I had the urge to build *something*, and an 8-foot 20m short loaded vertical made out of PVC was the result. It uses a lumped inductance, and not continuous helical wind like a hamstick.
It may not be optimal (yet), but the objective was to just put some household materials to better use than just sitting on the shelf. Inspired by my portable Hustler mobile antenna setup, and using the same radial grounds, I thought I'd give it a try and see if using PVC for both the coil form and the antenna mast itself would work. Speed, repeatability, some limitations, and a reasonable response for at least rx-only was the primary goal. Optimization can come later.
MATERIALS:
8 Feet of 1-inch labeled id PVC. (appears to be about 1.5 inches OD) I put a self-imposed limitation as 8 feet. Two pre-cut pieces (both at 5 feet) from the hardware store were laying around, so I used a coupler. I cut two feet off of one piece so that when coupled, it wouldn't exceed 8 feet and would not go beyond my backyard overhang and I could store it vertically in a closet. This serves as both the coil form, and the mast itself.
#12 covered copper house wiring. I had a roll of it laying around so I used it. The antenna contains no breaks, and is just one continuous length including the coil.
Electrical tape, wire cutters, and an antenna analyzer.
BUILD:
Starting at the bottom, I taped 5 feet of wire up the side of the pvc until I hit the coupler. At that point just beyond the coupler, I wound 38 turns close-spaced for the coil going upwards. This coil ended up being about 4 1/2 inches long, and the rest was run straight up the rest of the way until I reached 8 feet overall. In the end, the wire above the top of the coil ended up being 27 inches long after trimming. There is no "stinger" per se - what comes after the coil is just taped to the pvc for mechanical rigidity.
At the bottom, a 3-inch little jumper goes from the pvc antenna to an LDG 1:1 balun/rf choke, and the radial ground from my Hustler was used.
RESULTS and NOTES:
The results are good, although I am just using it for rx-only. I can't switch back and forth fast enough between my Hustler and this homebrew to give any specific gain differences - although the analyzer showed that indeed, my homebrew is NOT as efficient.
But it isn't a dummy-load either!
Initially I had used 40 turns for the coil, and while I could trim the length for resonance, it was TOO broadband. So I unwound 2 turns from the coil (which conveniently gives back some more wire length to trim later), and this narrowed the Q to something more reasonable - it covers the whole band well, but I may go back later, remove another turn or two, and really narrow things up.
OPTIMIZING:
I didn't set out to build the most efficient short loaded vertical. I just wondered how bad 5 minutes of time, tape, pvc, and cutters would do. I wouldn't pump rf into it unless you optimized it a bit more to get the efficiency up.
If I had the materials around, I would have used bare wire, spaced the coil turns 1 wire diameter apart, created a capacity hat of at least two opposing 1 foot wires for example, used 3 inch pvc, etc etc.
I had a lot of fun building this thing, and watching the Q go up as I removed turns from the coil and re-resonated was fascinating. Next time, maybe I'll try an 8-footer made out of 3 to 4 inch pvc for 40 meters. Sure beats sitting on the shelf doing nothing...
It may not be optimal (yet), but the objective was to just put some household materials to better use than just sitting on the shelf. Inspired by my portable Hustler mobile antenna setup, and using the same radial grounds, I thought I'd give it a try and see if using PVC for both the coil form and the antenna mast itself would work. Speed, repeatability, some limitations, and a reasonable response for at least rx-only was the primary goal. Optimization can come later.
MATERIALS:
8 Feet of 1-inch labeled id PVC. (appears to be about 1.5 inches OD) I put a self-imposed limitation as 8 feet. Two pre-cut pieces (both at 5 feet) from the hardware store were laying around, so I used a coupler. I cut two feet off of one piece so that when coupled, it wouldn't exceed 8 feet and would not go beyond my backyard overhang and I could store it vertically in a closet. This serves as both the coil form, and the mast itself.
#12 covered copper house wiring. I had a roll of it laying around so I used it. The antenna contains no breaks, and is just one continuous length including the coil.
Electrical tape, wire cutters, and an antenna analyzer.
BUILD:
Starting at the bottom, I taped 5 feet of wire up the side of the pvc until I hit the coupler. At that point just beyond the coupler, I wound 38 turns close-spaced for the coil going upwards. This coil ended up being about 4 1/2 inches long, and the rest was run straight up the rest of the way until I reached 8 feet overall. In the end, the wire above the top of the coil ended up being 27 inches long after trimming. There is no "stinger" per se - what comes after the coil is just taped to the pvc for mechanical rigidity.
At the bottom, a 3-inch little jumper goes from the pvc antenna to an LDG 1:1 balun/rf choke, and the radial ground from my Hustler was used.
RESULTS and NOTES:
The results are good, although I am just using it for rx-only. I can't switch back and forth fast enough between my Hustler and this homebrew to give any specific gain differences - although the analyzer showed that indeed, my homebrew is NOT as efficient.
But it isn't a dummy-load either!Initially I had used 40 turns for the coil, and while I could trim the length for resonance, it was TOO broadband. So I unwound 2 turns from the coil (which conveniently gives back some more wire length to trim later), and this narrowed the Q to something more reasonable - it covers the whole band well, but I may go back later, remove another turn or two, and really narrow things up.
OPTIMIZING:
I didn't set out to build the most efficient short loaded vertical. I just wondered how bad 5 minutes of time, tape, pvc, and cutters would do.
I wouldn't pump rf into it unless you optimized it a bit more to get the efficiency up.If I had the materials around, I would have used bare wire, spaced the coil turns 1 wire diameter apart, created a capacity hat of at least two opposing 1 foot wires for example, used 3 inch pvc, etc etc.
I had a lot of fun building this thing, and watching the Q go up as I removed turns from the coil and re-resonated was fascinating. Next time, maybe I'll try an 8-footer made out of 3 to 4 inch pvc for 40 meters. Sure beats sitting on the shelf doing nothing...
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