This post details the construction of the Mobile Packet Server project that I designed earlier this month. This server is a complete Windows Server, Packet TNC, and 40W VHF radio in a complete waterproof portable package. I used what I had on hand, a 30 cal. ammo can.

Next, I cut a couple pieces of 1/4" plywood the size of the motherboard (6 7/8" square) and the power supply (6 7/8 x 2") and match drilled the holes for screws. I used #6-32 flat head screws, and zipped them in to the holes with a power screwdriver into a nut on the top side. I then used some LockTite glue to hold the boards in place. These were the only things that required attachment, everything else was just held in place by the tight spaces.



Then I installed the main board...



and then the power supply and all the power wiring...



I installed the battery, the radio, the WiFi card, and last the TNC, which slipped nicely down between the radio and the motherboard. The battery and radio are on the right side, while the motherboard and power supply are on the left. The TNC goes between them, and it is easily lifted out if needed. The laptop hard drive was stuck vertically up against the battery and the flat ribbon cable folded up between it and the motherboard so it didn't touch anything, and was cushioned and held in place.

Here is the completed design:


I installed the optional external USB ports because it was so hard to get to the ports on the main board which are just below (above in this picture) the serial cable (white cable). With the serial port, the monitor cable, and the keyboard all going into there, it was easier to run the USB mouse off the external port.

This package is still on the air (shown below, in actual operation) since construction, and it is a self-contained unit that can run on its own without any physical connection to anything else for about an hour on the 7AH gell cell battery that is built-in. This includes the 12VDC monitor, which runs off one of the power cables coming from the battery bundle. The only thing required for operation is an antenna for the VHF radio. It has a spare power pole power connection (in addition to the input power connection), and a spare coax power cable to run another TNC or GPS if needed. Complete specs are below.

This RMS packet node for Winlink services the Redmond, WA area on 145.670 MHz FM simplex. The portability of this system gives the operator a significant advantage for emergency communications. The package is rugged, and literally requires only a mag mount antenna to be on the air in about 60 seconds from opening the box. An operator could throw it in his front seat, power it off his 12V power plug, and drop a mag mount 2m antenna on the roof and be able to have a mobile packet node able to be placed at an optimum communications point to support communications personnel.



Computer: Via Epia 600 main board and CPU, 512MB ram, 60GB laptop hard drive, 4 USB ports
Software: Windows Server 2003, and RMS Packet (by W5SMM and KN6KB)
Monitor: 12VDC KDS 17" LCD display, powered by coax connection from battery
Network: 100MB ethernet and 802.11B WiFi
Node Controller: KPC-9612 dual-port TNC, powered by coax connection from battery
Power: 7AH Gell-Cell lead acid battery, and external input - power pole connection on 2' cable.
Spare power pole and coax output connections also wired in to power/charge other devices.
Radio: Icom IC-228H 40W 2m VHF, powered by power pole connection from battery

Issues
In a real-world portable situation, I would probably want everything to be insulated, just in case. Being that it's inside a metal ammo box, anything could happen if it got jolted just right. This is just a proof of concept, but it seems to be working out well.

The board puts out about 15W or so of heat I figure, and it does not escape readily now, being that all the gear is jammed up against it, and it's in a box. The CPU and GPU are fanless, so they depend on air dissipation, which isn't happening in this design. I added a small 12V fan (not shown in the pictures) that connects to the spare power pole connection, and just sits on top of the motherboard at the lower left corner of the box. That fan moves enough air to keep it all cool and happy, but it isn't mounted it just sits there. And there's no fan guard, so watch your fingers. It's loud, and probably pumps about twice as much air as needed down into the case, so I may add a SPST switch across a 470 ohm resistor, in line with the +12 for a high-low switch.

There are no "front panel" controls for power, reset. The DIN connector is buried on the motherboard, and I'd have to figure out where to mount the switches.

There is no power switch. When the battery is connected, everything is live, since everything is wired directly back to the battery (to avoid noise and ground loops). I will have to add a 20A 12V SPST toggle switch someplace, which I can wire in-line with one male and one female spade quick-connect, to turn off the battery (and turn off the unit if not under external power).

The computer is S L O W. Its an old board. The newer fanless Epia boards have a bit more horsepower, but I think pump out a few more watts of heat as well and they cost a couple hundred bux. Perhaps there's a way to get the fan at the bottom of the case somehow. There are new Via board designs such as the Pico and the Nano that might better support this design, but they are even pricier. Plus they would take some custom connectors and some fancy wiring to make them interface with the rest of the system. Perhaps after I win the lottery...

Other than these minor things, it seems to be a fairly workable design. Feel free to post any questions.
73 de KD6GKD