote:

> This is a job for a led/ phototransistor And an op amp.

"Correct morality can only be derived from what man is-not from what
do-gooders and well-meaning Aunt Nellies would like him to be."  --
Robert A. Heinlein

[demime 1.01d removed an attachment of type application/pkcs7-signature 
which had a name of smime.p7s]
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