DC powered micro computer

I’m in the process of building a amateur radio digital voice repeater (Dstar protocol).  Several in the area have talked about erecting a Dstar repeater since Icom introduced equipment 6-7 years ago, but the price of Icom’s stack (repeater, controller, gateway software) exceeds $3500 and then one needs a user radio (handheld transceiver and/or mobile rig installed in car or home) which ran $500 and up.

Dstar specifies the handling (layer 3 OSI) of the data stream, but currently Icom only uses the rather old GMSK modulation scheme with no time division.  This makes using off-the-shelf narrowband FM gear possible – and with commercial PMR/SMR users having to narrowband again for 2013 there is more and more quality synthesized gear on the used market from the past 20 years available on the cheap ($25-75 common for a 25 watt 150 or 450Mhz radio that can be programmed into amateur 144-148 or 440-450 ranges).

Without going into the evolution of modem hardware boards, or the discussion of using a modern computer with a soundcard to demodulate the GMSK signal from the radio’s discriminator and modulate direct FM to the transmitter, I like the simplicity and reliability of hardware encoding and decoding. 

One of the best boards available today is the Star*Board manufactured right here in Iowa by Matrix Circuits and distributed by MoenComm for $119

Now back to computers.  I needed something small-ish, but inexpensive.  Preferably running on 13.8vdc common with the radios for emergency power.  I’ve had a Lenovo X120e Netbook for almost a year running the inexpensive, energy-efficient AMD Fusion chipset and processor.  I thought about ‘sacrificing’ the netbook to this project, but a screen wasn’t required, and the unit took 20vdc input.  I quickly decided against 24v power for all equipment – KISS principle and all.

Hey, Asus has a micro ITX form-factor board for the AMD Fusion – and with the processor installed with a big heat sink (read: no need for fans) under $115.  And it consumes less than the PicoPSU power supply so off to Amazon I go:

The computer bundles together quite nicely, and the case is nice quality metal, except for the faceplate which I consider somewhat cheesy in that you have to unscrew (one screw) the cover and slide out to remove the faceplate.

The pix.  Showing the back of the case – the PicoPSU coaxial jack for 12/13vdc is on far right

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Front panel sans faceplate, showing power button and two USB jacks.  These are inaccessible behind faceplate, suggested use is for USB WiFi or bluetooth radio.

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