A Parasitic Lindenblad Antenna for 70cm - N3UJJ
A Parasitic Lindenblad Antenna for 70cm - N3UJJ A Parasitic Lindenblad Antenna for 70cm - N3UJJ
A Parasitic Lindenblad Antenna for 70cmPVC riser using an insert-to-threaded adapter. These PVC components are of the typeused for lawn irrigation systems. The coaxial feed line is attached directly to the drivendipole using aluminum sheet metal screws.PartsThe hardware components used in this antenna were readily found in a local ACEHardware store and most of the parts are not critical so feel free to substitute as needed.However, the aluminum tubing used for the driven dipole must be ¾” outer diameter andconstruction will be easier if the tubing is 17-gauge as the inner wall will be just slightlysmaller than the outer wall of a PVC-insert-connector. If heaver wall tubing is used, it will benecessary to file down the PVC insert-connector to make them fit together.Table 1. Parts listQuantityDescription2 6-1/16” length of ¾” OD, 17-gauge, aluminum tubingNote: Available from Texas Towers www.texastowers.com4 11.75” lengths of #8-AWG aluminum ground wire (or 1/8” OD tubing)1 ½” x ½” gray PVC insert connector1 ½” to ½” gray PVC insert-to-threaded adapter1 12” x ½” threaded gray PVC riser4 5” x ½” gray PVC ferrule for spacing rain gutter nails1 1” to ¾” PVC electrical conduit adapter2 #6 x 3/8” aluminum sheet metal screw2 #8 x ½” aluminum sheet metal screws2 Fair-Rite cable ferrite. Part# 2643540002.Note: Available from Mouser Electronics, www.mouser.comStock# 623-26435400021 3-foot to 10-foot length of Times Microwave LMR-240 coaxial cable1 Male N-connector for LMR-240 coaxial cable1 ¾” Black plastic end cap4 ½” Black plastic end capMisc.Heat shrink tubing for 3/4” cable, Regular bodied gray PVC solvent cementfor Carlon conduit,, Marine Goop outdoor waterproof contact adhesive,Ox-Gard OX-100 grease for aluminum electrical connections, black wireties8AMSAT PROCEEDINGS 2006
A Parasitic Lindenblad Antenna for 70cmThe LMR-240 coaxial cable was selected because of its low-loss, low cost and wideavailability but any 50-ohm small diameter cable may be used. The cable ferrites have a0.25” inner diameter so the cable needs to be smaller than this to fit.AssemblyStart by making the parasitic element assemblies, see Figure 4. Cut the plastic ferrules to3-3/4” length. Drill a 1/8” hole through each ferrule 3/16” from the end. The hole should gothrough both ferrule walls and be centered as much as possible. Push a ground wirethrough the hole in the ferrule and center the wire so that it sticks out the same amount onboth sides of the ferrule. Apply the Marine Goop liberally through the end of the ferrule tocoat the wire and the inside of the ferrule wall. Set these aside for several hours until theGoop is dry.3 -3/4”3/16”1/8” hole”#8 AWG aluminum wireFigure 4. Parasitic element assemblyNext make the driven dipole assembly. Please see Figure 5. Gently tap the PVC insertconnector into the two pieces of aluminum tubing with a mallet or hammer until they arespaced ¼” in the center. The overall dipole length should be 12-3/8”. Then, drill a hole for a#6 screw, 3/8” from end of the tubing at the center insulator. Directly across the insulator,also spaced 3/8” from the end, drill a hole for a #8 screw.AMSAT PROCEEDINGS 20069
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A <strong>Parasitic</strong> <strong>Lindenblad</strong> <strong>Antenna</strong> <strong>for</strong> <strong>70cm</strong>The LMR-240 coaxial cable was selected because of its low-loss, low cost and wideavailability but any 50-ohm small diameter cable may be used. The cable ferrites have a0.25” inner diameter so the cable needs to be smaller than this to fit.AssemblyStart by making the parasitic element assemblies, see Figure 4. Cut the plastic ferrules to3-3/4” length. Drill a 1/8” hole through each ferrule 3/16” from the end. The hole should gothrough both ferrule walls and be centered as much as possible. Push a ground wirethrough the hole in the ferrule and center the wire so that it sticks out the same amount onboth sides of the ferrule. Apply the Marine Goop liberally through the end of the ferrule tocoat the wire and the inside of the ferrule wall. Set these aside <strong>for</strong> several hours until theGoop is dry.3 -3/4”3/16”1/8” hole”#8 AWG aluminum wireFigure 4. <strong>Parasitic</strong> element assemblyNext make the driven dipole assembly. Please see Figure 5. Gently tap the PVC insertconnector into the two pieces of aluminum tubing with a mallet or hammer until they arespaced ¼” in the center. The overall dipole length should be 12-3/8”. Then, drill a hole <strong>for</strong> a#6 screw, 3/8” from end of the tubing at the center insulator. Directly across the insulator,also spaced 3/8” from the end, drill a hole <strong>for</strong> a #8 screw.AMSAT PROCEEDINGS 20069
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