The Antenna-Tripod Coupler (ATC) is a handy device that enables the radio amateur to use a camera tripod as a makeshift mast for a a vertical antenna. Tripods typically come with one or two mating pieces that fits onto the top part of the tripod. The mating piece has a small machine bolt that fits into the base of a camera or camcorder. The camera-mating piece assembly then fits into a slot on the top of the tripod.
The ATC uses the mating piece and some additional hardware to mount a vertical antenna on the tripod. The following are needed to build an ATC:
Materials
- Circular junction box (1)
- Circular junction box cover plate (1)
- 2-inch SO-239 barrel (1)
- 1/8" X 1" machine bolt (2)
- 1/8" X 1.5" machine bolt (1)
- 1/8" hex nut (5)
- Washers (1/8" inner diameter, 2)
- Coax cable with PL-259 connector (RG-8X or RG-58)
Tools
- Electric drill
- 1/8" drill bit
- 9/16" drill bit
- Pliers or adjustable wrench
- Screwdriver (Slotted or Philips, depending on the type of machine bolts obtained)
- Vise or C-clamp
Building the ATC
Initial Preparations
Junction Box/Mating Piece
First, drill a 1/8" diameter hole in the base of the junction box; use the vise or C-clamp to hold the junction box in place. Remove the original machine bolt from the tripod mating device. Place one washer on the 1/8" X 1.5" machine screw, making sure it rests on the head of the bolt. Insert the 1/8" X 1/5" machine bolt into the mating device with the head facing down and the open threaded end facing up. Insert the bolt into the hole on the base of the junction box. Place the second washer on the bolt, then place the hex nut onto the bolt and tighten to a snug fit.
Some junction boxes have tabs that can be pushed out to insert wires. If your junction box is of this type, push out one or more of the tabs so the PL-259 connector fits through the opening. If the junction box lacks these tabs, drill a second hole using a 9/16" bit, then insert the coax cable, PL-259 end first.
Cover Plate/Barrel
The hole in most cover plates are 1/2" diameter, which is a near-perfect fit for SO-239 barrels. If a wider hole is necessary, use the 9/16" drill bit to widen the existing hole. Hold the plate in place using the vise or C-clamp. Place two hex nuts on each of the 1/8" X 1" machine bolts, making sure they are threaded up to the bolt heads. Insert the bolt assemblies into pre-drilled holes on opposite sides of the cover plate.
Assembling the ATC
Connect the coax cable to the cover plate by inserting the PL-259 cable end into bottom end of the SO-239 barrel, then gently pull the cable until the cover plate meets the junction box. Rotate the cover plate until the holes on the cover plate line up with the corresponding holes on the junction box. Once line up, tighten the two machine bolts for a snug fit.
Setting up the Antenna
Mount the ATC on the tripod by inserting the mating piece into the slot on top of the tripod. Attach the antenna to the top end of the SO-239 barrel. The two bolts connecting the cover plate to the junction box may be used to attach counterpoises or ground radials, if necessary. Finally, connect the other end of the coax cable to your radio and you're ready to go on the air!
