Amateur radio is an eclectic hobby, to say the least. RF propagation, electrical engineering, antenna theory – those are the basics for the Ham skillset. But pneumatics? Even that could come in handy for hanging up antennas, which is what this compressed-air cannon is designed to do.
[KA8VIT]’s build will be familiar to any air cannon aficionado. Built from 2″ Schedule 40 PVC, the reservoir is connected to the short barrel by a quarter-turn ball valve. Charging is accomplished through a Schrader valve with a cheap little tire inflator, and the projectile is a tennis ball weighted with a handful of pennies stuffed through a slit. Lofting an antenna with this rig is as simple as attaching a fishing line to the ball and using that to pull successively larger lines until you can pull the antenna itself. [KA8VIT] could only muster about 55 PSI and a 70′ throw for the first attempt shown below, but a later attempt with a bigger compressor got him over 100 feet. We’d guess that a bigger ball valve might get even more bang for the buck by dumping as much air as quickly as possible into the chamber.
Looking to launch a tennis ball for non-Ham reasons? We’ve got you covered whether you want to power it with butane or carbon dioxide.
Continue reading “Pneumatic Launcher Gets Ham Antennas Hanging High”
As an amateur radio enthusiast, [Andrew] sometimes has to set up impromptu antennas up to 160 meters in length. The easiest way to get these antennas off the ground is to drape them over trees, a feat normally accomplished by lofting fishing line into the air with a slingshot or bow and arrow. [Andrew] thought slings were so last century, so he came up with a spud gun inspired antenna launcher.
The launcher is built out of PVC and launches a foam filled tennis ball that can reel out 150 yards of Spectra line. In a moment of brilliance, [Andrew] decided to add an augmented reality HUD. The display is actually [Andrew]’s phone running an app called Geocam that provides him with a display of elevation and azimuth overlaid on the phone’s camera feed. The results of [Andrew]’s build are fairly impressive. The cannon was able to lob a tennis ball over a 110 foot tree at half the pressure rating of the PVC. The grouping was pretty tight as well, more than sufficient to run a line over a tree.
[Andrew]’s antenna cannon is an awesome piece of work and unlike most french fry cutters, it’s a useful tool. If you’re interested in seeing 160 meter antennas heaved over the tops of trees, amateur radio field day is next
month week, June 25th and 26th.