Build a 10 Meter Technician Class
Get on 10
Meters fast with this basic 10 Meter Dipole
This 10 meter
dipole project will enable you to start using your new HF privileges
as a Technician class operator on 10 meter SSB between 28.300mhz and
It is a
half wave dipole designed for the center frequency of 28.400mhz but
should cover most of this 200khz spread with low SWR. This project
shows the 10 meter dipole in the horizontal configuration but may
also be installed in the inverted V fashion.
any dipole is considered a balanced antenna, it should be used with
an air wound choke to help eliminate rf on the coax. See the
"Ugly Balun Project" for
instructions on how to build one from coax.
Building the 10
meter dipole is very easy and simple construction is used with very
inexpensive materials you may already have laying around the shack.
See drawing below:
It consists of 2 equal lengths
of #12 or #14 wire insulated in the center and on each end and
supported with rope, nylon cord, etc from both ends and the center
insulators can be homebrewed from any non-conductive material that
will withstand the rigors of mother nature such as glass,
plexiglass, painted wood, pvc, heavy plastic, commercially made
insulator actually can be used as a duel purpose device, both for
support at the center and to prevent the two outer radiators from
touching. It should be made heavier and a bit larger to handle
the weight of the entire antenna, coax and support ropes. Remember
that it contains all connections to the antenna and some method must
be used to secure them from separating from each other due to wind
load, etc such as plastic wire ties to eliminate strain on the coax
The center support rope at the insulator may not be
needed depending on how much the completed assembly droops when put
up between the end supports. Don't suspend it
between trees unless some
method is used on the ends to prevent
tension from breaking the wire if the wind
It is fed with
standard 50 ohm coaxial cable, from the center of the dipole with
the center conductor attaching to one side of the dipole and the
shield of the coax to the other side. The type of coax is up to you
but the larger coax like RG8 will give a bit less loss depending on
feedline length. The coax should come away from
the dipole at a 90 degree angle to the wire if at all possible when
tuning and in the final installation.
It does not
matter which side is connected at the coax just as long as neither
side of the antenna is shorted to the other side, hence, the
insulator in the middle. Seal all connections at the coax
end where it connects to the antenna including the end of the
coax. This keep water out.
From the antenna, the coax should go
to an air wound choke AT the antenna as mentioned above using
the same coax that would go to the transmitter.
NOTE: Rather than have connectors at each end
of the air choke, just make the feed line coax about 18 to 21 feet
longer than needed to reach from the transmitter to the antenna and
then wind your coil on the form and attach to the
Here is the
standard formula used for half wave dipoles that you should already
know and it is used for the overall length of the radiating
NOTE! It is always better to start LONGER with each
half of the dipole than the formula results below!
antennas will perform the same in all locations with the formula! It
is much easier to cut than add wire to a dipole.
freqmhz = total length in feet:
28.400mhz = 16.478 feet (total length end to
end in feet)
16.478 feet to about 17 to 18 feet total length,
end to end, for swr tuning.
Don't forget to feed it
in the exact center giving you 2 equal legs on each side of the
Do not attempt to tune the antenna on the
ground! It must be raised to it's final operating height for
tuning! If you have an MFJ 259B analyzer or equal, your tuning will
be much quicker and you can do it off the air!
After you have
built the antenna, raise it to the final operating height, (the
higher the better), tune your transmitter to 28.400mhz, listen for
unused frequency and using the AM, CW or tune mode with very little
power, (just enough to get a reading on your SWR meter), transmit
your callsign and say testing; (here again assuming you have a
clear frequency)......immediately check SWR, say you're call sign
again and "Test clear, unkey, trim short equal amounts from each
end, again listen for unused frequency, and repeat on the air
"Testing" with your call sign, keyup, check SWR again, unkey, repeat
as needed for lowest SWR on 28.400mhz so you will be centered in the
Tech portion of the band.
Once you have
tuned it for lowest SWR, make certain you have all supports firmly
tied down and your ready for some fun on 10 meter
Added notes of
If the dipole
is installed in a horizontal (flat top) fashion, it will tend to be
bi-directional, meaning that it will transmit and receive equally
well at 90 degrees (broadside) to the antenna and very little off
A more popular
method of installing it is in the inverted V fashion which will
yield you a more omni (all direction) pattern. You will have to
compensate with the swr tuning using this method as it may be
different from horizontal mounting.
inverted V, simply have the center higher than the ends, like an
upside down V. Don't bring both ends together. Use about a 45 degree
angle from the center insulator.
The dipole has
no gain compared to a yagi (beam) antenna. The dipole is used as a
reference antenna for comparison of other types of antennas and is
usually referenced as 0db gain or in techincal terms 0dbd. The "d"
at the right side of 0dbd represents the
reference (dipole). It is a standard, basic antenna and the
most widely used of all antenna types. A
reference to a dipole is much more realistic when comparing
Until the 11
year sunspot cycle starts to climb, activity on 10 meters (DX) will
be very difficult and limited.
The band will
be most active during the daylight hours (when it is
"open"), but very good "local" contacts will be made using
ground wave coverage anytime, so don't expect to set the world on
fire until the 11 year cycle really starts to climb! Then the world
will open up to you with stations from around the
When the sun
spot cycle is at it's peak, it is very common to work around the
world with 5 watts SSB using a 10 meter dipole!
More about dipoles!
A dipole antenna is a
straight electrical conductor measuring 1/2 wavelength from end to
end and connected at the center to a radio-frequency (RF) feed line
that is connected to the transmitter/receiver.
also called a doublet, is one of the simplest and most
basic types of antennas, and makes up the main RF radiating and
receiving element in various sophisticated types of antennas.
The dipole is inherently a balanced antenna, because it is
bilaterally symmetrical or contains equal conductors on each
side of the feed point.
Ideally, a dipole antenna
is fed with a balanced, parallel-wire transmission line. However,
this type of line is not extremly common and it's impedance does not
match the output of most ham transceivers. It is extremly low loss
however, and due to this fact, it is often used by hams and can be
matched to most 50 ohm output radios. This is usually done with a
matching transformer called a balun, which is a contraction of the
words "balanced" and "unbalanced".
An unbalanced feed line, such
as coaxial cable, can be used, but to ensure optimum RF current
distribution on the antenna element and in the feed line, a
balun should be inserted in the system at the point where
the feed line joins the antenna.
How high should it be in the air?
performance, a dipole antenna should be at least or more than 1/2
wavelength above the ground, the surface of a body of water, or
other horizontal, conducting medium such as sheet metal roofing. The
antenna should also be at least several wavelengths away from
electrically conducting obstructions such as supporting towers,
utility wires, guy wires, and other antennas. This is very difficult
to do with most ham installations.
Dipole antennas can be oriented horizontally,
vertically, or at a slant. The polarization of the electromagnetic
field (EM) radiated by a dipole transmitting antenna corresponds to
the orientation of the element. This means that if the antenna is
installed with it's wire horizontal to the ground, it radiates a
horizontally polarized field. If it is installed in a vertical
position, then it would be said to have a vertical polarized field
in reference to the ground. When the antenna is used to receive RF
signals, it is most sensitive to EM fields whose polarization is
parallel to the orientation of the element.
The RF current in a
dipole is maximum at the center (the point where the feed line joins
the element), and is minimum at the ends of the element. The RF
voltage is maximum at the ends and is minimum at the
The RF current portion of the antenna is where the maximum rf
field is radiated.
To learn even more about
antennas in general, it is highly recommended that you get a copy of
the ARRL Antenna Book seen below!
Enjoy and welcome to the
world of HF....73