OLD DESIGN 
433mhz Tracking Transmitter

The following information is for the OLD design and is included for those possessing the old transmitter modules..

My old tracking transmitter board was originally is based on the circuit designed by Stewart Lilley and described at http://www.dars.org/Shroudlines/MA_2001.pdf   Total cost for the transmitter and the receiver circuits is a little over $26.00 each.  They used the old Velleman TX433 receiver module and the Velleman RX433 receiver module which are available which were available thru Radio Shack for about $10.00 each.  The two advantages of this design are low cost and one-sided boards which make alignment of traces on 2 sides for hole allignment un-necessary.  This allows you to more easily fabricate the circuit boards at home.

Circuitboard Parts Layout

The transmitter module is soldered then bent over the labeled portion of the circuit board so that it will not be damaged during repeated insertions into the rocket airframe.   The circuit board may be cut off near the dotted line if no piezo beeper is desired.   There are 4 jumpers marked in colored dotted lines.  INSULATED wire should be used for the 2 jumpers near R2 and R1.  The holes are drilled for 1/8 watt resistors except for R1 and R2 which are difficult to find in 1/8 watt.  I found use of a 9v battery to be desirable.  The 12v batteries just don't have much current supplying capacity or life by comparison.  Note that a 150 k resistor is used for R6 to allow the transmitter to operate correctly in cold weather down to 8 volts.  (With a 100 k resistor it will generate a steady tone under those conditions.)

view from top (component side) of circuit board

Click on the image to download the transmitter circuit board photo-etching mask.  You'll need to size the image for printing so that the IC pins line up exactly with the holes for your printer.  I use about 590 dots per inch.  You can etch 7 complete transmitter boards and 2 without the piezo on one 6" x 6" board. 

Getting It To Work

Rubbing alcohol (91%) may be useful remove the flux but I find that a spray can of flux remover works better.  You might wish to use your finger to cover the hole on the piezo when de-fluxing.  Rub off the remaining film with Scott Towel and let the board completely dry. (A hair drier will dry the board in seconds.)   Holding the antenna or moving it near the components will shift the frequency of the audio tone or beeps.  This is normal.  (Initially, I found that the board may not work properly while it is cold and wet with flux remover.  The usual symptom was very fast beeps or a steady tone.  This was cured by changing resistor values.)

The following is an introduction to circuit board production.  For drilling circuit boards, a 1/32" drill bit, Dremel Tool (with chuck), and magnifier are used.