Welcome to the Equipment tour
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The repeaters are made from Motorola Mitrek recievers. A circuit board on the outside does the power supplies, audio buffering and level setting, volume, squelch, etc. It provides a standard interface into the repeaters. There are four RCA jacks (audio out, xmit audio in, SQL detect, PTT) and a 25 pin connector pinned out for an SCOM 5K controller. There is an inside board which buffers the audio out and creates pull to ground digital signals for the squelch, PL receive, and xmit PL. The Mitrek and the boards are put on a rack mount shelf that can also hold the controller. The entire system is 3 RU tall (so budget 4 RU in the rack).
(87K, 26 seconds)
A link radio- the Mitrek and the interface boards (both external and internal). The other PCB is the PL board for a Mitrek.
(79K, 24 seconds)
A repeater unit. Note the separate input and outputs. A 4 LED display showing receive squeltch, receive PL, xmit PL, and PTT is mounted at the front.
(80K, 24 seconds)
Upper left: The internal board for the Mitreck. Bottom: The LED display unit, which can be used for testing or mounted on a unit. Upper right: A board used to turn on fans or heat if things get too hot or cold. Used in various places for thermal control.
(86K, 26 seconds)
The exterial interface board. The connector at the lower left is a 15 pin connector that connects to the Mitrek. Pin 1 to pin 1, etc. The wires are tack soldered onto the pins. A bit kludgey, but it works. Above that are the volume and squelch pots. Beside that are two transistors that connect to a temp sensor to activate fans and heaters if the unit is too hot or cold. Above that is the 16 pin connector that connects to the 4 LED board or to the controller. Below the TO-220's is a pot that controls the xmit level. At the bottom of the board are the RCA jacks used for bench testing. They also make a good "is the RF deck OK" test, since you can loop the audio and the control signals and make a dumb COR repeater. Bottom right is the 25 pin connector with all the audio and control signals pinned out for a SCOM 5K, the "backup controllers" used on some machines, and the primary controllers for the local 2M machines. On the right, you can see the 5V switching supply. The unpopulated area is the 28 volt to 12 volts supply used only at the Efland site. The big diodes are transient protection diodes on all inputs, outputs, power inputs, and regulator outputs. The board takes the +13.8 (or +28) and makes -5, +2.5, +5, +8, and +13.8
(86K, 26 seconds)
This is the PCB with the 68HC12 that is used in the controller. It connects to the audio switching board via a 10 wire connection, with all IO done serially to the audio controller. It has two serial ports, a 10 segment led bar, a 12 bit D/A for voice announcements, 1 M of flash, and 64K of RAM.
(89K, 27 seconds)
The audio switching board takes the 16 pin connection from the interface board to talk to the RF deck. It can also connect to up to three other RF link decks via their 25 pin connector. It has the audio delay circuit for both squelch tail suppression and PL decode time compensation (see "how it works" document). There is a 2500 gate FPGA that runs the D/A's, A/D's, and some other functions. The board can also work as a stand alone controller, including Ider and timeouts, if the dip switches are set right. It can also be just an audio delay board that takes the 16 pin in and outputs a 25 pin SCOM 5K output. This is how the 2M machines get an audio delay. It has the touch tone receivers and xmitters on it. Leds show the status of the main RF deck, which radio (main or one of 3 links) is in control, the touch tone digit being received, and the state of the power supplies.
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(79K, 24 seconds)
(80K, 24 seconds)
(86K, 26 seconds)
(89K, 27 seconds)
The audio switching board takes the 16 pin connection from the interface board to talk to the RF deck. It can also connect to up to three other RF link decks via their 25 pin connector. It has the audio delay circuit for both squelch tail suppression and PL decode time compensation (see "how it works" document). There is a 2500 gate FPGA that runs the D/A's, A/D's, and some other functions. The board can also work as a stand alone controller, including Ider and timeouts, if the dip switches are set right. It can also be just an audio delay board that takes the 16 pin in and outputs a 25 pin SCOM 5K output. This is how the 2M machines get an audio delay. It has the touch tone receivers and xmitters on it. Leds show the status of the main RF deck, which radio (main or one of 3 links) is in control, the touch tone digit being received, and the state of the power supplies.