EL CHEEPO BEAM - The Hardware
store Six-shooter (3 element yagi)
Build this beam for under 20.00 and get 8.5 DB GAIN on SIX !!
Ok time to get out the calculator and spend 3 hours
figuring out your next beam...
Just kiddin'. If you have three or four hours to play and a rig that
can run on 6 meters, this article will make you loud and proud with
no more than 100 watts.
First, hit your local Lowes...or Home Depot, they
have all you need to build this beam and you may have a few items in
your junk box that will help you along the way...
Parts Order:
(3) 10 FOOT 1/2 IN. Galvanized Electrical Conduit (or equivalent) -
$2.25 each
(1) 10 FOOT 1 1/8 IN. Galvanized Fence Post 18 GAUGE STEEL (or
equivalent) - $9.18 each
NOTE: You can use just about
anything for the boom. It must be 96 INCHES in length (8 foot).
(1) 4 FOOT length schedule 40 - 3/4 OD Vinyl white plumbing pipe.
(or equivalent) $2.19 each
NOTE: This is the COUPLER for
the DRIVEN ELEMENT DIPOLE SEPARATOR.
(1) 1/8 INCH by 36 INCH piece of COPPER or BRASS ROD. Copper = $1.80
- BRASS = $2.09 each depending.
NOTE: These RODS are available
at WELDING SHOPS, HARDWARE STORES or HOBBY SHOPS.
(3) Hardware clamps for mounting the elements on the boom. One must
be INSULATED from the boom.
NOTE
Miscellaneous hardware to put the beam together. I will show you how
I did this and you can follow along as needed. This is not hard to
do and no fancy hardware is required. I will show you a couple of
ways you can do mount the elements. You can even weld the beam
together if you have a small MIG. At this price who cares ?? You
can't get a case of decent beer or a carton of smokes at these
prices.
Did you get the list ?? Did you look in your junk box ?? I bet there
is a lot of neat stuff in there that will help you build the "Six
Shooter"...
Now the dimensions:
This is a 3 element beam and like most the DRIVEN element is closer
to the REFLECTOR than the DIRECTOR, thus the name "WIDE-SPACED".
Most low-ball 6 meter beams are NARROW SPACED and are designed to
take up little or no room. They are GAMMA MATCH and very weakly
built at that. Some use SOLID ROD ELEMENTS that are 3/8 diameter.
This beam is 1/2 IN. diameter elements and thus it captures a lot
more signal. It weighs about 9 pounds total and when completed, you
can rotate it with any small TV rotor. You can add elements anytime
and because the BOOM is FENCE POST, you can add any length to the
boom for less than 10 bucks. I recently built a 5 element model for
under $25.00. It rotated well with a TV rotor, but the antenna was
so "sharp" that the TV rotor did not have the resolution for a full
360 degree at one degree per click (HAM IV is a 360 degree rotor).
ELEMENTS:
REFLECTOR - 120 INCHES located at 0.0 on the BOOM.
DRIVEN - 116 INCHES (58 INCHES per side) DIPOLE MATCH located at 46
inches from the REFLECTOR C/C.
DIRECTOR = 110 INCHES located at 89 inches from the REFLECTOR C/C.
BOOM = 90 INCHES LONG (minimum).
The
DIPOLE MATCH is the secret here. The picture here shows the proper
way to mount the DRIVEN element on the boom. This element is totally
isolated from the boom and unlike the GAMMA MATCH, it will be
broader than the GAMMA due to the small tuned curcuit that matches
the 72 OHM feed point to the 50 OHM unbalanced feed line. The AIR
WOUND BALUN is 6 or 7 turns of coax at 6 inches diameter. The feed
is direct to the small insulator made from junk box parts. The BRASS
ROD is part of the tuned circuit and should be built as shown below.
If you keep these dimensions close, you will have a great performer
and one that will last a long time.
More to come...I have to draw the matching network in Photoshop.
|