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Mk 4 Repeater controller - August 2017

A linking three way controller


Primarily designed to work with the TAIT remote station modules this controller provides complete management of one duplex repeater and two associated radio links. It is anticipated that the completed repeater station would sit between two other sites receiving and supplying audio of a fixed level (-10dBm) from/to both linking units thus simplifying the setup processes.The unit will replace a VK5DJ Repeater Controller Mk1 (with only one linking port) and its associated audio circuit.

The key design goals were to achieve ease of setup, flexibility and useful options.

The common point of the audio mixer is available on connector CN6 to facilitate either a CRO or other level monitoring. The audio stages are designed to mix the various signals without affecting load impedances. The intention is that -10dBm input on any of the 5 inputs to the audio stages will result in -10dBm output on all the outputs of the audio stage. This design uses top cut filters on the PIC pins presenting beeps/callsigns/messages as good sine waves. There are level controls for the CW output, the 1kHz test tone and the CTCSS and DTMF decoders.

The absence of other level controls is intentional, the TAIT receivers and exciters have line level controls so the audio section provides mixing only. The audio bridge portion is designed to work with audio in/out at -10dBm with 600 ohm load.

The controller manages the PTT of the main repeater and associated radio links. Each transmitter can be enabled or disabled, and control of TX functions can also include CTCSS control.

Timeouts are fully flexible on main timeout (mins), callsign (mins), length of tail, presence of courtesy tones etc. etc.

Three callsign modes are supported.

The setup can be managed by DTMF and/or locally using a keypad and LCD. The latter being fed from a 16 bit expander chip (MCP23017) driven by the I2C bus from the PIC18F2480. A useful addition to the DTMF controls is the capability to change the password from the keypad.

A complete list of functions is shown later in this document, see Table 2.

To ensure correct sequencing for simplex links the controller, on receipt of a COS, provides outputs (active low) to disable the inactive receivers. For example an input on the Repeater receiver disables the two link receivers, then activates the two link transmitters (assuming they are enabled in settings). On loss of repeater receiver COS the transmitters are first shut down then the receivers are activated. There is no de-activation of the repeater main receiver as it is a duplex system and local input always has precedence over the links.

A Watchdog timer operates in the controller and protects against lockups. It is set for one minute. If for some reason the system crashes or if you are in the remote control mode for longer than one minute the watch dog timer will reset the controller and reload settings from EEDATA storage.

Summary of features

The various modules making up the controller are shown below. The two expander chips and their associated modules (LCD/Keyboard, LEDs sound recorder modules or the audio level bar graph are not essential. The controller works fine without them using DTMF

More information to come as the project progresses. At present it is in Beta. The hardware has been built but will be test run from the Bluff Site and the Naracoorte site before final boards are manufactured. We have not yet decided if the project will be made available although the chances are good. The hardware uses surface mount technology which some hobbyists may find difficult to solder.

Circuit Expansion Interfaces 1_1.bmp

Design and construction team:                                                     Download circuits and hex

                            Brian VK5VI                                  John VK5DJ                               Barry VK5BW

Repeater Controller Variant 1_2B circuit.bmp