--- In topband-helical@..., "k5est" <k5est@...> wrote:
>
> --
> > I put my work on the net so amatuers could play with it, but Americans
> > take the position that "all is known about antennas and want to buy
> > instead of making things. It would be neat to hear some G's on top
> > band despite the difficulties.
> > Cheers and beers ( brown ale will do)
> > Art Unwin KB9MZ.....xg
> > Stepney
> >
>
> OK Art,
>
> I will take a crack at building up one.
>
> The flatness of the SWR curve concerns me since
> you have close to a radiating dummy load unless
> you are dependent on the feedline to do the
> radiating. The last several small antennas have
> this common problem and when fitted with a proper
> isolation balun at the antenna feedpoint to
> seperate common mode radiation from the feedline
> to the antenna, the antennas were nothing close
> to their claimed performance. Would you please
> address this issue?
>
> 73....Walter - K5EST
>
Walter
The antenna is in equilibrium so there is no radiation from the line.
You can check this out with a optimizer program by obtaining a std
helix antenna and increasing the number of turns upwards and then come
down to the base by winding on the outside. I use magnet wire that is
pre twisted pairs using a drill with 30 ft lengths. Starting with the
middle of this wire I alternatively wind the wire and push it down.I
use a series of pretwisted wire as that makes it easier to wind. When
the winding is done I connect the wires into one circuit which
representd contrawound up and down twice. I then coat it with varnish
and then slide it off of the former where it looks like a lamp shade.
You have to remember that computer programs are derived from Maxwells
law which does not use the coupling method of a yagi so a helix is a
natural classical helix antenna.As far as a dummy load the wire used
will always radiate, you can't stop it from doing that! Bye the way
use cheap telephone wire for your first antenna as mechanical strength
required is zero so you can move close to the fuse point of the wire.
At the moment I am making a sloper for top band using 12 wires
interlaced together and connected into one complete circuit withb the
addition of a variometer. Getting excited with this one!


Cheers

Art