Appendix C – Common Modifications
Extended
Audio
Level
Range
When
to
use:
Use
this
modification
when
the
audio
drive
level
cannot
be
set
high
enough
for
your
radio.
Explanation:
The
OpenTracker
is
normally
supplied
with
a
conservative
value
for
R2
to
reduce
the
possibility
of
overdeviation
and
distortion.
For
a
minority
of
radios,
this
results
in
an
audio
level
that
is
too
low.
Procedure:
Replace
R2
with
a
lower
value
resistor.
Halving
the
value
of
R2
doubles
the
audio
level
adjustment
range.
PTT
Signal
Method
When
to
use:
Use
this
modification
when
the
OpenTracker
is
used
with
most
mobile
radios
and
certain
handhelds.
Explanation:
Most
handheld
radios
signal
push
‐
to
‐
talk
by
pulling
the
microphone
input
to
ground
through
a
known
impedance.
R3
normally
serves
this
purpose
in
the
OpenTracker.
It
is
not
required
for
mobile
radios
and
certain
handhelds,
most
notably
those
made
by
Kenwood,
and
may
cause
them
to
transmit
continuously
if
installed.
Procedure:
Omit
R3.
For
certain
types
of
handhelds,
especially
commercial
models
(e.g.,
Motorola
GP
‐
68)
it
maybe
be
necessary
to
use
a
lower
value
for
R3.
OpenTracker Manual - Version 1.05 – 6/25/06
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