John Fleming wrote:
To repeat a previous message, I've had no problems with two - no, make
that three - different types of regular non-Darlington opto-isolators
keying the PTT, CW and FSK inputs of an MP. It would be very surprising
if the 920 required different levels, since all that generation of Yaesu
HF rigs are re-using a lot of the same circuit technology.
Ian, what "regular" optos did you use? I've heard of some successes, but
not with the 4N-series, e.g. the 4N25.
Devices that I either know personally, or know of, that have
successfully keyed various inputs of the MP from a PC's RS-232 ports
include:
CW :
4N33 (Darlington, CTR 500% @ 10mA) with 560R input resistor
4N36 (transistor, CTR 100% @ 10mA) with 470R input resistor
MCT5211 (transistor, CTR 110% @ 1mA) with 1k input resistor
FSK :
SFH618-A3 (transistor, CTR 100% @ 1mA) with 2.2k input resistor
TIL117 (no details handy) with 2.2k input resistor
CTR = current transfer ratio, which is the opto-isolator's version of
"gain".
The CW keying circuits are in G4AXX's and my own PC-MP interfaces, at:
http://www.granta.digital-crocus.com/equipment.php3
The opto FSK interfaces came straight out of the WriteLog Help files.
They are stuffed inside DB9 plugs... and please don't *ever* ask me to
open them up again...
G'night all.
--
73 from Ian G3SEK
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