Virgil Smith wrote:

...

Sometimes, all you need is one page ...

http://www.untenna.com/tech.html

Especially interesting is:
Building the helix from tubing instead of fine wire reduces conductor
resistance, increases its bandwidth and gives it a rigidity that makes a
plastic support unnecessary. Figure 4 shows a helix design. With the use
of a big diameter winding and a shunt feed, the top hat and matching
networks are not needed. The use of tubing, a large diameter and a shunt
feed reduces conductor losses to a point where the short helix’s
efficiency exceeds that of loaded whips. The helix’s rigidity eliminates
signal strength variations that may be caused when whips flex.

The above taken from the page ...

Regards,
JS