50MHz 4 elements HB9CV antenna, Comet replica
Budget 9,000 yen (US$90)

1. pre-face

In the past of '90s, some ham had their own mobile
style with 2 elements HB9CV and there were few hams
who had a bigger antenna for mobile use.
Recently after Comet, a amateur antenna
manufacturer, introduced their 4 elements HB9CV,
such a new mobile style bringing the antenna into
the mobile became very popular among Japanese hams.

2. power of 4 elements

HB9CV. HB9CV is light weighted with good performance
and there are so many funs to use it in amateur
world especially mobile use.
Around 1985 JA1GHP, Mr. Ohno, made some experiments
on the antenna with 4 elements, then some "maniac"
has started using the antenna. It is one advantage
for user of 4 elements HB9CV to get + one signal(S)
strength than normal HB9CV. This means 10W power is
equal as 50W station, so some JA calls it as
"turbo-charged HB9CV". The cons of the antenna is
there are two feed points .

3. off the shelf 4 elements HB9CV.

Comet, a manufacturer of amateur antenna, introduced
their 4 elements HB9CV in reponse to many amateur
voice. The weight of the antenna is 2.1Kg, light
weighted compared to their 2 elements HB9CV, which
is 0.9Kg. The key point for mobile use is "weight"
and "easy to use", so this antenna is highly recommended.
By the way the weight of their 6 elements HB9CV is
6.3Kg. Though the 4 elements antenna has not superb
"gain", but the good location where you operate will
offset it. The light weight is a key to mobile use.

4. let's make 4 elements HB9CV

The base antenna of this 4 elements HB9CV is off the
shelf 2 elements of HB9CV, which is Maldol made. You
can choose any manufacture's 2 elements HB9CV. To
add additional two elements, I choose a slight thin
pipes as boom and elements. I used mast clump on
hand, but you can use what come with the 2 elements HB9CV.

The figure shows size of additional elements. The
diameter of the aluminum pipe is 6mm and 8mm. And
16mm and 19mm aluminum for the boom. I use paper
clips to fix these elements on the boom, it takes
just 5 seconds.

5. manufacture

Cut aluminum pipe as shown in the Figure. Each pipe
should be connected together by self-tapping bolts.
The way of mobile use is just assemble elements with
the boom at destination point, the other part of the
antenna is already assembled. At the point where the
element is fixed on the boom, use 19mm pipe over
16mm pipe and paper clips are fixed by U-bolts.

The key to make good antenna is "lenght of elements" and "space between elements".

6. measurement and finishing.

I moved the short bar position from it's original to
Comet's position. The Figure shows the SWR
characteristics without any adjustment. Between
50MHz to 53.5MHz is practical range to use, it is
very good. The reason why it has two "dip" in the
SWR curve may be the position of the short bar, but
it is not related to it's gain. And finally give a
coat of anti-rust spray on the paper clips.
One tip: use different color on each element, it
will show you which element is which position when
you aseemble the antenna.

7. conclusion.

This antenna is just 1.6Kg, compared to off the
shelf 4 elements HB9CV, which is 2.1Kg. The time to
assemble the antenna is 7 minutes with 8 meters
high. Two pictures show "before assemble" and "after
assemble". Since I made the antenna in 1994, still
it is on the active in my list.

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