PRACTICE BEACON BOX
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There are two basic sizes of ammo can that you will want to use, the 5.56mm or 50 Caliber can (medium size), and the 7.62mm can (narrow size). There are larger cans, but they would be too bulky. The can you want should obviously be able to contain your practice beacon. As an example, the can used for this page says "840 CRTG 5.56MM BALL M193 10 ROUND CLIPS." Translated, the box originally held 840 rounds of plain M-16 .223 caliber ammunition held together in 10-round zinc stripper clips. I wish I hadn't spent the 'worser' part of a summer at college loading those type of strippers into magazines. The 7.62 can fits the width of the Pointer Practice Beacon perfectly, eliminating some of the slop and banging around the beacon could take, but will not allow as much padding on the sides. If I were going to make another beacon box, I would use the 7.62mm variety as it is overall a better choice.
The procedure suggested here is certainly not the only way this project can be accomplished. It only describes some of the pitfalls and suggests one possible method. A Radio Shack BNC connector is listed in the parts list above. This will work, but only with moderate results. After testing and use, a better solution is to have a panel mount BNC connector that has a female BNC connectors on BOTH ends. The problem is that the coaxial cable is very difficult to stabilize to the container, even with large amounts of solder and hot glue. Furthermore, a double-ended BNC connector allows a short length of coax to connect to the inside of the can, or to another antenna as described below. A part number is not available for this double-ended female BNC panel mount connector. first, drill a hole in the top of the ammo can. Your drill bit size should follow the specification on the package of the panel-mount BNC connector. I recommend drilling the hole on the hinged side of the can to allow the use of the shortest possible coaxial cable. If you place the hole on the latch-end, your coax cable must be able to extend enough to allow for a full swing of the can lid. Now that your hole has been drilled, you will need to rid yourself of the paint from around the underside of the hole. You'll want to strip about 1/8th of an inch from around the hold down to bare metal. It may not be a bad idea to do the same on the top of the hole. Stripping the paint will allow a good electrical connection between your box and your the BNC connector you are installing. A good electrical connection is necessary to allow the practice beacon to properly radiate. Paint is an electrical insulator. To clean off the paint, use a combination of scratching and sanding. A dremel rotary tool would be very useful to do this. The metal beneath should be clean and shiny. After the hole has been cleaned, you might note that there is a gap between two pieces of sheet metal in the lid. Crunch the bottom metal into the top using a vise, a large C-clamp, or even a bolt, some washers, and a nut. The bottom line is that you will have a better product if the metal is closer together.
Place the Practice Beacon inside the can, resting on the bottom.
At left, note
how this user constructed the beacon box in such a way that requires the
coax cable to meet the beacon at a right angle.
A You must always use some sort of antenna on your Practice
Beacon. If you don't, you'll overmodulate the unit and prolonged
operation will essentially
burn out the transmitter. While the rest of the ammo can is going to
be virtually indestructible, the antenna on the top will b If your Practice Beacon has a radio station license and/or a log, you will have plenty of additional space to put it inside of your ammunition can. Some users choose to use a form of external battery. If you would like to do this, there will be plenty of room for this inside of your ammo can. If you'd like more information on how to modify your beacon to accept external power, see the Practice Beacon Modifications page on this site. OPTIONAL: While many searchers look for the Pointer's familiar orange or black box with a red light, you may want to change that appearance. I recommend painting the box with international orange paint. It is also wise to stencil the owner's information and a contact phone number on the exterior of the can. Orange will make the unit harder to hide, but I would counter with the fact that if you are close enough to see an orange box in the woods, then you are close enough to find a wrecked airplane. Furthermore, an orange ammo can resembles a cockpit voice recorder (CVR) or flight data recorder (FDR) that are carried abort transport category aircraft. Some people still call these "black boxes," when in fact they're most often international orange! OPTIONAL: If you live in a part of the country that gets cold, remember that your practice beacon's batteries won't work as well when they are chilled. Just as with real ELT batteries, however, they should work longer in this condition, but at a reduced power output. To help prevent this from happening, place a sealed chemical hand warmer inside the box near the battery pack. The foam rubber you already included is great insulation, but think about where the cold can conduct away your heat inside the metal box and insulate that, too. Many department and sporting goods stores now sell reusable hand warmers that you can use and recharge by boiling in water. If you are having trouble finding something like that, try in places that sell hunting supplies. There is a common misconception that cold temperatures decreases the life of ELT batteries. In actuality, cold weather will prolong the life of an ELT but at a reduced power. When very cold, the power output can be effectively nothing in a very short period of time! The batteries will come back to life once they warm up. The prolonged life is the reason why some people will store their ready-to-be-used batteries in the refrigerator. This is not a recommended practice because battery cells will give off gas that lightly can poison food. This is especially true of mercury batteries, but these are difficult to find on the commercial market. OPTIONAL: The weakest point on the box is now the BNC connector on top. When I was doing some work with copper pipe in the house, I cut off about a 3/4 inch of the 1 inch diameter copper pipe I was using. This would have otherwise been scrap, but I put it to good use. I hot glued that piece so it would fit all around the BNC connector. If there is no antenna on the box, the pipe piece will take the abuse that the BNC connector could not. Pipe is cheap, connectors are not, and they're much more difficult to attach! I simply hot glued the piece onto the box. I could have used pipe solder, but I had no more available. A special thanks to Heath Calhoun, Mike McDonald, and Bob Stimble for this thread on the CAP-ES talk listserver. They confirmed this design was workable and suggested a few details which I had not considered.
I have recently learned that some "evil" hiders are submerging practice beacons to add to the difficulty of the hunt. This may generally seem to be excessive, but an ELT can radiate after a ditching. More importantly, it can be found! The ammo can is one method of accomplishing this, provided that it is sufficiently weighed down. See the Underwater ELTs page for more information. An important note: a definite effort was made to call the Pointer 6000 a "Practice Beacon" versus a "Practice ELT" or an "ELT." Although sometimes difficult, it is a good idea to refer to training ELTs in this manner. If you call your training aid a "Practice Beacon" on the radio, people who monitor are much less likely to get excited. In the past, there have been responders to 'ELT missions' when the target was actually a practice beacon. I'm sure I slipped somewhere in this site, though. The term "PELT" for "Practice ELT" may also be misleading. This acronym was used some time ago for "personal" ELTs, also called PLBs (personal locator beacons) or PETs (Personal Emergency Transmitters). |
This page of the CAP Emergency Services Resources™ website was last updated 02/04/2007
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