This dedicated ham-radio-oriented computer system simultaneously hosts an Echolink radio-to-Internet interface, an APRS personal webserver, and an APRN (SSTV-to-Internet) gateway. The objective was a dedicated box that contains both the computer system and the associated radios packaged so that the only external connections are antennas, Internet and 12 VDC power.
The heart of the system is the VIA Computing EPIA TC micro-ITX motherboard. This 8-inch square motherboard is a full X-86 computer with two real serial ports, 6 USB 2.0 ports, sound, ethernet, hardware-accelerated XGA video, standard and one standard PCI expansion slot. It also has standard headers for hard and floppy disk cable ribbons and the usual connections for front-panel leds, power and reset buttons, and USB ports. The board is supplied with VIA's own "Nehemiah" CPU (approximately equivalent to a 1 GHz Pentium III Celeron) already soldered in with heatsink attached. The board has standard tooling (mounting screw holes, ATX jack field, slot alignment, etc) to fit into any ATX-type case. It will also fit in very small footprint dedicated cases, including special ruggedized ones for mobile use. For ham applications, the real attraction of this board is that it runs directly off 12 VDC with no power supply needed!
[ The board was originally designed for car entertainment applications such as playing MP3s stored on a hard disk and hosting navigation systems. It is also the perfect platform for ham systems such as IRLP & Echolink nodes, repeater controllers, APRS digipeaters and igates, etc due to it's standard X86 architecture, direct 12 VDC input and low power consumption. Especially valuble for remote site applications is the BIOS power-recovery option that allows the system to automatically turn on when power is restored after an outage. ]
Instead of the usual multi-contact Molex connector for an ATX power supply, the board has a single 12-VDC-in coaxial power jack similar to a TNC or laptop. The board, by itself, consumes about 1.2 AMPS at 12 VDC . On-board regulators produce 5 VDC, 3.3 VDC and 1.5 VDC for the internal circuitry. The power conversion circuitry occupies about one-quarter of the real-estate on this board. A header near the front of the board provides +5 and +12 power to a set of standard yellow-black-black-red power cables for floppies, hard drives and CD-ROM drives. The IDE hard-disk ribbon cable connectors can also provide 5 VDC for laptop-type 2.5" hard disks that don't use separate power cables. Links for more details on this board are located at the bottom of this page. A close-up view of the bare board, showing the 12 VDC input and the added 2nd sound system is here.
This system simultaneously operates as an Echolink node on UHF (via the built-in sound system), as an APRS igate and personal webserver on VHF and HF, and as a APRN (Automatic Picture Reporting Network -- APRS and SSTV combined) server on a second 2M channel. The SSTV application uses a second added sound system (a standard Soundblaster 128 PCI inserted into the PCI slot).
With Windows 2000 and 512MB of RAM, the AGW Packet Engine, 4 copies of UI-View, Echolink, mmSSTV, LapLink (for remote access/control of the system) and various other utilities run with only about 20% CPU utilization, including handling two sound systems simultaneously. [ I have successfully received SSTV transmissions on 2M while an Echolink session was running on UHF at the same time. ]
With the CD-ROM drive disconnected to save power, the total drain at 12 VDC of the superserver, including the 7200 RPM IBM Deskstar hard drive, case fans, two transceivers and 2nd receiver is under 4 amps. The combination of nearly all peripherals integrated onto the main board, low power consumption and no normal power supply makes this board extremely quiet. I have heard absolutely no birdies or typical digital noises on any ham band HF through UHF.
The system is assembled into a standard large ATX tower case with four 5" drive bays. A Kantronics KAM TNC fitted into one bay, a Kenwood TM421UHF transceiver in the third bay and a Kenwood TM221 2M rig in the fourth bay. By an absolutely amazing coincidence, the mobile-mount screw holes on the sides of the transceivers lined up with the existing CD-ROM drive mounting screw holes in the drive bays ( ! ). Click here for a view.
The side view below shows how the tiny EPIA mother board leaves a lot of room for other devices inside the case. A VHF receiver from a commercial Repco repeater is mounted in the area normally occupied by an ATX power supply. This receiver is crystal-controlled on 146.700 and monitors a local repeater for SSTV transmissions and APRS Mic-E bursts.
One serial port is part of the standard rear-panel ATX jack field and is used by EchoLink for transmitter PTT keying and receiver squelch input. This is the typical sound-card-interface application where the handshaking lines of the serial port are used as single bit I/O , but the actual data lines go unused.
The other serial port is a 10-pin header on the interior of the motherboard. NOTE: VIA reversed TXD and RXD relative to PC industry conventions which caused me about 4 hours of grief before I discovered this fact. The standard PC "second serial port" cable assemblies WON'T WORK on this board! I made up a custom 10-pin-to-DB25 cable assembly (the grey flat ribbon in the picture) to connect this port to the KAM TNC used for both HF and VHF APRS data.
The APRN system uses a second TNC (KPC3+) to decode Mic-E bursts on the voice repeater. This required a third serial port. I used a serial-to-USB "dongle" plugged into one of the EPIA board's 6 USB 2.0 ports. I got lucky; in this installation; the driver for the dongle installed effortlessly and configured itself as COM3 on the first try! You can see the transparent blue USB converter and the KPC3+ under a coiled-up USB cable at the very bottom of the picture. The KPC3 and dongle are temporary. I intend to replace them with a USD $45 TNC-X KISS TNC with native USB support in the near future, freeing up the expensive KPC3 for other applications.
The Radio Shack prototyping board in the center bottom contains two homebrew opto-isolated soundcard interfaces. One connects Echolink to the UHF transceiver. The other connects the 1200 baud port of the KAM TNC to the VHF transceiver. Details on the sound card interfaces are here.
The rear panel contains antenna connectors for the three radios and a barrier terminal block to distribute 12 VDC power from my ham shack battery plant to all the devices inside. Since this system will often operate unattended for long periods, I individually fused each device with fuses rated only about 30% above the expected drain. If one device fails and blows it's fuse, it won't take down the entire system.