RTTY
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[RTTY] interface cable for FSK?

To: <rtty@contesting.com>
Subject: [RTTY] interface cable for FSK?
From: wa9als at starband.net (WA9ALS - John)
Date: Thu Jul 31 08:39:07 2003
> I want to run FSK with my IC-756 ProII and WriteLog and have heard from
> several people that I should use my serial port for this instead of a
> USB port.  Does anyone sell a prefabricated cable to go from the ACC1
> connector (8 pin DIN) on the 756 to the DB-9 serial port?  Is there a
> better way to do this?

Tad, this isn't easy to answer in a brief email.  More people are starting
to get into RTTY, and that IS great!  However, there's a learning curve to
getting everything going to maximum pleasure, and how you wire up has many
possible variables, all tied to exactly what you want to accomplish.

If you want to operate RTTY, you first need to decide if you want to run
AFSK or FSK.  In the most simple terms, you will need for the computer to
supply PTT and RTTY signals (FSK on/off signals or audio AFSK tones) to your
rig.  Some "do PTT" via a rig control cable (CAT/CIV interface cable).  Some
do PTT using an "interface" consisting of a transistor switch in a cable
from their computer to their rig's ACC connector.

The simplest "interface" is a transistor switch consisting of one 2N2222 or
2N3904 transistor and one resistor in the cable.  You can make one cable to
handle both PTT and FSK if you use a 2-wire plus shield cable from RS.  For
PTT, you take the RTS pin of the COM port, thru a 1K resistor to the base of
the transistor.  The ground of the com port goes to the emitter of the
transistor and to the ground of your ACC connector.  The collector of the
transistor goes to the PTT pin of the ACC connector.

For FSK, you take the TxD pin of the com port, thru a 1K resistor to the
base of the transistor.  Take the ground of the com port to the emitter and
to the ground of the ACC connector, and take the collector to the FSK pin of
the ACC connector.  See http://www.w5bbr.com/pttfsk.html for lots of details
or Don's pages at www.rttycontesting.com.

If you want to operate AFSK RTTY, you will only need the PTT function of the
cable - or you could use CAT control PTT.  Then you will need audio cables
to and from the soundcard to the audio input and output of the ACC
connector.

If you don't like soldering to pins of com ports and acc connectors, I
advise soldering short lengths of small guage solid wire to make jumpers to
"bring out" the pins to where you can solder your cable wires with lots more
room to spare!  Radio Shack also carries DB-9 com connectors where the pins
are SEPARATE.  You solder the pins to the end of your wires and THEN put the
pins into the DB-9 - works great!

So solidify your goals and questions, and then keep asking!  GL - 73 - John,
WA9ALS


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