Todd has built me up as an extra-class ham that might know something. I hope that I can live up to everyone's expectations. Thank you to Todd for the invitation to contribute.
Here is a brief description of my APRS gateway/digipeater station configuration:
I will start away from the radio-frequency side, the Internet connection. I use a DSL connection to the internet. Since bandwith requirements are very low, your family can still stream movies and surf the internet with your APRS gateway operating. Bandwidth requirements are so low that you could run an APRS gateway on an AREDN network connection or a D-Star data connection (both topics for another article) with plenty of bandwidth to spare. If you wanted to spend money on modems and copper telephone lines (remember them?) you could easily support an APRS gateway on a very low bandwidth 33.6kbps dial-up connection to the Internet. (Does any ISP support dial-up internet today?)
The computer I am using is an over a decade old quad-core computer that was given to me. It is running Ubuntu Linux, 64 bit Desktop version 21.10. This is much more computing power than what is required; a dual-core machine would be more than enough computing power for the task, and with modern operating systems is the minimum hardware required. Use whatever hardware and operating system you have; the software I am using will run on Windows just as well as it does on Ubuntu Linux. In fact, I have successfully run my station on an old RasberryPi, so if you have an old computer laying around chances are it will work for this application perfectly. The computer decodes and encodes packet audio using a software package called DireWolf. The software I use to actually digipeat and process packets to the APRS-IS network and also display stations on a map is YAAC. DireWolf has been rock-solid, and YAAC is very well supported by the user community and the developer, Andrew Pavlin KA2DDO. If you decide to use this software I would be happy to assist you.
A Screen capture of my Digipeater/Gateway in operation. The large gray window is YAAC showing other stations in the area. This is covering part of the window with the white background; this window is DireWolf and shows packets going to and from the radio.
Many people use fancy and expensive interfaces between their computers and radios. I use a very simple homebrew computer to radio interface. Transmitter keying is accomplished via a serial port on a USB to serial adapter. The DTR line in the serial port switches a transistor on to transmit. Audio from the speaker output on the computer to the microphone input on the radio is reduced by a simple resistor attenuator.
Computer to Radio interface and schematic.
The radio is a Yaesu FT-50 handheld; transmit power is set on high, which is about 5 watts. It is powered by the 12 volt output of the computer power supply. In the event of some sort of malfunction I can log into the computer remotely, shut down the computer and radio will also be shut down since it is powered from the computer. The radio is connected to a second hand Cushcraft 2 meter Ringo that is missing the lower set of radials. It is at about 20 feet up in the air on a PVC pipe that is attached to my deck with large hose clamps. The radio is connected to the antenna with about 40 feet of RG-8 coaxial cable.
Second-hand antenna on PVC pipe mast.
How everything is configured and how audio levels are set along with other details will be covered in future articles. I will also provide details about my mobile station at a later date.
--Dan Meyer / n0kfb
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