The Zepp (Zeppelin) antenna trailed in a straight line behind a lighter-than-air airship. It is a half-wavelength long single-wire radiator with its very high feedpoint impedance high reduced to something more manageable by a quarter wavelength matching section (Q section) that is physically in line with the half-wavelength single wire radiator.
Electrically the Q section consists of two parallel wires. One of these wires connects to the half-wave radiator. The other wire looks to be left open at its end, but it actually capacitively couples to space. An unbalanced feedline (coaxial cable) is connected to the other end of the Q section with the center conductor of the coax connected through the Q section to the half-wavelength radiator, and the outer coax conductor (shielded braid) is connected through the Q section's other parallel line that couples to space.
From time to time I see a "center-fed Zepp" antenna mentioned. How is this possible?
Charles (aka Chas), W2SH
Date: Tue, 11 Aug 2015 11:44:13 -0700
Subject: [4sqrp] Re: TEST POST
This is Darryl, KK5IB, from NE Arkansas, on at all hours of day and into night, usually go to bed about midnight CDT. I run mostly CW QRP with my K2 or K3 and a 205' center fed zepp at 30 '. Not too much of a rag chewer, with speed around 15 wpm or a little faster. We could set up a sked to try.