Brief:
I've been searching for a radio tracking system for my rockets for several
years. When I first got back into rocketry several years ago, I set a goal for
myself to send a rocket a mile high and get it back. Well, going a mile high
isn't difficult, and proving it is fairly easy by using one of the array of
rocketry altimeters available now. Getting the rocket back is the difficult
part--I can't even count the number of rockets I've lost. I tried tracking
powder, metallic mylar streamers, recovery screamers, smoke bombs, and all
kinds of other things to make tracking and recovering my rockets easier. Some
worked better than others, but none were perfect.
Then I looked into radio tracking transmitters, however, there are a few problems with most transmitters available for hobby rocketry. First, if you don't have an amateur radio technician license, you are limited in the (frequency and power) range that the transmitter is good for. I purchased one of these limited range transmitter/receiver combos. It worked great on short range recoveries in dense brush or high grass, but it wasn't good much beyond about 300 feet. Second, there are some other non-licensed systems with tremendous range (up to 10 miles), but they were out of my budget (in the $500-$600 range). Finally, some companies have recently introduced much less expensive tracking systems for rocketry, but you need a license to purchase them. (Yes, I know you don't need to learn Morse code any more for the license, but I'm "electronics challenged" and memorizing the answers to more than 300 questions dealing with electronics just isn't for me.)
Enter Communications Specialists, Inc. They have several kinds of tracking systems for tracking pets, a system for Radio Control model airplanes, and one for law enforcement. After checking over their website and seeing that their systems seemed to do what I wanted, I gave them a call. Originally, I was going to order their "PR-50" (a 50 channel receiver for $200) and their PT-1B (a short range transmitter for $50), but after talking with the helpful representative on the phone, I decided that range on the PT-1B was too short ("several blocks") and ordered the PT-2B (with a range of "several miles") for $99 instead. The system also comes with a "FA-1" (high gain directional antenna).
Construction:
The PR-50 is a 50-channel receiver with a three step attenuator (close, medium,
and long range) and is powered by a 9V battery. You can monitor signal strength
two ways: with the speaker and by the meter. It also has battery test switch, a
volume control, and a channel selector. The size is 6.3" x 3.5" x
2.7" without antenna. The weight is 21 oz with the antenna. The
directional antenna is 20" x 7.7" and attaches to the BNC connector
on the top. The unit has a good, solid feel to it and is easy to use
one-handed.
The transmitter is 1 3/4" x 7/8" x 7/8" including battery and magnet, less antenna. Antenna is an 8" long, loaded, black PVC coated, stainless steel cable, so overall size is about 10" long. Weight including antenna, battery, and magnet is less than 1.5oz. Power output is 95 milliwatts. It is powered by a lithium coin battery with a battery life of about 9 days. It has no "on/off switch". Once you insert the battery, the unit starts transmitting. My transmitter was programmed for channel 14, but you can order the unit to be on any one of the 50 available channels. Channel 14 corresponds to 218.125MHz, for those "electronics guys" out there.
Once I received the system, I tested it in the neighborhood. I placed the transmitter on the ground in my backyard and walked about 10 streets (maybe a thousand feet) away. I was able to receive a good signal despite the houses in the way. The receiver gives a simple "beep....beep....beep..." which gets louder the closer you point the antenna in the direction of the transmitter. The signal meter also shows the corresponding increased strength.
Flight and Recovery:
I had to wait almost 6 months before I could actually do a test flight with the
system. I took it out to the "Summer Skies" launch at Brothers,
Oregon on 6/16/2006. I first wanted to test it in my "Mint Stick"
rocket, a 4" diameter 67" long 7lb rocket. The rocket was not
designed to include a radio tracker, but there was enough room in the
electronics bay alongside the MissileWorks RRC2 altimeter. Although the
transmitter's battery snaps into place and I don't think would ordinarily pop
out, I placed a wrap of masking tape around the unit to make sure. I wanted the
transmitter to be somewhat protected, so I inserted it into a plastic
prescription pill bottle with a hole drilled in the bottle cap to allow the
antenna to stick out. This pill bottle was then zip-tied to the plywood
electronics tray and then duct tape was used as insurance.
The rocket was loaded with a J350 and placed on the pad. I was getting a good signal from the transmitter, and when the rocket was launched, I had no trouble maintaining the signal. At apogee (about 2500 feet), the ejection charge fired and the rocket separated into two sections, but the parachute did not deploy. The rocket came down in a flat spin and although the rocket itself is somewhat overbuilt and relatively "bulletproof", I thought the transmitter would be destroyed. However, I continued to receive a good strong signal and was able to find the rocket without a problem. The plastic pill bottle had shattered with only the duct tape holding it in place but the transmitter was undamaged!
The next day of the launch, I placed the transmitter in my new "Hobgoblin" clone. This is an 8" diameter 62" long 19lb copy of the old NCR "Hobgoblin". Once again, this rocket wasn't designed for the tracker so I had to fiddle with the installation. This time I used a 35mm film canister with a hole drilled in the lid as the holder, wrapping it with masking tape, and securing it to the altimeter tray. The rocket was loaded with a K1100 and the launch was perfect. At apogee, the ejection charge fired and the chute deployed correctly. I was able to follow the flight and landing (about a ¼ mile away) without a problem.
On the final day of the launch, I wanted to try the system in a high altitude rocket so I installed it in my "Mr. Pointy" rocket, a 3" diameter 45" long 3lb rocket. I had never tried this rocket with a J350 so that is what I loaded it with. The transmitter in its film canister barely fit in the altimeter bay but only after slightly bending the antenna. This launch was a little different. At about 100' up, the rocket came apart. Later examination revealed that one of the couplers couldn't handle the thrust, which caused a spectacular "semi-shred". The parts came down about 100' from the pad and I quickly gathered them all up. After dumping them on my prep table, I went to help someone else with their prep and didn't examine them for about an hour. That's when I realized that the transmitter wasn't with the rest of the parts. Somehow it had been thrown out when the shred occurred. I turned on the receiver and got a good signal that I followed right to the transmitter. The hardest part was actually finding the film canister on the ground! (Have you ever looked for a gray canister wrapped in brown tape on a ground of grays, tans, and browns? Next time I'll wrap the film canister in blue or red tape!)
Summary:
So, what do we know from all this?
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A.K.S. (September 25, 2006)