The tripods play the role of the ground for the vertical antenna (short vertical fixed with red tape on a plastic PVC tube) located at the tip . This geometry is not tuned for any frequency, it is presented here for illustration purposes. Vertical and tripod elements are from aluminium.
For now, see a preliminary construction of my prototype tripod antenna above.
Some of the properties of my design include:
- Only 3 drill holes are required! (one for each radial)
- Cheap to construct
- Portable and foldable
- Extremely quick to assemble and disassemble when needed
- Stable design
- Easy to install: just open up the radials and fix them down to the ground or any other surface
- Vertical element tunable: The vertical element can be adjusted by shifting it up or down to adapt to the desirable frequency
- Radials’ angle tunable: simply unscrew, adjust, screw again and you’re ready! This will help you adjust input resistance and match it to your conditions
Some details about the photos below:
- There is a supporting PVC tube (white in colour on these photos). This tube is used to attach the vertical monopole (made of aluminium). Then the PVC tube is attached with a metallic base, ‘star’ shape, which has 3 aluminium elements attached each with the ‘star’ using a screw.
- The ground of the coaxial cable is tight between the PVC tube and the metallic ‘star’. The inner conductor of the coaxial is attached with the vertical monopole using a metallic collar.
- On these photos the following dimensions were considered:
- Vertical monopole: 12mm diameter, around 17cm long.
- Diameter of plastic PVC tube: 40mm. Length not critical, it depends on how well you want to support the vertical monopole with the PVC and stability.
- 3 legs (each): 1.25m long, rectangular cross-section 20mm x 20mm. You can obviously try circular cross-sections, but for the shake of this project I used these as I didn’t have anything spare around.
Please, note, that I haven’t tested this antenna on these dimensions, it’s perhaps innapropriate for any contact. You will need to cut the lengths of the vertical and the 3 legs according to your requirements and band. I am trying to give you the idea of how you can make an antenna which is portable, easy to carry around, easy to adjust/tune/modify and cheap to construct.
Update (30/10/2015): I have now constructed this antenna for VHF operation. See my post here for details.
Above: The vertical 3 element tripod prototype antenna