LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #11   Report Post  
Old November 3rd 03, 02:49 PM
Richard Harrison
 
Posts: n/a
Default

Roy, W7EL addressed several provocative questions to Cecil. Anyone can
comment, so I will.

Roy wrote:
"And where those coulombs are going that go into one end of the inductor
and don`t come out the other."

Coulombs travel back and forth in an inductor and may go actually
nowhere. Their movement in an unshielded inductance may result in
radiation and certainly produces some heat.

The purpose of a loading coil in a short loaded vertical antenna is
often to add to the existing degrees of antenna length to reach a
resonant length of 90-degrees, as shown in Fig 9-22 of ON4UN`s "Low-Band
DXing", and included on Yuri`s web pages.

Fig 9-22 is illustrative. First, a full-size 90-degree vertical is
shown. Current is maximum at the base and zero at the top. This is also
true for what Kraus calls a "normal-mode helical antenna". A normal-mode
helical antenna has its principal radiation at right-angles to the axis
of the helix.

The normal-mode helix is fed from a generator with two terminals. One
terminal feeds the base end of the helix directly. The other generator
terminal feeds the ground end of a capacitance between the ground,
various turns, and the tip end of the helix.

The impedance is only a few ohms at the ground end of the helix and
perhaps several thousand ohms at the tip end of the helix. This means a
lot more amps at the ground end of the helix than at the tip end, though
the power flow through the generator`s terminals is the same in either
terminal.

Best regards, Richard Harrison, KB5WZI

 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Inverted ground plane antenna: compared with normal GP and low dipole. Serge Stroobandt, ON4BAA Antenna 8 February 24th 11 10:22 PM
Smith Chart Quiz Radio913 Antenna 315 October 21st 03 05:31 AM
QST Article: An Easy to Build, Dual-Band Collinear Antenna Serge Stroobandt, ON4BAA Antenna 12 October 16th 03 07:44 PM
Eznec modeling loading coils? Roy Lewallen Antenna 11 August 18th 03 02:40 AM


All times are GMT +1. The time now is 09:44 AM.

Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004-2025 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017