Wednesday, February 16, 2011




The diagram and photograph above show an inexpensive compact 3 element beam for 6m. The aluminum pole I used for the boom was obtained from a local shop. The aluminum tubing used for the elements and element to boom mounting clamps came from DEE COMM (suppliers of antenna hard wear for home constructors)

As you can see from the diagram the antenna has a gamma match. It is easy to construct. The capacitor is a length of heavy duty coax with the outer braid stripped off. The insulated inner and wire is inserted into the gamma bar tube. By adjusting the length of the bar sliding the coax inner up or down the tube the capacitance can be changed over a wide range. The coax from the shack is fed to the SO239 connector on the plastic weather proof box.

Because of the gamma match the driven element does not need to be cut in the centre, this makes the antenna stronger and is known in the old days as the plumbers delight.

The antenna has a forward gain of about 6-7dBd. It does not look out of place when on the mast. It could even be installed in the attic as the turning radius is quite small.

No comments:

Post a Comment