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6 METER 6 ELEMENT SSB YAGI PLANS FOR 6 METER SIDEBAND
FUN
This 6
element yagi was designed using the free
Yagi Antenna Design
program by WA7RAI called Quick Yagi (QY4)
This 6 meter 6 element SSB yagi
was designed and optimized for best feed match using 50.125Mhz as the
center frequency which is in the SSB portion of the 6 meter band.
According to the program, it has a gain of 11.06dBi with a front
to back (F/B) ratio of 30.12dB on a boom length of 17 3/4 feet
with 1/2 inch elements using a standard direct feed dipole driven element insulated from
the boom.
The QY4 design program indicated that the VSWR is flat at the
design frequency of 50.125 (1:1), and at 49.49mhz, 1.47 : 1 and 2.22 : 1
at 50.752mhz.
It should be noted that the numbers quoted above came
from within the perfect world of the computer program and not from
the real world that an antenna exists
in.
No matching device should be required as it
was designed to be direct fed with 50 ohm coax, but due to variations
in your construction practices, some adjustment of the driven element
may be needed or us a gamma match with non-split (not insulated from boom)
solid dipole driven element and tune for best SWR.
When checking SWR,
place antenna with reflector on the ground and prop yagi straight up at a
ninety degree angle to earth....use low power to check SRW.....adjust
match or length of driven element as required and recheck.
Repeat procedure until lowest SWR is obtained and mount yagi on your mast,
pole, tower, etc in a horizontal position relative to the ground
for 6 meter SSB operation.
The SWR in the final operating
position may vary slightly but not enough to worry about.
The
measurements on the picture below may be very hard to obtain perfectly,
but don't worry too much about them! Try to get them as close as possible
using whatever construction practices and genius you can find. Round them
off to next highest or lowest number and forget about them.
Lengths for elements:
|
Reflector |
9.77 feet = 9 feet 9 1/4 inches |
|
Driven |
9.53 feet = 9 feet 6 3/10 inches |
|
Director 1 |
9.16 feet = 9 feet 1 9/10 inches |
|
Director 2 |
8.77 feet = 8 feet 9 1/4 inches |
|
Director 3 |
8.85 feet = 8 feet 10 1/5 inches |
|
Director 4 |
8.38 feet = 8 feet 4 1/2
inches |
Spacing between elements:
|
Ref |
3.38 feet = 3 feet 4 1/2 inches |
|
Dir 1 |
2.36 feet = 2 feet 4 3/10 inches |
|
Dir 2 |
4.10 feet = 4 feet 1 1/5 inches |
|
Dir 3 |
3.46 feet = 3 feet 5 1/2 inches |
|
Dir 4 |
4.42 feet = 4 feet 5
inches |
Total boom length = 17 3/4 feet (1 inch metal
boom)
(Refer to Drawing Above)
Get your lengths as close as
possible
Perfection
is best......... but hard to get in the homebrew environment!
The
driven element (dipole) shown in the inset in the drawing is insulated
from the boom which is metal, by the homemade non-conducting bracket which
you must fabricate. Heavy Plexiglass works fine as long as it is thick
enough to support the driven elements (one on each side). Other materials
may be used to construct the insulator as long as they insulate both halfs
of the dirven element from the boom.
The two halves of the total
driven element length can be attached to the insulator using muffler type
clamps, u bolts, several large wire ties or what ever your gray matter can
come up with as long as the elements can not move by outside forces and do
not touch the boom after final installation.
The other elements of the
antenna should be installed thru the boom but if this is
not possible for you, just mount them at the required spacing using your
genius. The final pattern may be slightly off center from the boom by a
degree or two but us it anyway.
The idea is to have FUN and
experiment!
The conductors from the feedline (50 ohm coax) are attached
as you would any dipole. Center to one side, shield to the other using
whatever arrangement of nuts and bolts you may have. Seal all connections,
coax end and antenna elements from mother nature!
If you decide to use
a gamma match instead of this type of mounting arrangement for the dipole,
you won't have to worry about the mounting bracket for the dipole but then
you will have to decide on a way to mount the gamma match.
You can
design your own gamma match for this antenna by using a separate program
that comes with the Quick Yagi antenna design software. Get the free complete download here!
This project was designed to give you a starting point in getting
on the air on 6 meter SSB fun with a respectible signal using just a
stock radio and it should increase your effective radiated power near 9
times (plus or minus a few % for construction
errorrrrrrssssss!
It is also a good idea to use an "Ugly Balun" or other 1:1
balun capable of 6 meter operation near the feed point to help eliminate
rf on the outside of the coax!
EXPERIMENT! EXPERIMENT! EXPERIMENT!
This editor once built a 6 element
yagi for the middle of the 2 meter band using discarded aluminum sections
for the elements that were "U" shaped from old junk flouresant light
fixtures and attached them to a 1 inch square boom, 16 inches apart for
each and the standard dipole formula 468/freqmhz was used for the driven
element fed with a homebrew gamma match. 5% was added for the reflector
length and each director was shortened 5% shorter each, progressing to the
end of the boom!
SWR was checked as above and was less than 2 to1 to
start but was lowered a bit, down to about 1.5 to 1 and put up on a 16
foot mast with rotor and it worked great!
Copyright 2000 - 2006 N4UJW
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