21/28/50MHz three bands whip antenna
(budget 3,500 yen)



You cane hear so many signals in HF high bands,
where you can enjoy domestic QSOs with simple mobile
antenna and 10W. But antenna efficiency is
sacrificed to its simpleness, so in this article I
pursue better efficiency than light


2. rough design.

My car garage allows me to use a car with height of
2.7meters assuming antenna is mounted with a car
aslant. So I decided the maximum length of the
antenna is 2.7meters. And I assume the antenna will
be used during car stop rather than during driving a
car, so it will help to make use of slight larger

The material of the antenna is grass fiber fishing
rod. it is light weighted, though it is rather
thick. At 21MHz, it will operate as 0.25 wavelength
with loading coil. At 10 metere, it is just 0.25
wavelength antenna without any coil. At 6 meter,
only half of element is utilized and it will make it
easy to match. The Figure shows Voltage distribution
along with element.


3. how to make the antenna.

The fishing rod was divided four sections with
length of 3.5 meter, I use only first three sections
of the point. The connector (MP-10) is connected
with these rod, and the length become 2.6 m
including the connector. I use epoxy glue to fix
the connector and rod as well as between each rod.
Use a self tapping screws to fix the connector
firmly with rod. (refer to the Figure)


In the center of the rod, attach a metal fitting
where I can fix a coil. ( See the Figure) This is
made by aluminum or copper and make it curved then
glue them on the rod. Wires from the bottom of the
rod is connected at the metal fitting by a
solderless terminal, wires from the top of the
bottom of the rod is also connected at the metal
fitting same manner. At this point wire should be
fixed temporally so you can adjust later. I use
grass fiber rod with diameter of 5 mm for gardening
to make the loading coil for 21MHz. The both edge
of the loading coil is covered by metal bands made
of copper or aluminum. The coil is 93 turns of 0.8mm


4. adjustment.

To adjust the antenna, it is better to use a
broadband SWR meter, but it is OK if you do not have
such meter.
A. prepare open space.
B. use a car to which you will attach the antenna.

Start adjustment at 6 meter band.

Adjust wire pitch
and length of the bottom side of the rod to get best
SWR at 51 MHz or 50.5MHz if you use it for SSB
operation. If initial length of the bottom rod is
1.35m, I do not think you need much adjustment on
this portion. The best frequency of SWR is slight
higher you expect then the wire turns should be

SWR fig

Next is 10 meter band.

In this band, make short
between the both side of the metal fitting to get
the best SWR on 28.5MHz. When the top side of the
rod is shorter than 2.5m, the wire turns on this
part should be increased. (This means narrower space
between turns to get more turns )

The final is 15 meter band.

At first your make a
loading coil to get the best SWR on 20.9MHz or
around. . Then decrease the coil turns to get the
best SWR frequency on this frequency. At this point
you do not expect the best SWR means near 1.0. In my
case the best SWR is 2.7.



Then attach capacitor hats (CH, in the Figure) to
decrease SWR. But at the same time the resonant
frequency slightly moved to higher frequency. This
is the reason why I adjust the best SWR on 20.9MHz
in previous procedure. It is OK the SWR goes to 1.5
or less within the band.
The size of capacitor hats are, in my case, 10 mm x
110 mm and 10 mm x 70 mm. See the picture. Finally
the best SWR is 1.1 and impedance is 55 ohms.

5. option.

You can try different bands, which is near 21MHz
band, such as 13MHz,18MHz,24MHz just adjusting
turns of the loading coil. But the impedance of the
whip antenna portion is best in 21MHz, so you may
not get near SWR1.0 in these bands.

6. completion.

Apply epoxy glue over the loading coil for
protection, then you may experience the resonance
frequency move to 200KHz lower side. Also apply it
to wires around the rod to fix it.
Compared to other antenna whose top portion is 1.2
m, the signal strength is improved. On 10 meter
band, this is full 0.25 wave length antenna so you
can use the antenna as DX use. On 6 meter, only the
half of the antenna length is utilized, so it
performance is so so.

7. afterthought.


I often use the antenna on 21MHz, but during rain
SWR goes to low (translator comment : something
strange, it should be "SWR goes to high") I attach a
pipe to cover the loading coil. This pipe is also a
part of thick fishing rod, and after cover the
loading coil apply epoxy glue to protect coil from
Also I made an adapter to QRV on 7MHz. See the picture.

7MHz adapter
parts list.
fishing rodmade by grassfiber (3.5m)1
grass rodfor gardening dia. 5mm20cm
copper wire1.2mm or 1.0mm4m
copper wire0.8mm UEW3m
aluminum or copper plate50mm x 120mm1
solderless terminaldia. 3mm4
screw3mm x 10mm2
self tapping screw3mm x 6mm1


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