Schubert Antenna Wizard
Joined: 08 Apr 2009 Posts: 161

Posted: Sun Oct 24, 2010 7:28 pm Post subject: 


Well, I can offer my thoughts. At a circumference of one wavelength, the spiral (linear) length will be on the order of a halfwavelength (depending on how tightly or loosely the spiral is wrapped, of course).
Spirals have a lower frequency at which it radiates, and that is when the spiral length obtains a significant fraction of a wavelength. Above this frequency, the spiral becomes electrically larger, and it still radiates, the extra length then just cancels out since the two arms of the spiral carry roughly the same current.
As for the mathematics on this, or references, I don't know. In my opinion, antennas are best understood intuitively. The math tends to be overly complicated and not at all useful for real world antennas. Mathematicians, frankly, don't know anything about antennas. 
