[RTTY] FSK and Dell PC with TS2000

Kok Chen chen at mac.com
Sat Jul 10 13:52:49 PDT 2010

On Jul 10, 2010, at 6:50 AM, Marc Tessier - VE3TES wrote:

> Until windows boots up all is normal, then once the serial port initializes, I get a PTT lock up on my TS2000, my interface is the one shown for FSK on Dons AA5AU RTTY setup page.

On some operating systems, depending on the serial port driver, the state of the RTS and DTR lines of an unopened serial port can be either asserted or unasserted.  It is only after the program that controls the serial port starts running, and has opened the serial port, that you finally have control the RTS or DTR into the state that you want it to be in.

If your computer leaves the RTS of your unopened serial port asserted, short of rewriting the serial port driver yourself, you should be able to add an inverter to your interface box (whats another 2N2222 ? HI HI).  And then tell the software that controls the PTT to invert the RTS logic.

This happens all the time, and is the reason that I had included an "Active High/Active Low" selection in a piece of software for Mac OS X called cocoaPTT (you can see the PTT selection in the second diagram on this page http://homepage.mac.com/chen/w7ay/cocoaPTT%202.0/index.html ).

IMHO, the surest way to control PTT on a rig is to send the rig the proper CAT commands.  I have the option to do this, I would recommend it over using an RS-232 control line.  Next best thing (again IMHO), is to use one of the commercial interface boxes which you have to send a command string to (not RTS) to turn PTT on or off.  

In either of these two cases, you won't have to worry about uncontrolled transmissions before every piece of the PTT command chain has "booted up" and is running.  

One of the commercial boxes that I use even has a watchdog timer that disables PTT if you stop sending it a periodic "stay alive" signal -- so if your computer crashes, the PTT will turn off by itself after a couple of seconds.

Chen, W7AY

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