View Single Post
  #8   Report Post  
Old January 17th 06, 08:05 PM posted to rec.radio.amateur.antenna
F4DRH
 
Posts: n/a
Default Dipole and Ladder Line Matching

Hi Jimg,

Do not bother about the antenna impedance if you want to use it as a
multi-band antenna because it will change a lot with the frequency band.

1) First, install a dipole 2 x D, D being the higher length that can afford
your backyard. (2 x 20 m is good for 80m band operation)
http://www.barbaxoops.com/modules/xc...=7&pos=4&pid=4

2) Then you install the ladder (in the middle of the dipole). The ladder
should go straight from the center of the dipole to the antenna tuner (in
the shack). The ladder can be made of electric wires and PVC pipes as
spacers (do not forget to glue them)
http://www.barbaxoops.com/modules/xc...&album=7&pos=5
http://www.barbaxoops.com/modules/xc...&album=7&pos=2

3) Finally, you built an balanced antenna tuner. The F3LG type is the
easiest to built. The MacCoy (see the following pictures) is the most
popular
http://www.barbaxoops.com/modules/xc...&album=7&pos=0
http://www.barbaxoops.com/modules/xc...7&pos=1&pid=47

.... as you know, that antenna is called a "Center Feeded Dipole" .... but
french people say "Antenne Levy"

Contact me if you want more details about it.

Best regards

Jean-Marc
F4DRH
www.barbaxoops.com









Hi. I've heard and read some about ladder line and dipoles.
So what is the basic configuration look like? My impression is
the set-up starts with either a balanced tuner with 400 ohm output
or a 50 ohm tuner with a 4:1 balun to the 440ohm ladder line. The
ladder line then runs to the dipole and that's pretty much about it.

So my EZNEC on my future backyard Vee shows about 60ohm which is about
a 12:1 mismatch at the antenna feedpoint! So do I have something wrong
in the basic config? Or do you all put a balanced impedance
transformer up at the antenna feedpoint?

Just a little confuzed?


jimg
Oregon
USA