Wednesday, January 23, 2013

Antenna Data!

Over the past few months, I have been collecting data on different kinds and styles of antennas and am finally getting around to publishing the information.  I've created a separate page on this blog to keep the data and will update it when I get more antennas tested.

Thursday, January 3, 2013

KC0ALC-1 Digipeater

KC0ALC-103 HSMM-MESH router

The current iteration of my digipeater is a WRT54GSv1 router, running APRS4R which is written in Ruby.  The Ruby packages for OpenWRT takes up more than the available memory space on other routers (G and GL versions) so I'm using a GSv1 that has more flash and memory to handle both APRS4R and HSMM-MESH™ firmware.   Previously, I had been using a WRT54Gv2 router with the USB modification and had the OS running on a flash drive, later on an external 2.5" hard drive.  The USB sticks would die after a month or two of usage and the hard drive required a USB hub to provide enough power so I decided to upgrade it to a GSv1.

The TNC is a TNC-X v1, KISS only TNC that I bought at a swapmeet for $5 and the radio is a FM-2030, a 70s vintage mobile radio that I had no other use for.

The TNC is connected to the router via one of the built-in serial ports on the WRT router.  I found a TTL-RS232 converter chip laying around that works on a 3.3V Vcc voltage (ICL3232) so I wouldn't have to add any other voltage regulators. I made up a simple interface-board, dead-bug style, for the converter and used a couple of DB9 cables to provide external

Other additions to the router include a heat sink on the main processor and a fan inside the case to circulate air.  The fan is a 12V fan I found in a junk box with a current limiting resistor to slow it down.  Since this router will be running 24/7 I wanted to minimize the thermal stress on the components.



APRS4R is running as a fill-in digipeater (only responds to WIDE1-1 packets) and also a transmit I-Gate, limited only to the polygon weather alerts coming through the APRS-IS servers.  I further limit the packets to my county and surrounding counties via the APRS-IS filtering I have set up.  I'm using APRS4R right now mostly for the ability to share the APRS data and have other computers connect to the digipeater and use it as a TNC interface.  I have the port forwarded through my home router so I can access my TNC wherever I have an Internet connection and also available to any HSMM-MESH™ routers that are connected to the router.

APRS4R also needs regular restarts to behave correctly (due to a memory leak issue, I believe) so I have a cron job reboot the router at specified intervals.

Here is an overall system diagram:


Some pertinent links: