I wrote:
"A 3 M diameter has about 9.42 M circumference so becomes effective as
its circumference is about one wavelength or about 11.8 MHz. At lower
frequencies radiation from a helix is radial rather than axial."

Rounding:
300/10M=30 Mhz.
Likewise:
300/1M=300 Mhz.
If Art`s helix is only about 1 meter in circumference, not 10 meters, it
will only be effective as an end-fire antenna above about 300 MHz, not
30 MHz. The good news is that his reflector can be proportionally
smaller.

Best regards, Richard Harrison, KB5WZI