Tracking Transmitters

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Well-Known Member
Jul 31, 2011
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Has anyone else noticed the radio tracking transmitters and/or the model rocket locator kits available from JBGizmo?

What did you think? I have used some of Jerry's techniques and designs over the years that are similar to these. I could make the circuits from what he has posted about them on his website, but at a cost greater than the cost of the kits.

Bruce S. Levison, NAR #69055

Never heard of him, and this is neat stuff!

I really like the 108MHZ FM transmiiter/receiver pair. The schematics for the sonic locators are also cool

Thanks for the tip!
I got my kits from JBGizmo today they look great! The transmitter units even came with batteries. All the parts were labeled and neatly arranged on a sheet of paper.

Bruce S. Levison, NAR #69055
Keep us updated on how well they work. I'm planning a 2+ mile flight for late summer and am looking into the tracking transmitters as well.

I built the AM/FM/SW receiver in about three hours yesterday. Haven't tested it yet. It was a nice kit to build with only a few minor issues so far.

Bruce S. Levison, NAR #69055
I built the larger tracking transmitter (FM108K) from JBGizmo yesterday (in about 2 hours time) and tested it with the receiver that I assembled before. Both parts worked as stated, again only some minor assembly issues for the kit. Overall these are excellent kits, inexpensive, fun to build and they work the first time! I can hardly wait to test these units out in a rocket. I will post some pictures and more detail later.

Bruce S. Levison, NAR #69055
Do the tracking transmitters tell you which direction the rocket is after it landed?
The signal strength of the tracking transmitter is used to home in on its location. There are several volume controls on the receiver that are adjusted to give a low to moderate signal. The receiver is held up aginst your body which effectively shields the signal from behind you. As you turn the signal gets stronger when you are facing in the direction of the transmitter. I hope to field test these soon, see attached picture of my completed assemblies.

Bruce S. Levison, NAR #69055
These are nice kits, they both worked the first time I put the batteries in the completed assembly. The transmitter (which was more challenging to assemble because of its small size) even included two batteries! The parts are nicely laid out, labled and taped to a sheet of paper, see the picture of the smaller transmitter (which I hope to build soon) attached.

Bruce S. Levison, NAR #69055
I built the smaller transmitter last night (FM108KS) from JBGizmo in about 3 hours time and tested it with the receiver that I assembled before. The smaller transmitter (like the larger one) worked the first time I powered it up. I had no issues with the assembly of this kit. These three are all excellent electronics kits, inexpensive, fun to build and with a little care they work the first time!

I will post some pictures later.

Bruce S. Levison, NAR #69055
Let me know how the work in a flight situation! You have got me really interested now!

Hey, how much did those kits cost. I did go to their website, but only found prices for individual parts, not kits.
The receiver was $30.00 and the transmitters were $15.00 each.
For prices download the order form that you have to mail in at:

The smaller transmitter (FM108KS) weighs in at 12 grams with the 12 Volt battery installed and the larger transmitter (FM108K)weighs just under 15 grams with the 12 Volt battery. For camparison and empyy standard (A-C) motor casing weighs around 11 grams.

Attached is a picture of all three kits that I assembled.

Bruce S. Levison, NAR #69055
Here is a picture of the bottom side of the smaller transmitter unit showing the surface mounted components.

Bruce S. Levison, NAR #69055
jbgizmo cautions on his website that the small transmitter takes a bit of soldering skill given the compactness of the circuit board.

Was that a fair assement for the novice solderer? (namely myself)?

I was worried about assembling this small transmitter kit too since other surface mount kits required two or three rebuilds to get them right.

If you follow the "Tin and Tack" method mentioned in the instructions at the JBGizmo site you should have no problems assembling the smaller kit. Only the IC on the smaller transmitter is surface mounted and I didn't find it nearly as difficult to solder as other surface mount kits I attempted to build. That said I did assemble this kit using a magnifying glass( ) and a soldering iron with a very small and sharp point (Ungar Micro Spade tip):

I have assembled about 30 electronics kits and these are by far the best I have seen! The parts are neatly laid out and labled, the directions are good and are easy to follow, and the kits work the first time with minimal tweaking!

If you need practice at soldering I suggest you build the receiver first. That's what I did to get back into practice with soldering.

Bruce S. Levison, NAR #69055
Very interesting... My dad is an enviormental consultant, and he has these long range transmitters that he puts on turtles to track them... You can guess our plans to adapt surplus into rocketry transmitters:D

Let me know how this works.... If the turtle transmitter idea doesent work, this would be another interesting thing to look into!

This thing is small.

Went to the local RS to get an appropriate soldering iron. I saw the soldering braid and foolishly decided that I wouldn't need it.

Several solder bridges later...

Well, mabey I will finish this little project tonight.

The most difficult part is the IC.
construction of the transmitter tonight and ...

no luck

Hope I didn't fry the IC with the hot iron.

How much abuse can these things handle? Double EE's?

You probably didn't fry the chip. Counterintuitively, the least stress is put on the chip by using a powerful soldering iron and working quickly, so the chip doesn't have time to heat up. Trying to use an underpowered iron actually causes more damage. I've been known to use a large chisel tip, especially when there is a lot of copper. My bench has two temperature controlled irons, so I don't have to swap tips.

A technique that works well is to solder it in quickly, not worrying about solder bridges. Then go back with the solder wick and remove all the solder bridges.
Originally posted by Stewart32
construction of the transmitter tonight and ...

no luck

Hope I didn't fry the IC with the hot iron.

How much abuse can these things handle? Double EE's?



What are you using as a receiver for the transmitter unit? Have you tried tuning the capacitor through its entire range? Be sure to use a finger nail or other non-metallic object for tuning the transmitter frequency. These transmitters will take quite a bit of abuse, I dropped mine on the concrete floor a few times and it still works! If your transmitter doesn't work, inspect the board for "cold" (or improper) solder joints using a manifying glass. Did you form the hand wound inductor properly (coils evenly spaced), did you scrape the insulation off the ends before you soldered it to the board? Are you sure there are no solder bridges under the IC chip? Check that you have the right parts in the right places on the board. Were there part substitutions made either by you or JB Gizmo that aren't the same as those specified?

Bruce S. Levison, NAR #69055
Got the transmitter working and tunned. I learned how to use the desoldering braid as well.

I had planned on using a small AM/FM reciever on hand which has a 19" antennna, but it doesn't seem to pick up the signal util right on top of the transmitter. On ther other hand...I have a second reciver with a broken antenna that seems to work very well. Go figure.

Looking forward to experimenting with the transmitter. I will try a couple of "safe" shots before steping up to overpowered launches.

Have y'all tried your transmitters in the field yet?

Thanks for the advice.
Where would you mount the transmitter in a dual deploy rocket? It will be a FAST flight... the nose would be most secure but if it was on the shockcord then I could tell if the rocket seperated. Is it just size or is the larger transmitter better? Man thats cheap!!!
What is the range in the air, the range on the ground is nothing compared to rockethunter but it is a good start. When you guys plan on testing them in the air? How could it be mounted to the shockcord?

What is with the multiple posts? Please try to keep your posting consolidated. Also, the members above have given you some valuable information, which you should graciously accept. If you are going to contradict everything people tell you, then don't bother asking because they will stop talking and you will learn nothing.

Interesting. I got a unit going running at 433.925mhz. 2km range on the ground with trees in the way. Custom design. Didn't know JBgizmo offered kits!

Hope those units work well! Good luck!
Originally posted by teflonrocketry1
Has anyone else noticed the radio tracking transmitters and/or the model rocket locator kits available from JBGizmo?

What did you think? [Snip]
I found this Website in 2004 and book marked it for a future project. I have so many ideas and not enough time nor money. I need to win the lottery to support my rocketry habit!

Originally posted by Jerry Baumeister on his Website
The kit includes all parts, schematic diagram, plans, a printed circuit board and all necessary components.

NOTE: This transmitter is covered by Part 15 of the FCC rules. Your operation of this device must not interfere with FM radio or TV reception of other people. You should not operate the transmitter above 108Mhz to avoid the possibility that it might interfere with aircraft navigation systems.
Bruce or Stewart,
Do you notice any FM interference with these transmitters?
If I read the above quote correctly, the FM transmitter is legal as long as it does not interfere with commercial broadcasts?
What happens if there is a 107.9 radio station within range of the launch site?

Thank you in advance for your help.