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MINI
HORIZONTAL "V" 2 ELEMENT "HAMSTICK" 20M BEAM. by
Russ Wilson, VE6VK
Material
Required: 4ea 20M "Hamsticks" 1 inch diameter boom 4 ft 6
inches long. 1 aluminuum mounting bracket driven element. 1 aluminum
mounting bracket reflector. 4 insulated CB mounting kits 3/8" by 24 TPI
(2 can be un-insulated for reflector. Wire for hairpin match. 14 gauge
electrical wire with insulation removed. Coaxial balun 12.5 ft RG58
wound on a 1-1/4 inch white PVC 8 inches long. Bolts, nuts, lock
washers for mounting.
CONSTRUCTION:
Two aluminum brackets are made out of scrap aluminum 1/16
inch thick or a little heavier if desired. The brackets are bent into
shape as per the photographs to allow element kits to be mounted so the
elements are at 90 degrees from one another. At 15 ft off the ground,
measurements were made of the Driven element using an electrical 1/2 wave
length of RG58 as a 1:1 transformer. Using the antenna analyzer from the
ground the following measurements were noted. Impedance 25 ohms SWR
2:1 The antenna was resonated to 14250 Khz.
A hairpin match was
made using #14 gauge electrical wire with insulation removed. Two lengths
18 inches long are required. (See Arrl Antenna Book for more on hairpin
matching) The two wires have solder lugs placed on them at one end.
These ends are connected to each mounting kit terminal for the Driven
Element. The wires are spaced 1-7/8 inches from each other and are
arranged so they are approximately 1 inch above the boom. See photographs
for details below. A couple of wood or plastic spacers are used to keep
the wires separated. Also a piece of 3/8 inch thick plastic is mounted on
the boom, 2 holes drilled for the wires to pass through for extra support.
After the hairpin is mounted and a temporary shorting bar placed across
the hairpin, the antenna is placed in its original position and further
readings taken, adjusting the sliding short across the hairpin, until the
impedance of 50 ohms is reached. A little juggling of the whips to bring
the driven element back to 14250 Khz is necessary. After a few minutes of
testing and adjustment of the hairpin short and the whips, the resonant
frequency of 14250 Khz is reached and the impedance reads 50 ohms. The
wire short on the hairpin can be permanently soldered.
Measure the length of the whip on the driven element, multiply this
by 6% and add this to the length of each driven element whip. In my case
it was 38.5 inches. 2.3 inches was added to each reflector whip. The boom
length was experimented with and the length shown seemed to be optimum for
the short boom. The reason for the resonant frequency chosen was my own
personal preference as I do quite a lot of operating for IOTA 14260. If
you wish to operate CW or any other preferred frequency you can choose by
figuring out the frequency response of the beam is approximately 200Khz.
The photographs should assist in figuring out the brackets etc. The actual
measurements from tip of whip of each half element to boom.
Driven
1/2 element = 86.625 inches (220.0 Cm) Reflector 1/2 element = 91.75
inches (233.0 Cm) This is
using the regular Lakeview Hamsticks. The PHF type are much better and
you do not have to readjust or mark the whips.
I worked
XZ7A on CW with the beam and 80 watts, so apparently it works. A
frequency run and measured SWR is as
follows:
|
14100
2.5:1 14130
1.5:1 14140
1.3:1 14150
1.2:1 14165
1:1 14202
1:1 14250
1:1 14300 1.1:1 14350
1.4:1
|
 The
finished product!
 The not so
"Ugly" balun

Note the 90 degree angle between element attachment
mounts and the 45 degree angle to the boom of the driven and reflector
elements!

 Pictures above showing driven element detail with
hairpin match attached and insulators mounted on
boom
Many thanks to Russ, VE6VK for
allowing us to share his project with all! Russ not only is a fine
antenna builder, ask him how to catch a fish! Email Russ here for
questions


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