Service manual

Page 3
INSTALLATION - continued
Continuous Tone Coded Squelch
The 805 provides CTCSS or other tone decoder monitor or disable as a logical function
that goes low or to ground whenever the microphone is placed on a grounded hang up
clip. For applications that require a logical low or ground when the microphone is
removed from the grounded hang up clip, contact the CES Sales Department.
When installing the 805 microphone, ensure that the microphone hang up clip is
properly grounded to the vehicle chassis (add a ground wire if necessary) if using
CTCSS or other Tone Decoder hang up logic in the radio.
Combined TX Audio and Other Functions
For transceivers that require that the PTT signal is electrically sent from the
microphone on the same wire connection as microphone audio, then install an
appropriate resistor across jumper JPR3 on the 805 printed circuit board. Refer to the
Component Layout illustration for location of this jumper. For the value of this resistor,
refer to the original microphone circuit schematic diagram.
For transceivers that require that CTCSS or other tone decoder hang function and
microphone audio be sent on the same wire connection to the radio, install a resistor at
R15 on the 805 printed circuit board. Refer to the Component Layout illustration for
location of this jumper. On most radio models manufactured by Standard
Communications the value of this resistor will be 8.2K ohms.
MICROPHONE OUTPUT LEVEL MATCHING
Before beginning to set output levels, consideration must be given to the type of
microphone the radio uses and 805 jumper JPR1 (Refer to the Component Layout
illustration for location of this jumper):
Generally, JPR1 should be IN for radios using low impedance dynamic non-
preamplified microphones.
Jumper JPR1 should be removed for radios that use microphones with an internal
preamplifier.
The 805 is shipped with jumper JPR1 in place, except for certain 805 application
models where the jumper may already be removed for the specific radio type as
ordered.
VOICE AUDIO OUTPUT ADJUSTMENT
Set up a communications service monitor on the transmitter frequency of a desired test
or operational channel programmed into the radio. The use of an RF dummy load is
recommended. Adjust the microphone potentiometer RV2 (accessible through the
lower opening in the rear of the 805) while speaking in a normal voice so that the voice
peaks just go into modulation limiting as observed on the service monitor oscilloscope.
If the service monitor does not have an oscilloscope display, then it is suggested that
the 'demod' output be connected to an oscilloscope.