A Stored Energy Antenna Line Launcher
By Richard Morrow, K5CNF

o doubt, there are times when you have needed to string up an antenna wire using a tree. In this article, an homebrew method is described about building a “launcher” for installing antenna support lines over high limbs and other tall objects. This is a typical problem that many have dealt with on Field Days and various other operations in the field. In the past to get a line over a high branch or other thing that could support an antenna, I have used everything from throwing rocks with the line taped to them, launchers made of fish casting rods, bow and arrows and a crossbow.

SLING THIS SHOT
The bow and arrow and the crossbow are methods that must be used with extreme caution because both of these projectiles have points that can injure someone or do damage if they hit anything coming down. The crossbow was produced mixed results. The little arrow went high enough, but it did not stop there. It took all the line and vanished into the sky dropping 600 yards away from where it was launched. It appears that a 100-lb draw on the crossbow was a little too much power. The regular bow did much better because the amount of power can easily be adjusted by the amount of draw on the bow. However, it was rather large and awkward to carry into the bush. Throwing the wire on a rock was not very good either—the right size rock may be hard to find and it takes a really strong arm to get the rock and wire very high. So, some easier method was needed to suit my needs.

Many years ago I had seen a slingshot device described in one of the ham magazines that would do just what I wanted. I don’t remember the ham that came up with the idea, but it ended up on the market and a commercial version is still advertised in the ham magazines. The device consisted of a typical rubber powered “sling shot” or catapult called a “Wrist Rocket” and a closed-face fishing reel mounted on a rod in front of and under the “Wrist Rocket”. This system used small weights that were shot over a branch or other high support. I thought that this was a rather nifty way to do this function, but did not feel like spending the amount of money wanted for the commercial device.

A CHEAPER WAY
I decided to build a homebrew version of this device and went shopping for the parts. I found a Zebco closed-faced reel on sale for $5 USD at a local discount store. I also found a slingshot at another store at a reasonable price of less than $5.00.  I now had the major manufactured components for under $10.00 USD. Then, a bit of rummaging through my scrap pile of PVC yielded a short length that the handle of the slingshot would fit into easily. Another 1/2-inch piece of PVC was located as a mount for the Zebco reel. Photos 1 and 2 show how the Zebco was mounted on the small length of the PVC. I used a tie wrap rather than glue so that I would be able to replace the reel should it ever fail.

Photo 1

Photo 2

Next, I cut out a portion of the PVC as shown in Photo 3. This allowed me to hold the PVC and the handle with my hand. It also allows the device to be disassembled for transport. The tape shown is only to hold the slingshot in place for the photos to be made. The slingshot will sit down snuggly within the small PVC pipe handle when it is being used.

Photo 3

Photo 4 shows the two major components of the system. Photo 5 is of the device when assembled. The 1/2-in PVC is inserted in the holes previously drilled in the larger handle section of the PVC. The components may all be glued in place if desired, but for my purposes, I wanted to be able to take the system apart for travel.

Photo 4

Photo 5

To use the system after assembly, a lead pear-shaped fishing weight in the range of 3/8 to 1/2 ounce or larger is tied onto the line of the reel. Then the line lock on the back of the reel is pushed in to release the line. The lead weight and the line is passed through the yoke of the slingshot and into the pouch at the end of the two rubber tubing lengths. Now the assembly is ready to use as a launch!

PRACTICE MAKES PERFECT
Take care when aiming the line with its lead weights and look beyond your targeted limb or support. Be sure to carry several spare weights along and some practice using the launcher would be a good idea before using it in the field.  -30-

Current rigs are TS-430S, TS-700 multi-mode, Kenwood two FM meter rig, Icom 440 ht. Radio Shack HTX-100, Radio Shack 440 ht, 2 Atlas 210x, Johnson 275 watt Matchbox, Johnson Thunderbolt, several older SGC SSB marine rigs, three Heathkits.

Interests include; antennas, astronomy, music, both radio and optical, reading, photography, motorcycles, archeology, cars, Cosmology, Science in general, Nature, animals and aviation.

~ antenneX ~ May 2002 Online Issue #61 ~

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