[RTTY] FSK, PTT & CW Interface

[Don Hill AA5AU]

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