NHRC NHRC-4, Installation And Setup Gude

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NHRC-4 User Guide
2.6
The LED Status Indicators
The NHRC-4 repeater controller is equipped with five status LEDS that aid in setup and
troubleshooting. There are green LEDs for each radio port that indicate that the controller
has getting a valid CAS (carrier operated switch) and, if a CTCSS decoder is connected, a a
valid CTCSS decode signal. The appropriate green LED should light when its receiver is
active, and, if a CTCSS decoder is present, the correct CTCSS tone is present. The yellow
LED indicates that a DTMF signal is being decoded on the primary receiver. This LED
should light for the entire duration that the DTMF signal is present on the primary receiver.
The red LED's indicates transmit. These LED will light when its respective transmitter is
transmitting.
The LEDS can be disabled to reduce the power consumption of the controller. Remove
jumper JP2 to disable the LEDs.
2.7 Adjusting the Audio Levels
Audio Level Adjustments
Potentiometer Use
VR1 Secondary Receiver Mix Level
VR2 Secondary Transmitter Master Level
VR3 Primary Receiver Mix Level
VR4 Primary Receiver Level
VR5 Primary Transmitter Master Level
VR6 Beep Tone Mix Level
Preset all potentiometers to midrange. Key a radio on the primary input frequency, send
some touch-tones, and adjust VR1 (the primary receiver level) until DTMF decoding is
reliably indicated by yellow LED D5.
Note: If VR4 is set too high, a crackling noise may be heard in the transmitted audio during
the hang time. Reduce the level set by VR4 until this noise goes away. Any repeated audio
level reduction caused by adjusting VR4 can be compensated for by adjusting VR3 (primary
receiver mix level) or VR5 (primary transmitter master level.)
The primary radio's transmit deviation is set with VR5 (the primary transmitter master level)
on the controller board and the transmitter's deviation/modulation control. The key to
properly adjusting these controls is to remember that the limiter in the transmitter is
after
VR5 but probably before the transmitter's deviation/modulation control. The transmitter's
deviation/modulation control will set the actual peak deviation, and VR5 will set the level
into the transmitter. You do not want excessive limiting on normal speech going through the
repeater; it sounds bad and tends to "pump-up" background noise. On the other hand, some
limiting is desirable. An oscilloscope connected to the audio output of a receiver tuned to the
transmitter's frequency will show limiting as the audio gets "flat-topped" or clipped by the
limiter. Ideally, a 4.5KHz deviation signal input to the repeater should result in a 4.5 KHz
deviation output, and 5.5 KHz of input deviation should result in just under 5.0 KHz of
deviation out of the repeater. A service monitor (or two), deviation meter, and/or a signal
generator are necessary to do this job right.
Copyright
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2001, 2005, NHRC LLC. All Rights Reserved. Page 7