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Exeter Raynet 2017 Repeater Controller

The Exeter Raynet 2017 Repeater Controller is designed to be attached to the two solar-powered batteries at the repeater site. As well as producing the functions of a standard repeater controller, it measures the battery voltages and transmits the UTC time, battery voltage values and internal temperature in Morse code every hour.

The message output is typically: GB3EX C 13Z A 12.9 B 12.7 T 22

The unit has the following inputs:

  1. Battery A
  2. Battery B
  3. 12 volt power
  4. CTCSS valid
  5. Reset

And the following outputs:

  1. Isolated normally open contacts to switch the transmitter on (PTT loop)
  2. Audio output to transmitter

The controller draws power from a switched 12 volt supply on the telemetry control unit. This means that an operator can send the correct command and switch the repeater controller off, thereby disabling the repeater.

Measured current drain at 12 volts is 60 mA when the transmitter PTT is enabled and 50 mA in standby.

The controller functions are coded into an ATMega328 micro-controller. Changes to the service design require the controller software to be altered by removing the ATMega328 integrated circuit, placing it in an Arduino Uno. reprogramming it and placing it back in the controller.

The controller has no external controls or separate power supply. To reduce corrosion of contacts in the harsh climatic conditions, adjustable components have been reduced to just one: the audio level control.

Kicad was used to prepare the circuit diagrams.

The Arduino IDE was used to write the code, compile and upload it to the ATMega328.

The encoder is housed in weatherproof Eddystone box with wires from the PCB connected to an external 10 way terminal block.

The current version is V4, dated June 2017. This version added:

  • Real time clock module to keep accurate on-the-hour time-keeping for idents.
  • On-the-hour voltage announcement begins with the UTC hour of day and after the voltages, ends with the internal temperature in Celsius.
  • Bubba oscillator for low distortion sine wave generation of the 660 Hz Morse tones.
  • Improved accuracy of voltage measurement so it is now 1% accurate.
  • Opto-isolated push-to-talk button operation.
  • Increased current drain to 50 mA because of the additional components.

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