Our networked world Archives

Packet and SFWEM interconnects

28 May, 2021 by sky 1 Comment

Over the last year (most of 2020), the majority of my radio work has been focused on making my connections between packet radio and SFWEM even more resilient.

SFWEM.NET is the San Francisco Wireless Emergency Net, which is a mesh network that’s being built out by amateur radio operators with the intention of being a communications backup in time of emergency — when phone and data networks may be locally overwhelmed or not functional. Beside that, however, it’s an interesting experiment for amateur radio operators seeking to understand the benefits and limitations of “wi-fi” as a long-distance tool. [Read more…]

Visualizing packet traffic

26 April, 2020 by sky Leave a Comment

Very techie here… For a few months I’ve been operating a packet radio station on a 2-meter radio frequency here in the San Francisco Bay Area. I explored what it would take to make this a full “BBS” (like an online “forum”), and then backed off and let it just hang around n this frequency listening to the other (mostly BBS) stations. A few days ago, I got interested in graphing the data to better understand what stations were using the frequency and when.

Packet radio was very popular 20 to 30 years ago, and has mostly been displaced by other amateur radio digital technology and by the Internet. Yet, it’s still quite reliable and is a good way to pass messages from one place to another when Internet or voice communications are unavailable (i.e. in an emergency). I’ve always been interested in the presentation of data, and it was an interesting challenge to figure out how to chart the data in ways that support inquiry.The result of my experimentation is visible in a chart.

The chart is made by this process:

JNOS (the software that runs the packet radio station) logs all data it hears on the radio;
A Python script analyzes this log file, keeping track of what stations were heard in each hour;
The Python creates javascript data in a form acceptable to Google Charts;
The javascript is transferred to a web server;
PHP code reads the javascript and inserts it in an HTML page;
Google Charts javascript fashions the data into the interactive chart.

A “cron” job carries out this process once each hour to keep the chart data current. Because each data bucket spans a whole hour, there’s no need to update more than once an hour.

Packet Radio Notes

25 February, 2020 by sky Leave a Comment

In amateur radio circles there’s much use of digital modes to exchange information. (In olden days it was almost exclusively limited to “chatting” on the air.) At least in the circles I’m running in these days this is true. “Packet radio” involves putting a computer on the front end, which then controls the radio, connecting to other packet radio stations and transferring messages digitally. At the lowest level the software has a command-line interface (accessed via radio), and at its highest level, it is basically supporting programs that exchange email (again, by radio, not thru the Internet).

Later articles:
° Packet and SFWEM Interconnects
° Visualizing Packet Traffic

My packet radio station operates on 145.07 or 145.09 mHz (also known as “2 meters” and mail is exchanged by “connecting to” AA6AX-1 via that radio. If you need to email me about this, please use the email address packet@aa6ax.us.

The station uses a Raspberry Pi 4 as the computer, and I use VNC to view the virtual “screen” of the RasPi and interact with the system. The radio is a cheap 2-meter transceiver, and a circuit board in a box called a “TNC” attaches to the computer and controls the radio. The photo shows the RasPi (about 4 inches wide) on top of the slightly-larger TNC. Plug it all into electrical power, add a radio with an antenna, and it’s on the air.

(More aa6ax info.)

This diagram shows the components of the packet station. Most notable are the Raspberry Pi computer (the “RasPi”), with the reddish TNC-Pi on the top, connecting it to the radio. The radio has an antenna, and is connected to a power source.

The computer itself is on the local network, and the VNC software lets me view its “screen” on my own computer, and use my mouse and keyboard as if they were directly connected to the RasPi computer. It’s kind of a virtual computer.

When did you stop answering your phone?

12 April, 2019 by sky Leave a Comment

Yesterday I had to answer my phone.

Does that sound odd? First of all, what’s a phone for if you don’t answer it? But second, who answers the phone any more, given the overwhelming volume of spam calls we receive every day?

You’re probably thinking “Why is he even asking this? When was the last time I answered a phone call?”

[Read more…]

Olympic-size Backup

21 January, 2018 by sky Leave a Comment

The San Francisco Bay Area comprises many cities, two of which, Oakland and San Jose, are larger than San Francisco itself. San Francisco has a rapid-transit system whose central backbone is a half dozen routes on which light-rail-vehicles [LRVs] ply the streets and a single-track (in each direction) subway under Market Street. The subway is called the MUNI Metro. [Read more…]