NHRC-3/M2 Repeater Controller
Installation Instructions

These instructions will guide you in the installation and adjustment of the NHRC-3/M2 repeater controller.


  1. MASTR II Preparation
  2. TS-32 Hookup
  3. Installing the NHRC-3/M2 in the MASTR II
  4. The LED status indicators
  5. Installing the Audio Delay
  6. Adjusting the Audio Levels

Board Layout
  1. MASTR II Preparation
    If you are planning to operate the MASTR II with the NHRC-3/M2 as a full-duplex repeater, then you must have the duplex modification done before installing the NHRC-3/M2. Consult the NHRC MASTR II infosite for duplexing information.

    There are two options for interfacing the CAS and TX audio to the controller. These signals do not appear on the the CTCSS plugs on the system board of the MASTR II.

    Option 1: Use an interface cable

    Transmit audio and CAS appear on the controller at J1, a 3-pin header. Wire an interface cable as shown in the table below:

    J1 Connections
    Pin #
    1MIC HI
    J902 #6
    J904 #9
    3MIC LO
    J902 #5

    Option 2: Modify the MASTR II System Board.
    By cutting one trace and adding two wires to the MASTR II system board, the jumper described in option 1, above, can be avoided.

    Add a wire that connects P908 pin 2 to J902 pin 6 (the exciter's MIC HI input). Cut the trace that leads to P908 pin 3 on the system board, and add a wire that connects P908 pin 3 to J904 pin 9 (the CAS signal from the IFAS board). Install 0 ohm resistors (jumpers) R34 and R35 on the NHRC-3/M2 board5, enabling the TX audio and CAS signals on the J908 connector. (Note: If you plan on using the local microphone on the MASTR II's control head, install a 1.5K resistor in location R34)

  2. TS-32 hookup
    Connector JTS32 is a 5-pin header that allows the easy installation of an optional Communications Specialists TS-32 for CTCSS decode and encode. Wire JTS32 to the TS-32 as follows:

    JTS32 Connections
    Pin #
    1+V POWER
    5- GROUND &

    The TS-32 must have the JU-2 jumper cut. If you want to be able to disable the CTCSS requirement, install a switch on the HANGUP lead. The TS-32 will supply CTCSS encode tone to the exciter through the NHRC-3/M2.

    Adjust the CTCSS deviation with the R29 on the TS-32 board, with the "CG LEVEL" pot on the MASTR II exciter set to midrange. The ideal deviation for the CTCSS tone is 250-300 Hz.

    Consult the TS-32 INSTRUCTION SHEET for details on setting the CTCSS frequency.

  3. Installing the NHRC-3/M3 into the MASTR II
    The controller installs in the MASTR II where the MASTR II "Channel Guard" board normally belongs, plugged into the top of the systems board in the front of the radio. If you have not already removed the Channel Guard board, do so now by pulling it straight up and out of the radio. The NHRC-3/M2 installs with the component side of the board facing the control head cable connector. Carefully line up the P908 (left side) connector with the pins on the system board. The P909 connector may not cover all the pins on the right side; this is ok, since that connector is used for physical support of the controller only. Push the board down firmly until the connectors are right against the system board. The controller is now installed.

  4. The LED Status Indicators
    The NHRC-3/M2 repeater controller is equipped with three status LEDS that aid in setup and troubleshooting. The green LED indicates that the controller is getting a valid CAS (carrier operated switch) and, if the TS-32 is connected, a valid CTCSS decode signal. This LED should light when the repeater's receiver is active, and, when the TS-32 is properly installed, the correct CTCSS tone is present. The yellow LED indicated that a DTMF signal is being decoded. This LED should light for the entire duration that the DTMF signal is present on the receiver. The red LED indicates transmit. This LED will light when the transmitter is transmitting.

    The LEDS can be disabled to reduce the power consumption of the controller. Remove jumper JP2 to disable the LEDS.

  5. Installing the NHRC-DAD with the NHRC-3/M2
    Remove the jumper between pins 2 and 3 of J2, then plug the cable from the audio delay board onto the J2 header. If the audio delay is not installed, then the jumper must be present between pins 2 and 3 of J2.

    The NHRC-DAD is small enough to fit in either the exciter "bay" or the oscillator/multiplier "bay" of the MASTR II chassis. Carefully route the cable to either of these locations. You may need to file a small notch into the plastic chassis to make room for the cable to pass through to the NHRC-DAD board.

  6. Adjusting the Audio Levels
    Preset all potentiometers to midrange. Key a radio on the input frequency, send some touch-tones, and adjust VR1 (the main receive level) until DTMF decoding is reliably indicated by yellow LED D4.

    Deviation is set with VR2 (the master level) on the controller board and the "MOD ADJUST" control on the exciter. The key to properly adjusting these controls is to remember that the limiter in the exciter is after VR2 but before the "MOD ADJUST" control. The MOD ADJUST control will set the actual peak deviation, and VR2 will set the level into the limiter. 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.

    Adjust VR6 (the beep level) to set the courtesy tone and CW tone level.

    The easiest way to adjust the ISD2590 input and output levels is to select the simplex repeater mode and record and play messages until the audio sounds right. VR3 adjusts the record audio level into the ISD2590. Adjust this control for the best sounding record audio. VR5 sets the ISD2590 playback level. Adjust this control for best acceptable transmitter deviation. Note that the ISD2590 includes on-chip limiting/compression; this may fool you into thinking that you have the input level set just right when it is really too high. Try recording a whisper, it should play back quietly, also try recording normal speech with large gaps between words in a somewhat noisy environment to listen for background noise pumping. Properly adjusted, the ISD2590 recorded audio should be indistinguishable from normal audio repeated through the system.

    VR4 is used to set the receiver audio level, and may not need to be adjusted from midpoint.

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/nhrc-3m2/installation.php, version 1.21, last modified 02 January 2005 12:29
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