Someone recently asked me what kind of interface I use to key
FSK for my radio. Every time someone asks me this, I have to
dig in a drawer to find the schematic. So last night, with a bunch
of energy after working the P5, I decided to lay it out on my website.
A lot of people use opto-isolators, but I could never get one to
work. I suppose the ones I had in my junk box weren't good. So
I decided to try a simple NPN transistor circuit and it has worked
great on both of my computer/radios.
The circuit for FSK is identical to PTT & CW except for the DB 9
pinout.
If you are interested, the page is available off my RTTY page:
www.aa5au.com/rtty
or go directly to the interface page at www.aa5au.com/rttyinterface.
Hope this can help someone. Let me know if you have any questions.
These circuits should work with WriteLog or any other program that
requires FSK, PTT or CW from a serial COM port. What's nice is that
you can build all 3 circuits on a single COM port.
73, Don AA5AU
http://www.aa5au.com
http://www.geocities.com/writelog
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