VHF Big Wheel Antenna

The "Big Wheel" is a horizontally polarized omnidirectional antenna.

Other Big-Wheel 144Mhz

It may seem bulky (1.2m diameter tailored 145MHz antenna) for portable use but can be set to half the height of a metal rod without too much radiation pattern perturbation, which is not the case with a fixed vertical on an offset arm .

One drawback is its relative fragility because its wind resistance is very important. Loaded with ice and subjected to a strong wind it sometimes folds and breaks.

Each of the three leaves of the clover is actually a loop whose length is distributed lambda. The A end of each of the three rings are connected together and the three B terminals are on their side as well.

The coaxial connector (here a N-239) is fixed to the L bracket, its ground is directly connected to the ends A loop. A t-rod is soldered to the central socket (core of the coaxial cable). This barrel passes through the central hole of the disc D to which it is electrically connected via two nuts. The three rings are connected in parallel, so to speak, so the three rings interact on each other.

In the presented industrial model, V screws are used for both mounting the L bracket to the insulating block and the electrical connection between the bracket and end rings. With time and oxidation of bad contacts appear and disassembly-cleaning is necessary.

The only adjustment is to adjust the position of the S stub at the center SWR curve above 145MHz.

Using an antenna analyzer makes the job easier, but this can be done quickly with an SWR meter and transmitter signal.

SOURCE: https://officinahf.jimdofree.com/antenne-vhf-uhf/vhf-big-wheel/