View Single Post
  #3   Report Post  
Old November 18th 04, 08:12 PM
Richard Harrison
 
Posts: n/a
Default

Richard Clark wrote:
"I would suggest you research the "Franklin Array"."

Current reverses at the open-circuit end of an antenna. 180-degrees back
from the open end it reverses again. Current flowing in opposite
directions begins to reduce the field strength perpendicular to the
antenna when the total length reaches 5/8-wavelength.

At a point 1/2-wave or 5/8-wave back from the open circuit, a phase
inverter is used to produce (2) mostly in-phase antenna segments. Some
ways to get in-phase segments are to drive the array at that point. Or,
to connect the segments through a short-circuit 1/4-wave stub. The
"Super-J Maritime Antenna" in the ARRL Antenna Book uses this method.
Or, use a lumped network in place of the short-circuit stub.

Kraus shows an interesting and simple phase inverter in Figure 23-21(b)
on page 824 of his 3rd edition of "Antennas". The inverters are
self-resonant coils. No external capacitors required. They are "traps".

Best regards, Richard Harrison, KB5WZI