There are other types of feed line too, including open or balanced line,
often called twin lead, and hardline in various diameters, to name just a
few.  Hardline is generally used for high power  stations, as well as for
frequencies above 148 MHz.
Also, if the distance from the transmitter to the antenna system is very
long, 200 yards or more say, then hardline is a very good choice.  The
longer the feedline is, the more loss you have.  Though the distance from my
shack to my tower is < 100 feet, I chose to use 7/8 inch diameter hardline,
transitioning to a large diameter type of coax for the vertical run up my
electrically operated crank-up tower, called LMR600.  The result of using
the combination of hardline and large diameter coax, is very, very low loss,
in the range of quarter of 1 DB.  The total length of my feedline from the
shack to the antenna is approximately 200 feet.

HTH

Best 73



Alan R. Downing
Phoenix, AZ


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Michael Thurman
Sent: Friday, August 02, 2013 1:55 PM
To: [log in to unmask]
Subject: Re: question

coax cable, called coaxial because it has a center conductor, and a =
concentric shield conductor,  coax sharing the same axis. It is used =
primarily as a feed line for rf to and from antennas, also between =
components in an audio video system. there are  many different kinds  of =
cable, from the thin stuff that comes with a cheap dvd player to  inch =
or larger feed lines for commercial installations.  There are antennas =
that use part of a coax cable, such as a coaxial dipole, where the =
shield is pulled bak ove itself to form half of a dipole antenna, =
leaving the center conductor and insulation, called the dielectric  as =
half of the antenna., but most commonly it is used as feed line.  You =
might be interested to know that although the shield is one conductor, =
it functions as two conductors at rf  frequencies, which is why it works =
well as a shielded feed line. the rf flows on the center conductor and =
the inside of the shield, not the outside.. that is why you can make a =
could out of coax, or use ferrite chokes to eliminate rf flowing down =
the coax back to the shack.
73 kb7nla
On Aug 2, 2013, at 4:32 PM, RJ Sandefur <[log in to unmask]> =
wrote:

> What is coax? Is that what you make your antana from? RJ