[RTTY] afsk to fsk

[Jerry Flanders]

Optos work. I have 3 in a homebrew copy of the usual circuit, one each for 
independent PTT+FSK+CW. Used with a FT-1000D. Don't know about the 4N25, 
though. I don't recall which ones I used. The 4N25 - 4N3x series seem to 
differ in "sensitivity" - if your 4N25 doesn't work, try one of the other 
ones. See if it works by monitoring how far it can pull down the FSK line. 
Typically, this is a TTL keying level.

Jerry W4UK

At 22:19 2/17/2005, you wrote:
>Hi, I am about to change over to FSK. My home brew interface I built for
>AFSK used transformers for isolation. I am a bit paranoid about isolation,
>this is a throwback to my working days! I know many use just a transistor to
>key the rig from the serial port.
>I would like to use an optoisolator like I have for the PTT. There was a
>posting recently that they wont work with the Ft1000. I have a Icom 756
>pro3. Is there anyone using an optoisolator for FSK using an Icom in the 756
>series. I have a 4N25 to hand. Thanks in advance, Pete G3KNU
>
>
>
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