[Antennas] Re: "J" poles

2002年7月11日 18:01:20 -0700

At 11:06 PM 7/11/2002 -0400, you wrote:
>Hi Danny, K6MHE:
>><
>A conventional j-pole is an end fed =BD-wave mono-pole. All mono-poles=20
>regardless of length must work against something.
> >
> Check this again, a half wavelength long antenna,
>no matter how it is fed is a dipole. (and requires no counterpoise)

Okay if you're feeding one end of you are calling a =BD-wave dipole where do=
=20
you connect the other end of the transmission line. I've never seen=20
Kirchoff's laws violated. So where is the return path for the loop=20
current? Please show me in any reputable published document where and end=
=20
feed single element antenna is called a dipole regardless how long is.
As another poster said earlier a j-pole is nothing more than a Zepp antenna=
=20
which is true. A Zepp is an end feed =BD-wavelength antenna it is not a=
 dipole.
Further if you were to remove the =BC-wave matching section and mount the=20
=BD-wavelength element on the ground is it a dipole or a monopole? It is a=
=20
monopole. That what the engineers call it. And it is still a monopole if it=
=20
is elevated and has a radial ground plane. It is also monopole when=20
attached to a =BC-wave matching section. The =BD-wave element current=20
distribution hasn't changed just the method of matching and/or feeding it.
><
>The sleeve matching section is the best way to go and produces the best=20
>omni-directional azimuth pattern. However, have you measure or modeled you=
=20
>elevation and azimuth patterns for j-pole with the *bent* stub? If you=20
>did you'll find that it is not truly omni-directional and the azimuth=20
>pattern will be skewed with maximum azimuth gain in the direction that the=
=20
>stub is bent.
> >
> Yes, but the radiation from the matching sub is polarized 90 degrees
>from the main radiator so the received field strength from the stub is=20
>negligible.
>The effect of the stub near the high impedance end, effects the dipole,=20
>but the
>perturbation is minor IMMHO.

Again, if you were to analyze the antenna more closely you would see that=20
the =BD-wave element is working *against* the bent section (this can be=20
easily verified by computer modeling) and the azimuth pattern will be=20
skewed in that direction. Can you point anywhere in the say ARRL antenna=20
book, or any accredited text book for that matter, were is says that *no*=20
radiation takes place from the =BC-wave matching section of a j-pole?
Regards,
Danny, K6MHE