Specifications

rcoM tc2sNEljl
Receive
audio
may be obtained from IC1,
pin
9, on the
RF unit. Transmit audio
may
be
injected at R-45,
at the
end not connected to trimpot
R-100. Use a
33KW
resistor in series to correct signal
levels.
rcoM rc3200A/E
Receive
audio
may
be obtained at
ICl
pin
9
(main
board)-this
is a common receiver chip for both bands.
Transmit
audio
may
be
injected
at
D3's
cathode
(VHF)
and
Dl's
cathode
(UF{F).
KE NWOO D T M221, TM32 1 A,T M421
Receive
audio
may
be obtained
at ICl,
pin
9
(IF
board).
Transmit audio may be injected at connection
#7
on the VCO
assembly on
the TX/RX unit.
KENWOOD TM621
,
631
and 721
(courtesy
of Jeff
Angus, WAOFWI)
Receive
audio is taken fiom the discriminator output, Look for the 3.3KW
resistor coming off
pin
9 of the
last IF stage. Connect a IKW series resistor from
the modem
RX input to the
junction
of the.001mF
ca-
pacitor
and
the
3.3KW resistor.
PTT is
taken
fiom
pin
2
on the microphone connector. Transmit audio is fed through a
IKW series resistor
to the top
of
VR3
(the
deviation control).
Ncnn:
This
method has been tested and works
quite
well on 440 MHz and
220
MHz.
The motls haven't
fully
been
tested on the 2-meter
portion
of the
radio.
As with
any
modifications,
take reasonable care-the radio is full of surface mount components.
KENWOOD TR751
Receive
audio may be obtained atIC2,
pin
9
on the RX unit. Transmit audio may be iniected by
way
ol the
cathode D2 l.
KENWOODTS-790
(courtesy
James
Miller,
G3RUH
&
Sueo
Asato,
JAOFTL)
These mods work
well with
9600
bps
UO-14
and
CBBS
operation.
(Ref'er
to G3RUH's notification on
FT736R
for more details. ruVTX mod suitability remains
the same as
his notes.)
Receive: Detected
and amplified/buffered FM direct from the receiver discriminator is available
from Pin
9,
ICI
(Sub)
or IC8
(Main).
I use ICI
(Sub)
for reception.
Transmit:
Inject
your
transmit audio at the cathode side of diode D8 I with a l KW resistor
in series.
(You
can flnd D81 near
Q73
in
your
IF UNIT diagram.)
KENWOODTW-4000
(courtesy
of Mike
Curtis,
WDOEHR)
The
radio's filters look
good,
although digitally
optimized
filters
such as MuRata SFG-455D
or SFH-455D
would
allow a tighter
passband.
The
radio also uses a separate transmit oscillator common to both
144
and
430
MHz for
generating
FM-a crystal, inductor, and a varactor
to
produce
nice, linear FM-and
hetero-
dynes up from there to the respective bands.
The mods
for transmit
audio
and receive
audio are:
Receive:
Thck a 4.7KW resistor to IC-1,
pin
17. Tfansmit:
tack a 6.8KW
resistor to the cathode
of D16
(unction
of C125-R95-Dl 6).