Specifications

"Mod"
Notes for
Specific
Radios
It's almost
embarrassing to call some
of these
"mods"-you're
only bringing out terminations ol'existing
signals;
bringing out these connections from
your
FM transceiver is a
"nondestructive"
modiflcation to
your
transceiver, except
lbr the ALINCO DR-1200 and the ICOM IC-22A
modifications-these
radios
will
be dedicated to
9600 bps data
radios
afier their modifications are
perfbrmed.
ALINCO DR-1
10, DR-l 12, DR-l200
This
mod uses the microphone
jack
for both
9600
bps transmit and receive. As
you
read in thc
preceding
paragraph
about the DR-1200,
after the mod
you
won't be able to transmit FM voice, but
you'll
stillbe
able to receive
FM voice.
Receive:
Disconnect the
pink
wire
that
goes
to the DATA OUT
pin
of the mic connector on the circuit
board,
then reconnect it to
pin-2
of
the IF
board's connector. This connects the received audio
fiorn
the
mic
plug
to the radio's
discriminator.
Transmit:
Remove resistor
R3 I on the main board-this is a chip resistor located on the solder side of the
main PC
board.
(Note:
if
you
de-solder the
part
and
resolder it
so that only one edge of
it is still connected
to the board,
you
can more
easily return the radio to 1200 bps-and FM voice-operation il'nccdcd.) Re-
move chip
capacitor C40, then resolder it to
the circuit board so that one end ol'the capacitor
is
connected
to the
pin-7
of the VCO board
and
the
other end is straight r"rp in the air. Connect a
jumper
wire
between
the fiec
end of C40 and the
"hot"
end-the end not
grounded,
or the end electrically furthest away
liom
ground-ol'
C35.
(Note
that C35 is next
to the resistor R3 I
you
removed earlier.) The mic input is now
connected to the VCO lbr
9600 bps operation.
GE
Phoenix
and GE PSX-200
(courtesy
of
William N.
Goodman,
K3ANS and K3HKZ)
These radios have
a
Data Iniack,
J-301. It is next
to
the data levelcontrol, R-212, midway on the right side
of the radio looking with
the top up,
I'rom
the fiont of the radio. Run a thin 22
guage
wire
liom
J-301 to
pin
5 of J-9l I on the
back. Remove the W-910
jumper
fiom hole
85 to
hole
86.
This removes thc rnike
high input
through the mike audio
preamplifier.
This enables the radio to work with
9600
bps.
ICOM
224
(courtesy
of Mike
Curtis, WDOEHR and Dave
Shalita,
W6MIK)
This is
one o['the more difficult rigs
to modify. It converts
your
IC22A into
a dedicated 9600
bps
packet
radio.
Cornponents with an
asterisk are added to the crystal board.
l.
Remove the trimmer
capacitor
for
the transmit crystal socket
you'll
be using for
9600
bps. Replace
with
the above circuit. The 4pF-20
pF
trimcap should be a
good quality
ceramic or other low-drift
trimmcr.
(Sony,
Radio
Shack doesn't have anything suitable.)
2.
Connect
two
l0KW
resistors to C53
(both
sides)
and tie the other ends together.
This
iunction
is
where
you'll pick
ofT
your
receive audio.
3. Turn R67
(deviation
control next to P-l and P-2) fully
countcrclockwise-this
kills
any signals that
may get
into the
phase
modulator.
4.
Using a service monitor,
or oscilloscope connected to the detector of a receiver, adjust the
varactor
bias fbr the best
eve Dattern.
rcoM rc290A/H
Receive
audio
may
be obtained atICl2,
pin
9, on the
main
board. Transmit audio can be injected at
D3's
cathode
on the
main
board. If
you
still have the mating ACC
connector
plug,
connections
can
be added
to
ir.