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...
On Jun 10, 3:36?pm, "Kash J. Rangan" wrote:
Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out
of
my shack window but I would like to use a low loss ladder line for the
main
run up to the antenna feed point. Is it OK to place a 4:1 balun just
outside
of the window ?for the transition?

Kash, AG4EL

The G5RV antenna uses a combination of coax and ladder line, so this
type of antenna is in use by 1000's of Hams.

The 4:1 balun is a bad idea for a multiband antenna, due to the
impedances involved at the various operating frequencies. Just
transistion from the ladder line to the coax and use a 1:1 choke balun
at the antenna input of your tuner. You did not mention an antenna
tuner, but you will need one for multiband operation.

In general keep the coax length as short as possible.

Gary N4AST


Another thing to consider is that the length of the 450/300 ohm twinlead
feedline is an important factor when considering the operational bandwidth
of said "dipole" antenna (it's only a dipole when operated at its resonant
length).

The twinlead is utilized as part of the radiating system when operated on
certain bands. This unusual impedance is why the tuner is needed. Shortening
the twinlead and using more coax limits this antenna's ability to operate
over wide frequency ranges. My Van Gordan All Bander's twinlead enters my
shack and then connects to a balun, which is then fed by coax that is
connected to my MFJ-989C tuner. I can often tune down into the 160 meter
band using this setup, though I wish my twinlead feedline length was a bit
longer for even greater tuning flexibility.

By the way, my All Bander also works great on six meters.


Ed, AJ4PJ