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SunSPOTs and ham radio

Posted by sean_sheedy on January 23, 2008 at 3:41 PM PST

This week I decided to drive from San Diego to Santa Clara to this week's MEDD conference rather than fly home and back again. This gave me the opportunity to try out a new ham radio product called the TinyTrak4 which is about to be released by its creator, Byon Garrabrant.

The TinyTrak4 provides me with an APRS setup in my car to track my position as I moved along. (I also beaconed that I could be reached by voice on 144.39 MHz, which is the ham radio national calling frequency for two meters, and kept a second radio on for that purpose.)


Present location

Ham stations near me

APRS users around the country

Now, there is a really cool product called the TinyTrak4 which has been through a year of beta testing (that's my TT4 on Byon's web page) and is about to go live. You hook up a GPS receiver to the TT4 and it creates packets and uses smart beaconing to send it into the ham radio APRS network via an attached ham radio.

The TT4 can do more than this, and one of the cool things about the TT4 is that it can take sensor data and attach it to these packets.

There are devices called "digipeaters" which hams set up to hear radios like mine, and retransmit them, the idea being that other radios in the area can more easily hear them. Transmissions can go over multiple hops or none at all depending on the path that the user sets in the tracker.

Furthermore, there are "i-gates" which are receivers hooked up to the Internet, which take packets (that are not flagged to not be gated) and post them to the Internet, where you can look at them on maps such as at the above links.

There are 30,000 or so APRS users out there, and a device that can include sensor data with a scheduled transmission is useful. This brings us to the other neat feature of the TT4, which is that it can be used as a data modem or "TNC" as it is known in ham radio speak.

APRS is not only used for tracking yourself (in fact, use of this mode with no other information is discouraged by some because it really does not contribute much other than a spot on a map, and does lead to more congestion of the channel.) Some other uses include letting people know how you can be contacted (as I did, by including the frequency I'd listen to), or send messages back and forth (many APRS systems are capable of messaging), or transmit weather station information, or many other uses.

What I wanted to put out there is that the SunSPOT is a device that is easily programmable using Java and has a number of interesting sensors that are of interest to hams, the original Makers. Temp sensor, accelerometer, inputs/outputs, etc. What could be done if you connect a highly programmable sensor like this to a network like APRS? What could you get from a network of sensors working simultaneously or that can receive and act on messages sent to it remotely?

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Interesting idea. There are lots of APRS weather and telemetry stations today (not to mention the more traditional APRS home/mobile stations). It's time for more Java in amateur radio in general though, especially mobile/embedded applications.

A portion of the 2.4gHz band is actually allocated primary(secondary) for amateur radio usage under Part 97 of FCC rules (US). Same with the 33 cm (902 MHz) band. This might allow US amateurs some flexibility operating under Part 97 with IEEE 802 technology at these frequencies; however, Part 15 devices like the SunSpot must tolerant interference from licensed ISM/amateur emissions and must not cause harmful interference.

Probably the most efficient network would be to a base station and then output to radio modem over RF or APRS I-gate via the Internet.

Thanks for the article... Mike

Good stuff, Sean.

As an aside, for those who may not know and who like to experiment with RF, check out the impressive allocation of spectrum you get to experiment with if you are an amateur radio operator in the US

The SunSPOT technology doesn't reside in any of these spectral ranges, it being in the ISM unlicensed portion of the band. But the two technologies are sort of spiritually related, which is why I mention it.