Attic Dipole Antenna Ham Radio

thingiverse

I designed this to hold a 2m vertical dipole in my attic. I cut the dipole for the 2 meter band. The 70cm band is a third harmonic and therefore has a very low SWR on the 2m antenna. The antenna is easily tuned across the entire 2m band amateur allocation and ends up less then 2:1 SWR across the 70cm FM portion of the band. The antenna could be easily cut for other bands such as 220 MHz (1.25m) band. Cutting the elements for 6m would be a bit large, but I supposed it might be possible if you have sufficient vertical space in your attic (I don't). I've only installed it vertically, but it could be mounted horizontally as well. The antenna should only be used indoors. I don't think it's durable enough or possible to sufficiently weatherproof the antenna for outdoor use. BOM: the printed part 1/2 wavelength of solid 6ga copper ground wire (plus a little for trimming) coaxial cable coaxial connector for your cable To assemble the antenna: Cut two lengths of the 6 ga copper wire a little longer then 1/4 wavelengths (20" is a good starting point for 2m) Optional: put one end of the elements in a vise and chuck the other end in a drill. while spinning the drill, pull on the element. this straightens out the element and also work hardens the copper so that it's more stiff. Decide which way you want to mount the bracket, decide which was is up. (it doesn't matter, either way is fine) insert one of the cut elements into the top hole insert the other cut element into the bottom hole. Push the elements together so they touch in the center. put a small bend in the top element, immediately above the top hole. (this prevents the top element from falling out) The bend almost looks like a kink. Like a shallow "U" in the element. put a small bend in the bottom element, immediately above the bottom hole. (this prevents the bottom element from falling out. Solder the center conductor of the coax to the top element solder the coax shield to the bottom element. make certain the bottom element and top element are not touching! If they're touching, re-do one or both of the bends so they are not. dress the coax into the channel on the bracket use zip ties to affix the coax to the bracket using the provided holes Screw the bracket to anything you want in your attic. final trim ends for low SWR. I'll try to get some photos uploaded of the finished antenna with the coax soldered and dressed along the bracket. It's ugly, but you can have an antenna for only a few dollars. It works really well!