LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #13   Report Post  
Old May 30th 09, 05:06 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Apr 2008
Posts: 543
Default What's the Dealio with the J-pole?


"Jim Lux" wrote in message
...
John KD5YI wrote:
"JB" wrote in message
...


The 1/4 wave ground plane has a useless pattern. Main lobe at about 30
degrees above horizon, but broad enough to be usable and simple to

build.


The quarter-wave antenna's height above ground has much more to do with
the elevation angle than the fact that the antenna is a quarter-wave
ground plane. Using EZNEC, I see that a quarter wave antenna situated 3
wavelengths above real/high accuracy ground of medium characteristics
has a main lobe 4 degrees above the horizon. At that angle, the gain is
5.1 dBi. You can confirm this if you have a copy of EZNEC.

John


If you're just looking for a portable vertical antenna, just a wire on
the end of the coax, and hanging it up, works pretty well. The shield of
the coax (outside surface) serves as the other half of the dipole.
Heck, it will have a bizarre pattern, and couple RF everywhere, but
you're talking about an antenna you're hanging out of a hotel window or
something.. You're not doing earth-venus-earth radar tests... you're
just getting the antenna away from where you are sitting to "outside"..


If you are using such construction, why not just build a coax type of
colinear? It isn't so difficult to add a section of outer shield for
decoupling. Have you priced PA hybrids lately?

BTW any degree uptilt is usually worthless unless you are deliberately
limiting coverage to the horizon. and anything significantly higher in
elevation is line of sight anyway. For ground level base station or
repeater that covers a localized area, a J-pole is attractive because of its
broad pattern that allows numerous reflections through and between the
buildings. I've been told that an upside down ground plane ought to work
better, but it doesn't

 
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
J-pole 144/432 Radio Vintage Antenna 4 August 14th 07 04:22 AM
J Pole Amerigo Vespucci Antenna 4 September 9th 06 07:24 AM
J Pole [email protected] Antenna 4 July 16th 05 01:25 PM
J Pole for 40 Richard Antenna 2 September 20th 04 09:12 PM
6m J pole Barry Antenna 4 July 14th 03 08:04 AM


All times are GMT +1. The time now is 01:50 PM.

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