easy quad calculator enter center frequency to get a quad antenna size. This resource is listed under Antennas/Antenna Calculators | Antenna, Antennas, Quad
Building a Cobweb Antenna and Testing it with NanoVNA [with video] ← M0JCQ's Ham Blog
G3TPW CobWebb Antenna for the 14, 18, 21, 24 and 28 MHz Bands
CobWeb Aerial | M0PZT
Cobweb Antenna
M0PZT CobWeb Antenna Project - Resource Detail - The DXZone.com