Antenna Launching Questions

Antenna Launching is a term we developed to describe putting Antennas up into the trees for Emergency Communications and Amateur Radio. The process starts by launching a weight towing a light line into the tree(s), followed by pulling heavier lines, and finally pulling the antenna aloft. Many different tools have been employed for this purpose, from fishing sinkers and slingshots to bows and arrows. We have tried just about every one. Tennis balls are the safest launch weights we have found, and pneumatic launchers are the most effective tool we have developed for Antenna Launching.

It is often more convenient to use existing trees than to erect supports for wire or beam antennas, especially when these antennas are required for temporary or emergency field use. We set up antennas for disasters and drills, camping and contests, practice and fun. With all the applications for Homeland Security there are many potential uses for rapid deployment. If you have a need to quickly set up antennas in various field situations, or you have some really nice trees in your backyard, you may have a use for Antenna Launching.

It is a very simple system that uses the energy in a pressurized volume of gas (generally air), a valve to release the gas, and a projectile (tennis ball) in a tube that is accelerated by the expanding gas giving it the required velocity to pull a light line over the tree.

We have used many different systems since the 70's to put lines up into trees. Each system has advantages and disadvantages. Throwing an object over a limb is the easiest, but will not reach very high, and there is a significant chance of getting the object stuck. Slingshots reach higher, and Bows reach higher yet. The main problem with most these systems is the projectile. A lead sinker, arrow or wrench can do a lot of damage if it lands in the wrong place, and regulating the amount of power in each launch is difficult. If you are putting a line over a tree in your yard, there are often local ordinances against using slingshots and bows. What is needed is a safe projectile, and a means for getting it over the tree precisely for maximum safety and effectiveness. If you have a really tall tree, then a Tennis Ball Launcher will allow you to go higher than most slingshots or bows. Even a small Pneumatic Tennis Ball launcher can reach up more than 100 feet, and it is possible to go much higher with the more effective models.

You might consider a Pneumatic Launcher if you are interested in more Performance or greater Safety. Slingshots and Bows work, but Pneumatics work better. Eric's big launcher can put a tennis ball up over 600 feet high (with no line). The small CSV19 reaches up to around 200 feet towing line, and the diminutive CSV17 goes over 130 feet towing line. These launchers are 19 and 17 inches long, respectively, and the heights are measured length of line pulled out. Add about 9 or 10 feet to those numbers to get the apogee, since the reel is about 10 feet off the ground when launching upwards. You can make launchers go higher, and we have, but the availability of trees that tall and feedlines that long makes it rarely useful. So I scaled these pneumatics back to the smaller sizes. Also be very careful with the slingshot and bow, there are many injuries each year, especially with slingshots.

If you are going to put up an antenna in the backyard the tennis ball is a lot safer than a lead sinker, and much easier to explain to your neighbor.

There are three primary reasons to use Tennis Balls. They decelerate quickly, are very visible and carry the line well. They are Safe and Effective. I have read of so many accidents with slingshots each year that I cannot recommend them. A lead sinker flying through the air is potentially an accident waiting to happen. You cannot see them in flight. They bounce off the tree, the line snags and the sinker returns on the line rebound, or they get hung up and come sizzling down when the line is pulled, potentially at higher velocity than even the slingshot can impart. The slingshot is not the problem, the projectile is the problem!

A Tennis ball is inherently a fairly safe projectile. They are big so they slow down quickly, limiting the distance they will travel and the velocity they impact with. They are not hard, so they tend to do little damage when they land. It is something familiar so people know what to expect. It is big enough to see fairly well. They are available and inexpensive.

Launcher performance is dependent on many things. Altitude, temperature and wind have effects beyond the characteristics of the launcher, line and balls. So numbers vary even for the same equipment.

Generally 130 to 200 feet of height is easily attained with a Pneumatic Tennis Ball Antenna Launcher while towing a 50 pound test fishing line. It is possible to go higher with the more efficient or larger launchers and heavier projectiles, but we have not found suitable antenna trees much over 130 feet tall. So we consider 130-150 feet to be about optimal. We generally don't carry sufficient feedline to put antennas much higher than about 100 feet anyway.

• Cutting high tree branches using a pull-chain saw
• Deploying Safety Lines for roof, tree or tower work
• Putting climbing lines in place for treetop canopies
• Training dogs for fetching after a mild report
• Putting a temporary wire antenna part way up a tower without climbing
• Putting a line across a pond
• Fishing - Casting far out in the surf or lake

If you've played or watched tennis you know that the serve is (usually) one of the faster strokes in tennis. Well, a good serve has more velocity than is required for launching a tennis ball over most tall trees. The ball slows down quickly, and on the far side of the tree (towing the fishing line) it comes down very slowly. Our launchers use velocities lower than a fast serve.

The simplest material for building an Antenna Launcher is Schedule 40 pressure rated PVC. This material is designed for working pressures in excess of 200 pounds per square inch, and the pressures we use are up to 60 or 90 psi. So while the pressures are within design parameters, the manufacturers of PVC pipe and fittings RECOMMEND AGAINST its use with COMPRESSED AIR. If PVC containing compressed air is fractured, it may result in high velocity PVC shrapnel. So avoid breaking it while it is pressurized, and wear safety glasses when using launchers just like any power tool. Low and high temperatures make PVC brittle or soft so launchers should not be used in extreme temperatures. Note that in many years of making and using these launchers we have seen a few broken in various ways and never have we seen any small pieces break off that could become shrapnel. The low volume and pressure we use is not likely to produce this problem.

Here in the US the Federal BATF (Bureau of Alcohol, Tobacco and Firearms) has ruled that pneumatic launchers are NOT firearms. Some Municipalities have regulations that may affect the use or ownership of Launchers. Such rules are not common, and the ones that do exist usually focus on combustion type launchers rather than pneumatics. Check with the local authorities to be sure. Note that slingshots and bows are generally illegal to use in residential areas, parks, campgrounds, etc. Here is the letter from the US BATF on the subject.

The materials for a launcher cost between anywhere from about $60 to $100 or more, plus a reel, some line and a few tennis balls. If you have leftover parts from a lawn sprinkler project it may be much less... Launcher Kits with all the parts machined are available starting at about $100, see the Product List.

It depends on the model, and it ranges from fairly simple to quite complex. If you can cut and glue PVC and thread pipe fittings together you can build the simple models. Some require drilling and tapping a hole or two in the plastic, some need a little soldering. Kits are available for some models, so the hard parts are already done. The time required varies from a few hours on up. The more complex designs may require a friend with a lathe to machine some PVC. Generally speaking, as size/weight/cost go up, so does performance. A low performance design might require 80 psi to launch 150 feet high, whereas a higher performance design might do the same job at 25 psi. Choose a design that matches your construction ability, budget, size requirements and the trees you need to launch over.

It depends on your trees.

Since this is the business site we will recommend the CSV17 or CSV19 launcher kits available on the Products pages. The main difference between these two designs is size - the CSV17 is 17" long with a 3" diameter chamber. The CSV19 is 19 inches long with a 4" diameter chamber. The CSV17 is much easier to take to the field since it fits into an 18 inch tool case. The CSV19 fits into a Rubbermaid(tm) 10 gallon tote.

If you want convenience for storage and carry the smaller CSV17 is excellent. If your trees are over about 120 feet tall you might want to opt for the larger CSV19.

For more choices and designs for homebrew you might want to visit the AntennaLaunching pages.

This is the name for the Launcher-in-a-case shown on the PADS Web Page. The CSV17 launcher fits nicely into this hard case. It may be small but has been able to reach over 130 feet in height. The PADS launcher and hard case are available on the order page. Also shown are a pair of Twine Reels containing 500 feet of nylon twine. They are available in 270 foot lengths as well. The grey cylinder near the bottom center of the photo is a bicycle type CO₂ tire inflator. It can be used with a number of different capacity CO₂ cylinders. Using the low-cost 12 gram cylinders produces enough pressure for one good launch per cylinder. Also in this case, but not visible is a 12 oz Paintball CO₂ cylinder stored inside the barrel, along with two tennis balls. The CO₂ pressure regulator is behind the right end of the ramrod. There are a total of six tennis balls in this photo, two hidden in the barrel and one hidden inside the reel on the lower left. The Mini-Coaxial reel on the lower left is a special reel made for this launcher to fit in the case. It is a scaled-down Zip-type reel with about a one foot circumference. Just behind the launcher's trigger is a bag of 12 gram CO₂ cylinders for the bicycle inflator. Visit the PADS Web Page.

The simplest pneumatic launcher is a pressure storage chamber, a barrel, and a ball valve in between. These are not particularly suitable for antenna launching because the performance is dependent on how quickly the valve is opened. Additionally, opening the valve manually disturbs the aim, so it will be difficult to make it go where desired.

Combustion type launchers use lighter fluid, spray deoderant, propane or some other fuel in a closed pipe chamber behind a projectile with an ignition source to light it off. These are frequently referred to as "Potato Guns" since they often use cores of potato or other vegetables or fruit as cheap bio-degradable fun projectiles. In addition to some safety concerns, combusion launchers may produce somewhat inconsistent shot-to-shot performance due to their imprecise fuel-air mix, which makes them difficult to use as a serious Antenna Launching tool. They also misfire occasionally, require cleaning and maintenance and are more often legally restricted than pneumatic systems. Let's not use them for Antenna work!

First, I'll define 'effective' as any launcher that can toss a 4 ounce tennis ball to a height of at least 120 feet towing a fishing line. That is pretty adequate for our purposes.
The smallest launcher that meets this criterion that we have built is the CSV17 shown above in the PADS kit. This is a 17 inch long model. The popular CSV19 Compact Low Cost Sprinkler Valve Antenna Launcher and the Quick Exhaust Valve Launcher are only a little larger. At about six pounds, these are small enough to fit into a Rubbermaid tote box, or less than 19 inches in length. There is plenty of room left in the tote box for line, antennas, feedline, and other equipment.

The CSV19 Compact Low Cost Sprinkler Valve Antenna Launcher is assembled from plumbing parts most of which are available from local plumbing or home improvement stores for under $100. Some machining is required to make them fit together as shown above. The dark grey barrel is SDR21. Schedule 40 also works, but the ball is very tight. SDR21 fits better but is harder to find. This is the lowest cost simple to construct launcher I have designed (the CSV17 variant is a little easier and even less costly). The link above has fairly complete construction instructions. The collection shown above is shown complete with Saunders Zip Reel with yellow Spectra type synthetic line, and a couple of prepared Tennis Balls sitting on a Rubbermaid 10 gallon tote. The gear fits into the tote with room to spare.

The pressures and volumes involved are similar to a bicycle tire, so automotive or bicycle air pumps are just about right. The portable 12 volt electric ones are handy. They run from a car battery or are even more portable with a built in battery. Hand or foot pumps work well also, and have the benefit of a good aerobic workout. Some folks use CO₂ systems which are very convenient. I recently have been testing two CO₂ systems - a Paintball cylinder and regulator, and a Bicycle tire filler using 12 gram cylinders. CO₂ systems cost a bit more to own and operate, but they are pretty amazingly effective and fast.

I tested a 6 gallon compressed air tank recently and starting with 100 to 110 psi was able to get about 15 shots at 50 psi from it with the CSV19 launcher. The smaller chambers on the CSV17 and QE19 would get even more launches per fill.

We have a portable battery powered filling station from Harbor Freight. This has become a favorite for charging the launcher. It takes about one minute. Ours has a 12 volt 17 amp-hour battery and a compressor and was under 50 bucks. After you launch the antenna you can hook up to the 12 volt gel battery and run the station!