Some sort of tracking is a must where I fly.  While our Brothers, Oregon site is a large wide open space,  the sage brush covers the ground for miles and creates a 12-40"" blanket for rockets to hide under.  Even if you are twenty feet  away, it can be difficult to locate your rocket.  There are several commercially available locator beacons on the market today  including Walston, RocketHunter, Adept and  GPSFlight.  They are all fairly expensive and have some unique characteristics.  Size, range, and battery life are perhaps the most relevant.  GPSFlight will even transmit back the Latitude/Longitude of your rocket!  All of these, however, are relatively expensive.  The transmitters will set you back at least $100, and the receivers more than $200.  If you already have a ham license, an HT capable of receiving in the 2m, 70cm, or 900 Mhz band, then you can build a simple locater beacon for less than $40 that will let you track your rocket to at least 10,000'!  You can even build something that will give you GPS coordinates for less than $150!

Take a look at my LATEST radio beacon project!

I've got two transmitters that I've been using with much success.  The first is based on Programmin' by Pete's excellent web-site,  and operates in the 70cm ham band.  The transmitter module looks just like the picture on the left.  I bought my first transmitter from Lemos International, but found them to be difficult to deal with.  I've bought other transmitters from Abacom Technology in Canada.  I highly recommend them.  I also believe you can order a similar modules from Linx via Digikey (part number TXM-433RM, .pdf manual), but they appear to have a much lower output power.  I'm not sure that's necessarily true, since all of the modules I've ordered look identical.  Even the specs sheets have been derived from the same source.

  I've also had some success with similar 900 Mhz transmitters.  These have a 8 selectable output frequencies.  The Linx part number is TXM-900-HP-II.  Here's the .pdf manual.  I've used the same PIC (here's the .asm file) to drive both of these transmitters.

My other transmitter is an Alinco DJ-4C that I picked up on Ebay for $50. I run it in two configurations.  The first uses the same PIC that is used to drive the transmitter mentioned above.  I've wired it directly to the Alinco with three wires; Power, Ground, and Audio input.  The audio input also serves as the PTT input.  Here's some more details on the construction of that project

The second configuration uses the same transmitter, but instead of transmitting audio, it transmits APRS packets.  The APRS packet contains GPS coordinates captured by the on-board oem GPS module.  The ascii-strings from the GPS are turned into AX.25 packet via a Tiny Track board available here.  The PIC on the Tiny-Track was reprogrammed with code from the SOTT project.  This was necessary to invert the input to the Tiny Track from the GPS;  the GPS outputs TTL level ascii strings, but the Tiny Track expects RS232 levels.  Instead of adding a level shifter/inverter, I just modified the software to expect inverted levels.

Here's a picture of the whole the whole mess, designed to fit into a 54mm PML nose cone.  Starting from the left you see the GPS module (pdf manual), then a 9-volt battery.  The battery powers the Tiny Track directly.  Power for the GPS is pulled off of the 9V regulator on the Tiny Track board. Next is the transmitter, which contains it's own battery.

This board works just fine 'in the lab', but I've never actually been able to make it work in the field.  For some reason, the receiver has failed to lock, and I've had to resort to good ol' RDF techniques to locate the transmitter. 

For a receiver, I'm using my VX-5R handheld transceiver, a yagi antenna, and a home-made packet decoder.  The packet decoder consists of an MX614 decoder chip, an LCD display, and a PIC to decode the x.25 packets and drive the LCD display.

I just found a really cool board which integrate a transmitter module with the 1200bd modem.  It's limited to transmitting at 144Mhz, but looks promising.

blacksky Altacc ALTIMETERS

I'm constantly searching for the mounting hole pattern for the blacksky 2A. 

For whatever reason, I frequently find myself replacing the LED on my Altacc.  I'm sure there are others that will fit, but I find that this LED works just fine:  Digikey Part Number L62911CT-ND.


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