The TRANSROC - a Retro Model Rocket Telemetry Transmitter

The TRANSROC Model Rocket Transmitter

The TRANSROC was a model rocket telemetry accessory designed by Estes Industries back in the early 1970s. The TRANSROC transmitted in the 27MHz Citizen Band frequency range, and could be built in several configurations, each designed to relay data from various types of sensors (audio, spin rate, temperature).

I owned the basic model back in the day. Over the course of many years and moves, I've managed to misplace everything except the main owner's manual.

Obviously we can do far better using modern technology, but I thought it would be cool to build one from scratch. So....

The goals of this project are:

Recreate the physical TRANSROC as close to the original as possible.
Use identical parts as much as possible.
Have some fun, and maybe learn something along the way.

The result is a functional, quite historically accurate recreation of the original transmitter, designed from photos of actual TRANSROCs, as well as from measurements and data from the original manual.

This Instructable guides you through building a TRANSROC in the Spin Rate Mode. In this mode, your walkie talkie will receive a tone varying in pitch depending on how much light hits a sensor. By analyzing the changing tone, you can figure out how fast your rocket is spinning while in flight.

Supplies

Since this is an electronics project, you'll need some basic tools:

Soldering Iron with a Fine tip (1mm will do nicely)
Rosin Core Solder
Water Soluble Flux
Desoldering braid
Narrow Pliers
Tuning Tools (hex, 0.1" and 0.078")
Thin CA Glue
10-32 Bottoming Tap
¼"-28 Bottoming Tap
Access to a 3D printer
Optional, an Analog Voltmeter or Oscilloscope

You'll also need all of the mechanical and electronic parts to build the transmitter. Most are still available, but some you must make yourself.

These parts can be ordered from Digikey.

(2) Capacitors, 0.01 uf ceramic disc (BC1078CT-ND)
(1) Capacitor, 3.3uf Tantalum (399-4556-ND)
(1) Capacitor, 33pf ceramic disc (445-180465-1-ND)
(4) Capacitors, 470pf ceramic disc (BC1021CT-ND)
(5) Diodes, 1N914 (1N914FS-ND)
(1) Resistor, 100k 1/4w, 10% (2019-CF1/4CT52R104JCT-ND)
(2) Resistor, 10k 1/4w, 5% (CF14JT10K0CT-ND)
(1) Resistor, 150k, 1/4w (S150KQCT-ND)
(3) Resistor, 270k 1/4w, 10% (CF14JT270KCT-ND)
(1) Resistor, 33k 1/4w, 10% (CF14JT33K0CT-ND)
(1) Resistor, 56 1/4w, 5% (S56QCT-ND)
(1) Resistor, 180 1/2w, 10% (CF12JT180RCT-ND)
(1) Transistor, 2N5138 PNP (2368-NTE159-ND)
(3) Transistors, 2N5172 NPN (2368-2N5172-ND)
(1) Transistor, 2N6027 PUJT (2368-NTE6402-ND)
(1) Type A23 Battery (N403-ND)
(1) CdS Photocell #5549 (PDV-P9005-1-ND)

You can order wire from Amazon. The magnet wire is critical and must be 30 gauge, but the 24 gauge wire can be any thin wire you have laying around.

Wire Kit, 24 gauge (Amazon), includes:
Wire, Red, 24 gauge, 2" long
Wire, Black, 24 gauge, 3" long
Wire, any color, 24 gauge, 30" long
Wire, Enameled Magnet, 30 gauge, 8' (Amazon)
A 10-32 3/16" Screw from an old computer case

The styrene and brass supplies can be ordered from Hobbylinc or Amazon:

Styrene Tube 9/32" dia. 2" long (Evergreen #229)
Styrene Tube 1/4" dia., 2" long (Evergreen #227)
Brass Strip 0.016 x 1/4", 4" long (K&S #8230)

Crystals for the 27MHz Citizen's Band are not readily available, and the only place I could find them was searching eBay. The cost should be less than $10 USD each.

Crystal, Channel 14 (27.125 MHz), or the channel/frequency of choice, HC-25/U Package

The iron slugs for the coils were really hard to find. I found only a single manufacturer, Micrometals. Unfortunately, they do not sell to individuals (See note at the end of this section).

Powdered Iron slug, 1/4" dia x 1/2" long (Micrometals TH48-0106F)
Powdered Iron slug, 3/16" dia x 5/16" long Micrometals TH35-0201)

You will have to make or buy the Printed Circuit Board (see the next Step).

These parts you will need to print on a 3D Printer:

Battery Holder
Bottom Transmitter Mount
Top Transmitter Mount
Thumb Transmitter Mount (Parts 1 & 2)

Put in the orders for the parts early so you'll have them ready for when your boards are finished.

Note: As the iron slugs and circuit board are the outliers, I have a very limited supply of each. Please contact me if you're interested.

Step 1: Buy or Make the Printed Circuit Board

The printed circuit board is the first thing you'll need. There are a few ways of getting the board. You can buy it from a board house, or you can make it yourself. The board itself is just under 1" x 2".

If you want to etch your own circuit board, there are several Instructables which walk you through the steps. I haven't tested any of the Instructables as I found it simpler to have someone else make the boards. Making your own board at home is a messy process.

The best way is to order the board is from a board house like JLCPCB. The Instructables editor does not yet permit individual Gerber files nor a ZIP file of all Gerbers to be attached. Here's how you can order your own boards:

Take the text files from this Step and download them to your PC.
Rename every file by removing the .txt extension. The result will be properly named Gerber files for the various parts of the board.
ZIP up the files into a single file. Name it Transroc_Gerbers.zip
Go to your favorite board house, upload the ZIP file, send them some money, and in a few weeks you'll have your very own boards!

Alternatively, you can get a pre-made ZIP file here:

https://github.com/d5aa962e/Transroc/blob/main/Gerbers/Transroc_Gerbers.zip

Download that ZIP, upload it to your favorite board house, send them some money, and you'll get your boards in a few weeks!

Step 2: Print the 3D Parts

The Battery Holder and three Mount pieces must be 3D printed. The parts were printed with PLA+ filament because that's the only filament I had in Black. PLA should be fine as well. A 0.4mm nozzle was used with a layer height of 0.12mm. Once the parts have been printed, test fit all the pieces and trim / clean up the parts as necessary.

Print these parts:

Battery_Holder-Main.stl
Bottom_Mount-Main.stl
Top_Mount-Main_v2.stl
Thumb_Mount-Part1_v2.stl
Thumb_Mount-Part2_v2.stl

Use your pliers to remove the support material from the Top and Bottom Mounts.

Glue the two Thumb_Mount parts together back to back, aligning the slots in both pieces.

Do NOT glue any other parts at this time!

Test fit the printed circuit board into the Top and Bottom mounts. The board should fit into the Top Mount and Bottom Mount parts very snugly. Carefully scrape the board (or more likely, the 3D printed part), until a complete, but snug fit is made.

Step 3: Building the Coils

The original TRANSROC kit supplied you with a printed circuit board that included the two coil forms glued to the board, and the coils were already wound and soldered in place. For the modern version, you'll have to cut the forms to size, cut (tap) the threads of the form, and then finally wind the coils. This isn't as hard as it sounds, but takes a bit of patience. Take your time to let glue dry and you should be able to build both coils over the course of two evenings (or a long day if you're ambitious).

The general process is:

Cut the threads (tap) into a piece of polystyrene tubing.
Cut the tubing to length.
Glue the tubing to the board.
Wind the coils around the tubing.

Since the original coils were pre-wound, I had to determine what size wire should be used. To do this, measurements were taken from photos and sizes scaled accordingly. The result was that 30 gauge wire was the correct fit.

Step 4: Tapping the Large Coil Form

The large coil form is made from a piece of polystyrene tubing (Evergreen #229 – 9/32” diameter). Don't cut the tube yet as you'll want some extra to hold onto.

Place a ¼”-28 NF bottoming tap into a variable speed drill (you can tap by hand, but it will take longer).
Hold the tubing in one hand, and with the drill in your other hand, place the tap up against the tubing and slowly start the drill.
Tap about 1/8” to ¼” and stop.
Reverse the drill and completely back out slowly. Clean the tap with a brush to dislodge the plastic shavings.
By hand, carefully thread the tubing back onto the tap. It's important that this step be done manually to ensure you don’t strip the threads you’ve previously cut. Once you’re sure the tap is on the existing threads, you may continue to tap the tube with the drill.
Repeat Steps 3-5 until you have reached the end of the tap.
Run the tap 2-3 more times up to the end of the tap, cleaning the tap and the inside of the tube each time. This will refine the threads.
Test fit the iron slug to make sure it can freely travel the length of the cut threads. Use your tuning tool for this. Do NOT force the slug. It will break (don't ask me how I know this!) If the slug can't travel the length of the threads without binding, repeat Step 7 until the slug moves freely through all threads.
Cut the threaded tube and test fit the slug one more time (you may need to run the tap through by hand to clean up the cut end of the tube. Mark the bottom of the coil form with a marker (you want to be sure the forms are placed on the circuit board in the correct orientation.
When you are satisfied with the threads, cut the tube to approximately 3/4" (19mm).

Step 5: Tapping the Small Coil Form

The small coil form is also made from a piece of polystyrene tubing (Evergreen #227 – 7/32” diameter). As with the large coil form, don't cut the tube yet as you'll want some extra to hold onto.

Place a 10-32 NF bottoming tap into a variable speed drill (you can tap by hand, but it will take longer).
Follow Steps 2-9 from Step 3.
When you are satisfied with the threads, cut the tube to approximately 5/8" (16mm).

Step 6: Mounting the Coil Foms

Test fit a coil form in the corresponding hole of the circuit board. The forms should fit very snug, but do not force the form into the hole. If the form still will not fit, gently file the hole. Alternatively, you can scrape the hole with an X-Acto knife a little at a time. You should not have to file/scrape much material from the board hole.

Position the forms on the board as shown in the diagram. Make sure the forms are perpendicular to the board from both the side and end views. One more time, test that the slugs can smoothly travel the length of the form before gluing.

Once you’re satisfied that the forms are square to the board, use a fine tip applicator to put a drop or two of CA glue around each form to make a fillet around the top side of the board. Make sure you don’t get glue on any component hole as you won’t be able to solder the corresponding part. If you do get glue where it shouldn’t be, use CA Remover on a cotton swab to clean the board.

Let the glue dry thoroughly.

Step 7: Preparing to Wind the Coils

Winding the coils is perhaps the hardest part of this project. You have to be careful not to kink the wire, and holding the windings in place is tricky with just two hands. In short, use a method that works best for you.

Use the 30 gauge magnet wire to wind the coils.

These conventions are used in the next few steps to help guide you in winding the coils.

up, feed wire up Feed the wire starting from the bottom of the board up through the hole to the board top.

down, feed wire down Feed the wire starting from the top of the board down through to the board bottom.

When soldering the coil wire to the circuit board, be very aware

of where the soldering iron is.

It is very easy for the iron to touch the styrene forms and melt them.

Refer to the two photos of this Step when winding the coils per the steps below.

Step 8: Winding the Top of the Large Coil

Cut a 40” piece of wire for the large coil. Scrape 1/8” of insulation at the 9” mark. Thread the wire down through Hole #1 so that there is nine inches of wire below the board. Solder the wire into Hole #1.
Wind 22 full turns plus an additional 1/3 turn counterclockwise on the top of the form. Wind 3-4 turns at a time, sliding the turns tight against each other as you go. Secure the remaining wire along the tab at the end of the board (do not thread the wire through the final hole just yet. Run thinned white glue along the coil to secure the winding in place. Let the glue dry.
Now thread the loose end of the wire up through Hole #3. Scrape the insulation off with a knife and solder it in place. Congratulations, you’ve completed the first of FOUR windings!

Step 9: Winding the Bottom of the Large Coil

Wind the lose 9" wire counterclockwise around the bottom of the form. Wind four full plus ¼" turn and feed the wire up through Hole #4. Again, be careful not to kink the wire.
Scrape the insulation from the wire around Hole #4 and solder in place. Pass the loose end down through Hole #5 and cut to 1/8". Again, scrape insulation from the wire and solder it to Hole #5.
Test the continuity of the solder connections for both coils. If there isn't any continuity for a coil, the most likely cause is not enough insulation was removed.

Step 10: Winding the Small Coil

For the smaller coil, you will need to make two separate windings. Both windings are wound on the top side of the board. Cut at least 20” of magnet wire for the inner winding and 15" for the outer. Following the above procedure, first wind the inner coil, then the outer coil, noting direction.

Feed the 20" wire down through Hole #6. Solder in place.
Wind 12 ¾ turns clockwise; wrap the loose end around the board and add thinned white glue to hold the windings in place. When dry, feed the loose end down through Hole #7 and solder in place.
Feed the 15" wire down into Hole #8 and solder in place.
Wind 4 ¼ turns counterclockwise; again, wrap the loose end and add glue. When dry, feed the loose end down through Hole #9 and solder in place.

Congratulations!!

Your board should look like the attached photos. In 1972, Estes would sell you a board, with all the work you just put in to make your own, for just $4.00 USD! You probably wish they still would!

Step 11: The Battery Contacts

The TRANSROC kit included battery clips bent into the correct shape. For this recreation, you'll have to bend a brass strip into the proper shape yourself. In addition, depending on how authentic you want to get, you may wish to "build" an authentic Eveready 504 battery.

The battery contacts are made from 0.016" x ¼" brass strips.

Follow the next set of photos to bend the brass strip into the correct form. It's important to hold the brass firmly against the plastic parts to help keep the bends clean.

Position the brass strip on the bottom of the battery holder so that the end about lines up with the cutout.
Hold the strip against the battery holder and line it up with the tab.
Bend the brass strip up against the tab so that the bend forms a right angle.
Fold the strip over the top of the battery holder.
Place the Top Mount over the brass strip / battery holder assembly. While holding the parts together, place a small screwdriver up against the space between the holder and brass.
While holding the screwdriver firmly, bend the brass strip up against the Top Mount so as to get a clean bend.
Use your fingers to complete the bend.
You should now have something that looks like this photo.
Make the first bend with a pair of pliers, making sure the pliers are perpendicular to the long edge of the brass strip.
Repeat for the second bend.
Now cut the brass strip to length and you will be done!

You can print out the below PDF so you have a life size template to compare to.

Battery_Clip_Template.pdf
Download

Step 12: Assembling the Battery Box

Solder the Red and Black wires to the respective battery clips first. Be sure to orient the wires properly as shown in the photos.

Press fit the clip with the Red wire through the Top Mount.

Press fit the clip with the Black wire through the Thumb Mount

Test fit the Top and Thumb Mounts in the Battery Holder. You may need to clean up some of the leftover PLA in order for the parts to fit properly. Once you're satisfied with the fit, use CA glue to fasten the parts together. Use a rubber band to hold the parts in place until the glue dries.

Step 13: Making an "Authentic" Battery

"Real" 504 batteries aren't available any longer. There are generic 504 batteries on Amazon, but they are round where the originals were square with rounded corners. Since this is a retro project, you'll want to make your battery look like the real thing. You can use a 504 battery, but it won't look right, and besides, they are $10-$12 a piece!

The best option for powering the TRANSROC is with an A23 battery (12 volts). While no field strength tests were done, the A23 seemed to perform on par with the 504. The A23 is also much cheaper, and three grams lighter.

Print the two A23 STL files:

Battery_Carrier-A23_v2-Cover.stl
Battery_Carrier-A23_v2-Main.stl

Put a drop of CA glue into one of the holes in the Main part of the battery carrier. Take a scrap piece of wire from one of the components and place it in the hole. Repeat for the other three holes. Once the glue has dried, cut the "pins" to length and test fit the cover.

Place an A23 battery into the carrier with the positive end through the larger hole at the thin end of the carrier. Thread a 6-32 through the other end to secure the battery in place. The screw is standard desktop computer screw – you should have many laying around! Any similar screw should work, but ideally it should be a 3/16" long 6-32 screw with a flat, rounded head.

Test fit your new battery in the TRANSROC battery holder.

Finally print out the Battery Wrapper v2.pdf on a color printer. Print this PDF at 50%. Cut on the lines, wrap it around the battery holder and glue the overlapping paper together. This will make an authentic looking wrapper for the battery carrier. The wrapper can slide on and off for when you need to replace the A23 battery.

Now you have yourself an "authentic" Eveready Union Carbide 504 battery! Just make sure the + / - signs of the wrapper match up with the + / - of the actual battery.

Step 14: Populating the Circuit Board - Modulator

The assembly order is a bit different than the original manual so as to allow for testing of the Modulator section prior to moving on to the rest of the parts. Use a fine tip soldering iron. A 40-watt iron should be perfect.

Please be careful when soldering so as to not let the hot iron touch the coil forms. As they are plastic, the hot iron will quickly make a mess if the iron gets too close.

Only two components differentiate the Spin Rate from the Rocket Finder modes, R5 and C7.

Rocket Finder Mode: R5 (270k Resistor), C7 (3.3µf Capacitor)

Spin Rate Mode: R5 (CdS Photocell), C7 (0.047µf Capacitor)

While the fixed value components of the Rocket Finder Mode provide a stable pulse approximately once every 600ms, the varying light hitting the photocell modulates the pitch of the tone which can then be used to measure how fast the rocket is spinning.

While this project built out the TRANSROC in the Spin Rate Mode, you are free to assemble your TRANSROC in any configuration.

For a more in-depth discussion on the various modes, please see the individual telemetry manuals found on Transroc.org.

Place and solder the parts to build the Modulator.

Install diode D5, orient properly!
Install resistor R4 (100k, brown, black, yellow)
Install diodes D3 and D2, orient properly!
Install resistor R1 (270k, red, violet, yellow)
Install diodes D1 and D4, orient properly!
Install capacitors C10 and C6 (470pf)
Install transistor Q1, 2N6027, orient properly!
Install transistor Q3, 2N5172, orient properly!
Install resistor R2 (270k, red, violet, yellow)
Install resistor R3 (10k, brown, black, orange)
Install Jumpers J3 and J1 (see Note #1)
Install capacitor C4 (470pf)
Install resistor R6 (150k, brown, green, yellow) - leave loop to free end lead
Install resistor R7 (10k, brown, black, orange)

Note #1: For jumpers J1 & J3, cut small pieces of insulation (as done with the photocell), and solder carefully so you don't melt the coil forms.

Although this Instructable is for the Spin Rate Mode, you can opt to build your TRANSROC in the Rocket Finder Mode. Follow the appropriate section below based on which mode you chose.

Parts Specific to the Spin Rate Mode

For the photocell, strip off two short pieces of insulation from the leftover wire and slip the insulation over the leads of the photocell. You want just enough of the photocell wires to be exposed to give you enough to solder. Solder the photocell to the holes marked for R5.

Install a 0.047uf capacitor at the position marked C7.

Parts Specific to the Rocket Finder Mode

Install a 270k (red, violet, yellow) in the position marked R5.

Install a 3.3uf capacitor in the position marked C7. Be careful of this capacitor! It has a polarity! The capacitor may be marked with a plus sign, or it may have a band indicating the negative lead.

Solder temporary battery leads to the (+) and (-) points (see the Notes of "Board_Silk" photo).

Clean the board with water or isopropyl alcohol. This is important! The Modulator will not work properly until the board is cleaned thoroughly.

Step 15: Testing the Modulator

The idea behind testing the Modulator at this point is to prevent any issues with the RF Section interfering with the workings of the Modulator.

If you built your TRANSROC in the Rocket Finder Mode, the Modulator pulses the transmitter about once a second. The voltage difference is small, only about 0.6v (which agrees with the original TRANSROC manual). In the "Waveform - Rocket Finder Mode" photo, the ΔY is referenced to the top (15v) trace. The oscilloscope probe was placed at the "top" of R3 (10k).

Hook up the test leads and then connect the battery temporarily. You should see pulses on your test meter. If you use a digital meter the pulses will be difficult to interpret. An oscilloscope or analog voltmeter will be better.

As the Modulator's frequency increases, as in the Spin-Rate Mode, the waveform becomes less "square".

If the Modulator is working, continue with the next section to assemble the RF Section. If you are not seeing waveforms similar to the above photos, doublecheck your soldering. Check for loose connections and for components inserted incorrectly. Diodes and transistors are easy to insert backwards. Also, be sure to clean the board! Tests have proven that a board covered in flux will not work!

See the last step (Troubleshooting) if your TRANSROC is still not working properly.

Step 16: Populating the Circuit Board - RF Section

Now we're add the parts for the RF Section:

Install transistor Q5, 2N5172, orient properly!
Install resistor R9 (56 ohms, green, blue, black)
Install capacitor C2 (0.01uf)
Install transistor Q4, 2N5138, orient properly!
Install capacitor C1 (470pf)
Install resistor R8 (33k, orange, orange, orange)
Install transistor Q6, 2N5172, orient properly!
Install capacitor C5 (33pf)
Install capacitor C3 (0.01uf)
Install Crystal X1 (your choice of frequency)
Install the Antenna wire in the hole marked AE1

Again, clean the board!

Thread an iron slug into each of the coil forms. From previous steps, the slugs should thread easily. If they don't, do not force or they will crack!

Step 17: Final Assembly

When satisfied your TRANSROC is working, unsolder the test wires from the (+) and (-) holes.

Fit the circuit board into the Top and Bottom Mounts.

Cut the Red and Black wires from the battery carrier to length, leaving some slack (see photo), and solder the wires to the (+) and (-) holes.

Congratulations! You've finished your TRANSROC! Time for Final Testing!

Step 18: Testing Your Transmitter

This is the part where you tune your TRANSROC so that it performs the best it can!

Turn on your walkie talkie and set it to mid-volume. Install the battery into your TRANSROC, observing the polarity. You should hear a tone on your walkie talkie that varies in pitch depending on how much light hits the photocell.

Turning the Oscillator (small) Coil

Insert the small tuning tool into the small slug from the bottom of the board. Rotate the slug counter clockwise slowly until the tone stops completely. Once you've found this spot, turn the slug about 1 1/2 turns clockwise. This should give you the best oscillator stability.

Note: The TRANSROC manual states that the correct place for the small slug is 1/8+ to 3/16" from the bottom of the coil form. Since we are not using the exact same parts as the original, this distance cannot be verified. The best way to verify the "correct" spot is to follow the above procedure for best stability.

Tuning the Antenna (large) Coil

Tuning the antenna coil is a little more complicated. This is due to your body and other surroundings effect how well the antenna is "matched" to the TRANSROC.

Turn on your walkie talkie ("radio") and set the volume to a level where you can hear it well.
Collapse the antenna and wrap the radio first in a cloth (for insulation), and then in aluminum foil to shield it from the TRANSROC. Place the radio a few feet from where your TRANSROC will be, but not so far that you can't hear it.
Hang your TRANSROC from a piece of string attached to the free end of the antenna. This will help isolate your TRANSROC from the surroundings.
Install the battery. You should not hear any tone on your radio. If you do, wrap the radio with more aluminum foil. Once you can't hear the tone any longer, slowly unwrap the foil until you just start hearing the tone again.
While keeping your hand as far from the TRANSROC as possible, use the 0.1" tuning tool to tune the Antenna Coil slug. Turn the slug counter clockwise until the tone on your radio is the strongest. If the tone strength is overwhelming, add more foil to your radio.
As you turn the slug, you'll hear the strength of the tone get weaker and stronger. By alternating the rotation of the slug, and the addition and removal of aluminum foil, you'll be able to get the strongest signal from your TRANSROC!

At this point, your TRANSROC is tuned -- almost...

The above is what's called "bench tuning", and is a perfectly valid procedure. However, remember the comments above about surroundings? Once you put your TRANSROC into a model rocket, you may need to "retune" the antenna coil for maximum signal. Don't worry, you can still follow the above procedure, but if you have a friend, your friend can take the place of the aluminum foil by walking further or closer to your rocket-mounted TRANSROC. The effect of adding and removing foil is replaced by moving closer and further from the TRANSROC.

You are now ready to fly your TRANSROC! Enjoy!

Step 19: Conclusion

At this point you should have a fully working TRANSROC (if not, continue to the next step).

The only remaining thing is to fly your TRANSROC and analyze the data. Although the technology is old, we have better ways of analyzing the data these days.

Analyzing Data "Back in the Day"

When the TRANSROC first came out in the early 1970's, technology wasn't nearly as advanced as it is today. You would have had to lug a tape recorder to your launch site to record the output from the speaker of your walkie talkie (hopefully you would have had a portable tape recorder). You could then listen to the sounds (if launching a TRANSROC in Microphone Mode), or feed the audio to a Paper Tape printer and then "measure" distances to see how fast your rocket had been spinning (Spin Rate Mode), or determine temperature from the printout (Temperature Mode). The possibilities were "fascinating."

Analyzing Data Today

Today we have so many more options! You can easily record the output of your walkie talkie by using the Record feature of your Smartphone. At that point you'd automatically have a digital copy of your telemetry. You could transfer the audio file to your laptop and then open it with a tool like Audacity. You could then do similar "measurements" of the peaks and valleys to determine spin rate and temperature. You could even go so far as writing your own custom computer program to specifically analyze the type of data coming from your TRANSROC! A future Instructable will go over the interpreting the results of actual flights of a TRANSROC. Stay tuned!

The possibilities are almost endless!

Hopefully you had fun building this replica of a piece of model rocket history!

Thanks for reading!

Safe flying!

As with the Gerber files, there are some file types that are not yet supported in the Instructables editor. All files used to create this project, including the original KiCad files can be found on GitHub at:

https://github.com/d5aa962e/Transroc

Step 20: Troubleshooting

Hopefully you won't need this step, but as with any kit, there could be issues which prevent the TRANSROC from working properly. Let's look at a few.

Make sure all diodes are positioned correctly. This means the banded end of the diode should face the direction of the arrow in the the picture.
Make sure the transistors are in the proper places. The 2N6027 and 2N5172 transistors look alike.
Recheck the resistors to make sure the values are correct. Sometimes the color bands are hard to see. A bright light can help see the bands clearly. The orientation of the resistors doesn't matter, but the values do! This goes for the capacitors too.
Be sure your walkie talkie is set to the same channel (frequency) as your TRANSROC's crystal.
Measure your battery. It should be around 12 volts. Also make sure the battery is inserted properly. The TRANSROC has a protection circuit (diode D1) which prevents the TRANSROC from operating if the battery is installed backwards.
Reclean the board with isopropyl alcohol. Having a dirty board is like having shorted connections, and could prevent your TRANSROC from working properly or at all.
Check for solder "bridges". This is solder in places where it shouldn't be. The photo for this step shows a solder bridge before and after. To remove a solder bridge:
Clamp the circuit board so it won't move.
Add flux to your desolder braid. This will help the braid wick up the molten solder.
Place the braid over the solder bridge. Put your soldering iron on top of the braid, pressing down firmly. Once the braid gets hot enough, you'll see the molten solder wick up into the braid.
Remove the soldering iron and braid and inspect where the "bridge" was.
Clean the board.
Solder the original connections, being extra careful to not create another solder "bridge".

If you have trouble soldering without creating "bridges", a smaller tip on your soldering iron may help.