New Controller Technical Details
The controller is an off the shelf Link Communications RLC-3 controller with four repeater cards (one for phone patch, and one for each repeater). The controller also contains an audio delay module on each radio card and a phone line interface. We also have a digital/analog card for local measurements.
The 144 and 440 repeaters are new Vertex 25 watt repeaters, with two minor modifications needed to allow operation in our environment.
The 220 receiver is a 150 mhz Motorola Motrac receiver with helical resonators and a front-end crystal filter. We added a high side converter to mix 220 down to the 150 Mhz receiver. The 220 transmitter is a Hamtronics 10 watt transmitter stuffed in a rack mount box.
The interface box was designed and constructed by your technical committee. It is physically larger than the controller. It has 24 RJ-45 connectors to interface to everything except the cable to the digital/analog card (DB25). Power is directly from the 12V battery, a 7805 is used to get 5V for internal logic
The interface box contains a place for a 12V modem (currently replaced by the laptop), a control panel setup for 6 repeaters, and a touch tone microphone that can act as a simulated receiver for local control. An audio amp and speaker monitors the selected transmitter. The interface box contains up to 6 interface cards (2x6 inches), and a motherboard that simplifies wiring and contains misc. common logic and amplifiers.
The interface cards contain CMOS logic to handle logic and analog switching plus an interface for MIC-E control.The serial out from each radio channel in the controller is used for various repeater specific control circuits, and drives a 7416 deserializer which has open collector outputs that directly drive all switched functions.
Each repeater has two RJ-45 connectors (xmit and rcv for 220, repeater control for 144 & 440). Additional RJ-45 connectors are used for MIC-E control, phone line monitoring and modem, power supply monitoring and control, and misc functions. Hey, RJ-45 cables and such are cheap, reliable, and plentiful.
The modifications to the Vertex repeaters were to enable low power switching on the model without the internal power supply, and the rewiring of the DB25 connector to get the low power control line out. When on battery power, the Vertex repeaters are switched to low power (5 watts) instead of their usual 20 watts. The Vertex DB25 connector also supplies S-meter, squelch control, and address lines used for PL control. We interface to the DB-25 through a DB-25 to RJ-45 adapter connector.
Software was developed for the controller, but we found several "features" in the controller that made for challanges. There are no variables for storing the state of the serial port which made us use many nested macros. There is no capability to collect repeater usage statistics. Macros have a size limit, so they had to be split, tricky for code changes. The controller is not a friendly modem user, not understanding flow control, and is easy to overrun. Although comments are allowed, it is not easy to organize code for the case of a total reload. The language is like using a native p-code with 3 digit decimal operands, which is hard to read.
After playing with several schemes to solve these problems, we ended up building a simple compiler using PERL that generates the code for the controller. This allows symbolic references, indirection, and automatic macro splitting when needed. The modem problem was more difficult. To solve the modem problem and to allow for greater control of the repeater, a donated Compaq laptop is used. It contains a 56K modem and interfaces to the controller via its serial interface. The laptop stores the source code and documentation, and allows any newly compiled code to be sent to the controller at reasonable speeds. The laptop, running Linux, is fully TCP/IP connected, allowing it to 'phone home' to report problems if necessary. The laptop can do statistic gathering, which has not yet been implemented.
These technical details will be expanded in the future.