THE ALL BAND HF
project will get you up and running with an all band Hf
antenna using one of the oldest and least expensive ham antennas
around.....the all band doublet. If you've got some TV twinlead or ladder
line laying around and an antenna tuner, some wire, insulators and a
bit of time then read on.......Project also includes a novel way of
getting the rf to and from the shack using coax rather than ladder
ALL BAND DOUBLET
Shown using 450 ohm Ladder
Shown with standard TV type 300 ohm ribbon line
The all band doublet
antenna is nothing more than a 1/2 wave dipole cut for
your lowest operating frequency and fed with twinlead, ladder line,
open wire, etc to a tuner that will accept a balanced line connection.
IT IS NOT FED WITH COAX!
It can be designed
for use from 160 thru 10 meters very easily using the standard 1/2 wave
total length (ft) end to end
The exact length is not
If you don't have room for the 160 or 80
meter version...then design it for 40 meters and up! Just remember,
don't operate it on a lower frequency than it was designed for...tuner
damage may result! You can always tie the two ends together at the
tuner and use it as a random wire antenna with the tuner and it
may tune lower bands than it was designed for! Always check swr at low
power before attempting.
It can be installed in the horizontal fashion
or inverted V style. Get it up as high as possible and have
Remember when working with twinlead
(Flat TV feed type) don't use over about 100 watts of power to be safe.
For higher power, use the heavier, ladder, open or window
you have determined the total length of the horizontal section of the
antenna, lay that amount of your antenna wire out and cut it in exactly in
half. This will give you two identical lengths for each half of the antenna. It is suggested that
you use #14 or #12 gauge wire. You can use smaller size wire but it will
tend to break easier with longer antennas due to weight of ice, snow,
birds, wind loads, etc.
The Center insulator/strain
Attach a center insulator between
the two lengths of antenna wire. This center insulator can also
provide strain relief for the twinlead, ladder line, antenna
wire etc. Leave enough bare wire from each half of antenna
wire exposed for soldering to the feedline and for strain relief at
the center insulator. See example drawing below:
Using the drawing above as one example, the center
insulator can be made from any non-conductive material such as sealed wood
or Plexiglass, standard commercial insulators, etc. Use your
imagination and ham engineering. It should be of a size that will allow
the antenna wires to be attached to it from each half of the antenna with
strain relief for each wire including the feedline. Your feedline
also needs strain relief. It can be provided by using nylon ties going
thru the center insulator (drill holes) and tightened on the other side so
as to press the feed line against the center insulator. In the
drawing above, they are the heavy black lines going across the twinlead.
If you use TV type twinlead, this will be a must. TV twinlead is very
fragile and can break easily from too much strain. The weakest point on
the twinlead is where the conductors come out of it on the ends. The wires
are very small inside and break easily.
Each half of the antenna
can go thru holes drilled into the center insulator....use at least two
holes on each side of the center insulator as in drawing...make certain
there are no sharp angles on the edges of the holes to cut the
wire. Thread each side of the antenna wire into the first
hole near the side of the insulator and out the back....then
back thru the other hole leaving enough wire to work with in soldering to
the feedline. This type of arrangement provides some strain relief for the
antenna wires using the mechanical pressure of the wire against the center
insulator. It is important that there are no sharp edges where the wire
enters or exits the holes. Use whatever method that works best for
The two bare wires from each half
of the antenna are attached (soldered), one at a time to each side of the 2
conductor twinlead, ladder line, etc. (Meaning one side of antenna to one
conductor of feedline and the other side of the antenna to the other
conductor of the feedline.) Do not connect all together in the
You should end up with 2 continious conductors side by
side with one continious conductor from the very end of one half of the
antenna to the very end of your feedline at the tuner and the same thing
with the other half of the antenna. Do yourself a big favor and do not get
in a hurry and just twist the wires together at their junctions! They will
soon corrode at the twist and create more problems for you than the time
saved by not soldering them together! Believe me, it will take much more
time in the long run to do it poorly than to do it properly with
solder. You should provide some sort of weatherproof sealer to the solder
joints after you are done soldering...and as a last resort...tape well and
then tape again. If you "cut corners", sometimes a "temporary"
installation tends to become permanent when forgotton about......then
later it will remind you when it does not work!
Attach end insulators to both ends of
the antenna. Attach the insulators to their supports with UV
resistant rope, cord, etc and make sure you have enough to extend to the
outside support tie off points. As a further note for
those that are not experienced with wire antenna building, there are many
ways to build center and end insulators. Do a search on Google.com using
their "images" section for more ideas.
Now assuming that you
have plenty of feedline to run from the final operating position up in the
air for the antenna after raising it.......get help if needed....tie off
the end supports.....run the feedline away from the
antenna preferably at a 90 degree angle and keep the feedline several
inches from any metal conductor such as rain gutters, down spouts, metal
house siding, metal windows, etc. With
very long antennas, the weight of the wire and feedline, center insulator
etc, causes some sizes of wire to sag in the center. If this is the case
with yours, some support in the center may be needed by attaching
another support rope to the center insulator.
(Another option for
the center insulator/strain relief would be to take the feedline and wrap
it OVER a "dog bone" type (round), insulator and then back
down parallel with and touching the feedline making sure you
have a couple of inches left over for attachment of the bare
wires from the feedline to each half of the antenna. Then
use nylon ties to secure it tightly against the main feedline.
wraping the feedline over the insulator and securing it to the
feedline below the insulator, you will be adding a strain relief to
help prevent the weight of the feedline from tearing apart the
After your antenna is up and secure....attach
the feedline to your tuner's balanced output connectors....and you're
Use your tuner as per mfg's
Added notes of information"
are many methods of "hanging" an antenna like this one and various center
supports can be used, like towers, metal pushup poles (masts), etc. The
use of a small cross arm made from heavy PVC or other insulated
material extending out a couple of feet or more from the tower
or metalic pole will help to prevent the feedline or radiating parts of
the antenna from touching any metal and shorting out. This also helps to
prevent the feedline from rubbing against anything in the wind and
eventually coming apart at that
When bringing the feedline down from the antenna to the
radio, always keep it away from sharp corners that can cut it due to
rubbing in the wind.
If you have a shingled roof, try to keep the
feed line away from any edges that (from rubbing) will eventually cut into
the feed line.
Remember to keep the feedline away from any metalic object
by several inches.
Below is a very handy way of gettng it into your radio room
by going thru a window, metal wall, etc.
LADDER LINE OR
TWINLEAD SHACK ENTRY OPTIONS
Note: in the options in the
drawing, the 4:1 balun is NOT used if your tuner already has a
balanced output. Only use it if your tuner does NOT have balanced line
connections. In option #2, the balun would go between the feed line and
the tuner if the tuner does not have a balanced output.
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