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Mk 2 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 touch keypad on a 320*240 graphic LCD. The latter controlled by a PIC18F25k22 as a slave from the main controller 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 below.

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 the watch dog timer will reset the controller and reload settings from EEDATA storage. There is also a safety mechanism for the graphic display. If by accident it is left in other than display mode it will automatically return to display mode after ten minutes. The screen blanks after 10 minutes of no use to protect the LCD. A touch brings it back.

Summary of features

Design and construction team:                                                     Download circuits and hex

                            Brian VK5VI                                  John VK5DJ                               Barry VK5BW

Summary of commands for the Mk2 Repeater Controller

Commands may be sent by remote DTMF or locally from a touch screen. The item numbers are identical for both methods but only the keyboard may change the password and the type of voice recorder while only the DTMF system may begin a recording session.  DTMF assumes that a password is sent first with a star prefix. Example *987. In the command/function list square brackets indicate the function which is then followed by the data.

All DTMF commands and data use two digits e.g. 01,02,03,....99. Here is the Table 2 summary.

Above: An overview of how VK5RMG is setup. An expansion board has been fitted to enable 3 link ports to be used. The expansion board splits the Link two port on the main controller into two - providing an additional port. Normally the controller would be limited to two ports. The expansion board is a separate project and is located in an additional chassis at VK5RMG.

The main board:

1) power to 5V regulator at top with programming to right.

2) on left the interfaces from top: Repeater, Link1, Link2,, Red I2C out and audio inside.

The opto couplers are in sockets so that in case of damage in the outside world the chip can be replaced. Experience talking.

The graphic and touch controller.

This board also measures the 12V supply to provide the onscreen voltage readout.

J1 spare connector for expansion.

J3 input from main controller

J4 is the connector for the audio record board if used.

J5a/5b connector for the graphic 320*240 display with touch.

J6 3V3 voltage regulator