Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old July 3rd 07, 01:20 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Apr 2007
Posts: 150
Default Length of Dipole / Inverted Vee with Ladder Line


I think I asked this question before some months ago but can't find it
with google / dejanews and anyway I'm not entirely certain I fully
understood the answer.

I am putting up an inverted vee fed with ladder line and a tuner, that I
want to use from 160 through 10, but mostly on 160 through 40.

The space I have to put it up is large enough for a half wave on 160
and then some.

Since I am feeding with ladder line and a tuner, is there a particular
advantage to cutting the antenna as a half wavelength on 160, or would I
be just as well off to make it as long as I have space for without
considering its actual resonant frequency?

  #2   Report Post  
Old July 3rd 07, 03:33 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default Length of Dipole / Inverted Vee with Ladder Line

Rick (W-A-one-R-K-T) wrote:
Since I am feeding with ladder line and a tuner, is there a particular
advantage to cutting the antenna as a half wavelength on 160, or would I
be just as well off to make it as long as I have space for without
considering its actual resonant frequency?


Fed with ladder-line, there is no particular advantage to
making the dipole 1/2WL long. If the feedpoint impedance
is 50 ohms, the SWR will be 9:1 on 450 ohm ladder-line.
The impedance seen by the tuner will be some transformed
impedance associated with that 9:1 SWR and can range up
to 4050 ohms if the feedline length is 1/4WL. I personally
like to feed a 75m 1/2WL dipole with 1/2WL of ladder-line
to duplicate the antenna feedpoint impedance at the tuner
but that results in an unwieldy ladder-line length of
233 feet on 160m.

In fact, one popular length for 160m is a 204 foot dipole
center-fed with 60-100 foot of ladder-line. With 60 feet
of ladder-line, it is known as the double-sized G5RV. With
60+ to 100 feet of ladder-line, the impedance seen by the
tuner on 160m is fairly low with some inductive reactance.

Another consideration for dipole length is the EDZ length
frequency. If you divide 1200 by the length of the dipole,
you will get the EDZ frequency in MHz. Above the EDZ
frequency, the radiation pattern breaks up into multiple
lobes with a smaller amount of broadside radiation. The
free demo version of EZNEC will predict the radiation
patterns.
--
73, Cecil http://www.w5dxp.com
  #3   Report Post  
Old July 4th 07, 07:49 AM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Dec 2006
Posts: 1,169
Default Length of Dipole / Inverted Vee with Ladder Line

"Rick (W-A-one-R-K-T)" wrote in
news

I think I asked this question before some months ago but can't find it
with google / dejanews and anyway I'm not entirely certain I fully
understood the answer.



Reply
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
Optimum length for ladder-fed dipole Rick Antenna 11 February 6th 07 05:08 AM
Dipole and Ladder Line Matching jimg Antenna 7 January 17th 06 09:05 PM
Feed Line Length - Ladder Line Pat Whelton Antenna 10 July 7th 05 12:54 AM
Coax Length for G5RV and Center Support for Ladder Line ? Gary Antenna 10 April 25th 05 02:27 AM
Length of ladder wire for G4RV "Junior: antenna jim Antenna 0 March 3rd 05 04:08 PM


All times are GMT +1. The time now is 04:19 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017