APRS Beaconing: On Being Relatively Prime

I ran into an amusing situation on a recent family bike ride with our GPS-to-APRS trackers running: my ladies were transmitting a few seconds apart. As a result, I had to listen to a pair of very short data bursts in quick succession throughout the whole ride.

Under normal circumstances that doesn’t happen, because I set the TinyTrak3+ trackers to delay during and wait a second after a voice PTT that collides with an automatic beacon. Somehow they never managed to delay an APRS beacon to knock the synchronization off kilter.

So I tweaked the automatic transmission intervals to make us relatively prime: 179, 181, and 191 seconds. That’s close enough to the original 180 seconds as to make no difference, while now ensuring that we won’t collide with each other for very long even if we should get aligned.

An alternative is SmartBeaconing, which I’ll turn on in a while after I collect a bit more data.

A useful table of primes is there.

If you have some spare CPU and power, you can join the Great Internet Mersenne Prime Search and help find new primes, albeit ones much larger than I need…

5 thoughts on “APRS Beaconing: On Being Relatively Prime

    1. Brood II is scheduled for 2013 and, from what we remember of the last time we were around when a brood emerged, it’s a wonder to behold.

      I suppose the cicadas we hear now are either early adopters or aperiodic. They’re buzzing in the trees every evening these days… wow are those things loud!

  1. Ya know the song by Queen “We will rock you”? ( http://www.youtube.com/watch?v=-tJYN-eG1zk ) Guitarist Brian May, astrophysicist, recorded the “stomp stomp clap” section just once and dubbed it in bunches of times. He constructed the stomp delays based on a series of distances based on prime numbers to make it sound like a true crowd of people; not just one in an echo chamber.

    http://www.npr.org/templates/story/story.php?storyId=128935865

    – Steven Ciciora

    1. Ya learn something new every day around here… our young lady was impressed to hear that rockers aren’t always dopes.

      Thanks!

      1. Singer/lead guitarist of The Offspring has a PhD in microbiology, and Thomas Dolby has several degrees and has worked as a programmer for Apple for many many years. I used to know several more but can’t remember any right now. Several recording engineers that have had somewhat successful careers have EE’s, too, most notably Steve Albini. You are unlikely to have heard his music, but anyone who has ever listened to a radio has heard stuff he’s produced and engineered.

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