My FT-920 works wonderfully on just once Comm. port for everything. Here
are the steps to duplicate what I did.
(1) I picked up a 6 foot modem cable. The cable has a DB-9F connector at
one end and a DB-9M at the other. It was wired 1:1. NOTE! Either a "modem"
or "null-modem" cable will work since you end up cutting the cable and
rewiring the two ends. The big thing is to have the corrector connector
sexes.
(2) Cut the cable into two pieces approximately 12 inches from the DB-9M end
(radio end).
(3) I purchased the 2x3 inch plastic project box from Radio Shack. If I
make another one I would get the next larger size! Working with the 2x3 was
tight.
(4) I drilled a small hole in both ends of the box just large enough to pass
the cable through. I left it very tight on purpose so that I could then put
a tie-wrap on the cable inside of the box to keep it from slipping out. On
the radio end I also drilled holes for and mounted an RCA phono-jack (for
PTT) and 3.5MM (1/8") mono-jack. The choice of which jacks to use is up to
you.
(5) Next I wired up a small perf-board with two opto-isolator circuits for
the PTT and CW. Shown below is a crude schematic of each circuit. The
input (computer) end is shown on the left.
.--------------.
| |
DTR/RTS >------[R1]---+--------+ (1) (5) +------- CW/PTT
| _ | |
[D1] ^ | 4N33 |
| | |
computer >-------------+--------+ (2) (4) +------- radio
ground | | ground
`--------------'
R1 is a 560 ohms, 1.4 watt resistor and D1 is any old silicon signal diode
such as a 1N918 or 1N4148.
(6) Here are the connections
+--------+-------+-------+
| Signal | DB-9F | DB-9M |
+--------+-------+-------+
| xmit | 2 | 2 |
+--------+-------+-------+
| rcv | 3 | 3 |
+--------+-------+-------+
| DTR | 4 |xxxxxxx| to "CW" opto-isolator
+--------+-------+-------+
| Gnd | 5 | 5 | also to opto-isolator input gnds
+--------+-------+-------+
| RTS | 7 |xxxxxxx| to "PTT" opto-isolator
+--------+-------+-------+
My total cost outlay for the cable was probably in the 20/30 dollar range
when all was said and done.
Hope this helps. If anyone wants a copy of my hand drawn schematic and some
picture of the cable (printed on computer paper) feel free to send my an
SASE. My address is in the call book.
Cheers and Happy New Year to all,
-ricK1log/7
-----Original Message-----
From: Marty Tippin
Subject: [WriteLog] Rig Control & PTT
Anyone know of a good way to split out the DTR (or RTS) signals on the rig
control serial port? My FT-920 doesn't support PTT on the rig port, but if
I could get to DTR or RTS on that same serial cable, I could route those
through an optoisolator to drive the external PTT on the rig. I suppose
there must be some sort of "breakout box" you can put in line with the
cable but not sure what it is or who carries it.
Any ideas short of building my own custom cable?
-Marty NW0L
martyt@pobox.com
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