Scratch Cheap Tracking Transmitter Original Design / Scratch Built

Scratch - Cheap Tracking Transmitter {Scratch}

Contributed by Terry Bendell

Manufacturer: Scratch
Cheap Tracking Transmitter
(Contributed - by Terry Bendell)

I thought I would share with you a neat way of locating your rocket if it blows off course. I was in Radio Shack a few months back and I noticed they had a sale on the FM wireless Microphone (Part# 280-4030) this little transmitter can be tuned between 90-98 Mhz, thus letting you use a standard portable FM Radio/Walkman to hear it. It is regularly on for $16.99 (Canadian pesos) but I picked up two of them for $9.99

This little Transmitter runs on a simple 1.5 volt Hearing aid battery, You can use the larger 1.5 volt type "N" battery it suggests if the extra weight isn't a factor. I found it works just great for 15 hours or more just on the tiny battery.

Building it (it's a kit!) is a snap. The only thing you should do is omit mounting the little condenser microphone, you don't need it unless you like to hear the wind scream through your rocket and the ejection charge going off. Otherwise its just extra weight.

I built mine in about an hour and launched it on my Comanchee 3, The first launch was perfect, the little radio worked perfectly. I was able to locate my rocket as I saw it land. The Next launch at apogee I shut my eyes and did not see the rocket return. Using my portable FM Walkman I was able to locate my rocket by walking around and turning my body while not moving the Radio, I located my Comanchee 25 minutes later in a large field about 3 city blocks away. The little transmitter works great! Only problem that I can see is that you may have a hard time finding a fairly clear frequency between 90 to 98 mhz without big commercial stations walking over the signal. Fortunately up here its pretty uncluttered.

Hope this helps someone else who is looking at a cheap and fun/reliable way of rocket location. I can even see a whole new sport rocketry event "Rocket Location and Duration".

Thanks and good hunting.

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