[1000mp] FSK interface using opto-isolators

[Pete Smith]

I tried an optoisolator interface for CW with my Mark 5, and found that the 
CW opto did not pull the key line low enough to trigger the semi-break-in 
-- I got CW sidetone but no actual RF.  No doubt this could have been 
solved by someone who knew what they were doing.  But there definitely is 
enough current to drive an ordinary optoisolator, at least in a desktop 
port, judging by my experience.

73, Pete

PS -- I have never had any problem with ground loops involving the serial 
or parallel port on my computer and my Mark 5, except for the sound card to 
microphone connection.  An isolation transformer solved the problem 
there.  And before anyone writes to ask why I didn't use a back panel audio 
input, I use the connection for stored voice messages in phone contests, 
and wanted to be able to route the audio through my SO2R box, along with PTT.

  At 06:30 PM 12/2/2004, you wrote:



>
>  Hi Group,
>
>Is it possible to use opto-isolators to generate both the Shift and PTT 
>using the computer serial Com port? If so, what would the value be for the 
>resistor be to operate the LED? More important, does the serial port have 
>enough current to drive an opto-isolator? I plan to operate RTTY using 
>FT1000 Mk5 Field and opto-isolators would completely eliminate any ground 
>loops.
>
>  Thank you,
>John V.
>
>
>
>
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