An excerpt from this site: http://www.wa0sxv.us/ci-v.html
Also of interest is the fact that, although they work, solutions
involving the Icom OPC-478 cable and variants which use two or three
transistors, use the serial interface power, and don't necessarily
generate a negative voltage may actually violate the RS232 signal
standards. As such, they may be vulnerable to numerous maladies
including lack of noise tolerance and possible rate and content related
errors. The MAX2xx line of chips actually include voltage doublers and
generators of negative voltage. Only one of the discrete component
designs I've seen actually does this. Compliance with these standards
can be measured with a voltmeter or examined visually using anRS232
signal display <http://www.wa0sxv.us/rs232board.html>. Another drawback
of the port-powered interfaces is that they simply may not work on many
laptops due to the lack of necessary control signals on the serial port.
73
Jim W7RY
On 1/15/2014 9:39 PM, Jim W7RY wrote:
Has anyone used the "transistor type" of serial to TTL (CI-V)
converter? Had any issues? I've built one with the MAX232 chip and
it works fine.
If anyone has had issues with a transistor type, please let me know.
73
Jim W7RY
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