Data Radio Modems

Lately I've been thinking it would be cool to put a GPS transmitter
into a rocket for tracking purposes. I've found some really
lightweight and small GPS recievers out there, but I have not yet found
an inexpensive data transmission means. It seems that a quick and
dirty way to do this would be to hook up the RS-232 output of a GPS to
a data radio modem and then downlink the signal with another similar
unit on my computer. I do no thave my HAM lisence (yet), so that
limits some other avenues. Does anyone have any experience with this
or any good ideas? Thanks!
-Zach Bailey
Reply to
Loading thread data ...
Take a look at these.
formatting link
Reply to
Dave Grayvis
These folks might not meet the "inexpensive" criteria, but....
formatting link
Not a user, but have heard good things about their equipment.
Reply to
You can use commercially available RF modules, for example
formatting link
The lower power ones (~1mw output) do not explicity require a license as long you meet part15 guidelines. The problem with these is that at this low power level you are probably going to lose signal when the rocket lands at an appreciable distance (kind of defeats the purpose of GPS). However you should be able to get good signals during descent with a good directional antenna which will get you in the neighborhood, then you should be able to get a good ground signal.
Reply to
My students
formatting link
used a credit card sized Linux computer, GPS receiver, and a CompactFlash WiFi card.
formatting link
is working on transferring serial data.
Doug says that Ivan is working on putting a GPS receiver into their
formatting link
formatting link
looks interesting. More info about amateur radio and APRS tracking is at
formatting link
and many other places on the web.
Ramsey Electronics had/has a "Model Rocket Tracking Transmitter Kit"
formatting link
that will take an audio frequency telemetry source and modulate it. The MR6 isn't listed in their online catalog but I was able to call and order one as of a couple of months ago. They have kit and pre-built versions. I don't recall the exact price but the kit was around $30 or $40. Will
Zach wrote:
Reply to
Will Marchant
"Zach" wrote in news:
For a DIY method, it'd probably only take a single chip to convert the rs232 signal to FSK audio frequencies that you could feed into a low power 500mw CB radio walkie talkie.
On the ground, you could either run in into another chip to restore the digital data before running it into your laptop (if you want to view it with your own software), or even get the audio data fed into a soundcard with suitable software to do the decoding (if all you wanted was to view the data).
Its probably not the ideal solution, but cheap and possibly fun to experiment with. Maybe ask for more ideas in the amateur radio newsgroups. Some of those guys do a lot of this kind of experimentation.
Reply to
get your ticket :) It's not like it is hard.
Reply to
tater schuld
Check out:
formatting link
of RF modules, transmitters, receivers, transcievers
Reply to
Dan Major
If you're only looking to transmit location, consider APRS (automatic position reporting system). The basics are that a GPS outputs location through an intermediate device to a transmitter, which sends it via packet radio to your computer. All you really need to transmit is a GPS, a small 2m or 70cm transmitter (cheap on ebay), and something like this:
formatting link
I haven't used tinytrak, but people say it's really easy to use. It also is pretty inexpensive (your GPS unit alone would cost more than a cheap handheld transmitter and the tinytrack combined).
To receive the signal, all you need is a receiver (like a police scanner that picks up the frequency your xmitter transmits) and a computer with a sound card or terminal node controller (TNC). There's other things you can substitute for the computer, soundcard/TNC, and tinytrak, but the concept is the same.
Assuming you already have a GPS unit and a computer with a sound card (or a terminal node controller), the transmitter, scanner, and tinytrak combined will probably run you about $130 if you get the xmitter and scanner used.
Another option (if you can program microcontrollers, like the Basic Stamp) is to output the GPS data to a microcontroller, which creates an audio signal that's jacked into your transmitter. You can output Morse Code (CW), RTTY, AMTOR, or whatever floats your boat. There's freeware you can download that will decode it real time on your computer. This method also gives you the ability to transmit more than just GPS info (pressure, temperature, etc).
Hope that helps, Dave
Reply to

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.