CUSHCRAFT LFA-2M16EL User manual

CAUTION: Read All Instructions Before Operating Equipment
308 Industrial Park Road
Starkville, MS 39759 USA
Tel: [phone] Fax: [phone]
VERSION 1A
LFA-2M16EL
16 Element Loop Feed Beam
For 2 Meters
INSTRUCTION MANUAL
111
Cushcraft
Amateur Radio Antennas
Cushcraft
Amateur Radio Antennas

GENERAL DESCRIPTION
UNPACKING
Unpack the antenna and separate the parts according to the drawings. This will simplify
the antenna assembly. Parts have been separated when possible to aid in assembly. Make sure you
have the necessary room to assemble the antenna before unpacking. This antenna will be very long
when finished, don’t try to assemble it inside your house and then move it outside. A car garage with
a couple of saw horses or other means of support will make it easy to handle the antenna when putting
it together. Assembly over grass is not recommended. There are lots of small things that can get lost
forever in grass. Some parts may have extras included so don’t worry if you have some left over when
your done.
WARNING
WHEN INSTALLING YOUR SYSTEM, TAKE EXTREME
CARE TO AVOID ANY ACCIDENTAL CONTACT WITH
POWERLINES OR OVERHEAD OBSTRUCTIONS.
FAILURE TO EXERCISE THIS CARE COULD RESULT
IN SERIOUS OR FATAL INJURY
2
The LFA (Loop Fed Array) Low-Noise Yagi is very different from the traditional dipole fed Yagi in many ways
with its primary benefit being unwanted noise rejection. The LFA has a rectangular shaped, full wave loop
driven element that is laid flat on the boom between and in-line with the parasitic elements . Then there is the
way in which the loop functions. The smaller end sections which run parallel to the boom, are engineered to be
180 degrees out-of-phase with each other. This provides the same effect as is seen within ladder-line feeder; each
side cancels the other out and therefore, minimum radiation occurs. In practice this translates to highly
suppressed side lobes and side-on signal rejection. This feature also plays a role in reducing F/B (Front to Back
ratio), F/R (Front to Rear ratio) and broad-banding of the antenna too. It is these attributes which help give the
LFA class-leading all-round performance at almost any boom length and for any given band.

BOOM IDENTIFICATION
Here are the 7 boom sections with measurements displayed for the pre-drilled holes. The numbers on top
are the distance in inches from the rear of the boom when it is correctly assembled. The numbers on bottom
are the distance in inches from one side of the individual tube. These numbers are to verify correct location
and orientation of each tube. Identify each tube by the color band on it. Once you have identified the tubes,
determine which end of the tube will insert into the middle boom section. Mark this side of the tube 3 inches
from the end. This mark will be used to set the insertion depth into the next size tubing. If the tubes are put
together incorrectly, the elements will be out of place and the antenna will not work properly. Use a sharpie
or other marking pen to draw a line on the tube.
THIS MARK IS INDEPENDENT OF THE IDENTIFICATION MARK
285.25 322
1-1/4 x .058 x 72
9.25 46
395.75
360.25
15.25 50.75
1-1/8 x .058 x 72
428.5
1.5
1 x .058 x 16
1-1/4 x .035 x 72
14.5
8
1.5 24.875 41.125 54.375
42
10.625 1-3/8 x .058 x 72
79.625 111
5.875 40.25
1-1/2 x .058 x 72 with
1-3/8 x .058 x 65 insert
143.875 178.25
213.25 249
6.25 42
1-3/8 x .058 x 72
1
2
3
4
5
6
7
Mark 3 inches from end
Mark 3 inches from end
Mark 3 inches from end
BROWN
RED
ORANGE
YELLOW
GREEN
BLUE
VIOLET

BOOM ASSEMBLY
1-1/4 x .035 x 72
1
1-3/8 x .058 x 72
2
1-1/2 x .058 x 72 with
1-3/8 x .058 x 65 insert
3
1-3/8 x .058 x 72
4
1-1/4 x .058 x 72
5
1-1/8 x .058 x 72
6
1 x .058 x 16
7Front of Antenna
Rear of Antenna
Place a #16 hose clamp over the tube before inserting next section

Feed Loop Assembly
To assemble the feed loop onto the boom you will need the following parts.
2 feed loop ends 1 long 7/16 tube
2 short 7/16 tube
1 insulator
8-32 x 1 bolt
8-32 x 2 bolt
8-32 nuts and lock washers
7/16 X 30
7/16 X 14-1/2
Insert each tube 3 inches into the next using the marks you made. Try your best
to align the holes in each tube. Tighten the hose clamps just enough so that the
tubes do not move. Final alignment of the tubes will likely be needed later. Now
would be a good time to support the boom on a couple of saw horses or something
similar.

Mount the insulator on the Boom at the second hole from the rear of the antenna using the 8-32 x 2
inch bolt. Attach the two short 7/16 tubes to the insulator using the 8-32 x 1 inch bolt thru the holes
in the ends of the tubes. Go ahead and tighten the nuts but do not crush the tubes.
Mount the long 7/16 tube to the third hole from the rear of the boom using a longer 8-32 x 2-1/4
bolt, half washer and element saddle.
8-32 x 2-1/4 half washer
element saddle
short tubes with insulator
Long tube with saddle
2 IN BOLT
2-1/4 IN BOLT
8-32 x 2
8-32 nut
#8 lock washer
#8 lock washer
8-32 nut
Element saddle and
half washer.
Rear of Antenna
7/16 X 30
7/16 X 14-1/2
7/16 X 14-1/2

Put one hose clamp over each end of each tube. Insert the loop ends into the 7/16 tubes.
Don’t force them. Keep them straight as they go in. Leave them loose for tunning the
SWR later. The tubes will have enough friction to stay without the hose clamps being
tightened.
INSTAL THE ELEMENTS
The Rod elements are labeled with color bands using the
standard resistor color codes. Starting from the rear of
the antenna, the first rod is R1 and the last rod is R13.
R1 is the reflector and R2 is the first director. A chart is
provided and the element colors are listed for each element.
Install them on the boom in the proper location using the
half washer, saddle and 8-32 x 2 inch bolts nuts and lock
washers. Because of different size boom sections, some
bolts need to be longer to mount the element. These bolt
lengths are listed on the next page.
8-32 x 2
8-32 x 2-1/4
8-32 x 2-1/2
half washer
element saddle
R1
R2
R3 R4 R5 R6 R7 R8 R9 R10 R11
R1 R2 R3 R4
R12 R13 R14 R15
BLACK 0
BROWN 1
RED 2
ORANGE 3
YELLOW 4
GREEN 5
BLUE 6
VILOET 7
GREY 8
WHITE 9
3/16 ELEMENT ROD LENGTHS
AND COLORS
R1 41.5 INCH BROWN (Reflector)
R2 37.9 INCH RED (Director #1)
R3 36 INCH ORANGE
R4 36.5 INCH YELLOW
R5 36.5 INCH GREEN
R6 36 INCH BLUE
R7 35.75 INCH VIOLET
R8 35.5 INCH GREY
R9 35.15 INCH WHITE
R10 34.5 INCH BROWN BLACK
R11 34. INCH BROWN BROWN
R12 33.50 INCH BROWN RED
R13 33.50 INCH BROWN ORANGE
R14 33.50 INCH BROWN YELLOW
R15 33.50 INCH BROWN GREEN

Once you have all the elements on in the correct location, check the alignment of the elements on the
boom sections. Element locations are given on the top of the diagram above. You may use this to verify
correct tube overlap between sections and that the booms are assembled correctly.
Rotate the sections to align the elements if needed and re-tighen the clamps.
Boom to Mast
Select the parts shown and install the mast plate onto the boom. The mast plate should be installed
on to the largest section of the antenna (boom section #3) . You may balance the boom
by installing the plate at the center of gravity of the antenna. You can determine this point
by simply holding the antenna and balancing it in your hand. Make sure the elements are in correct
orientation before tightening the U-bolts. Do not allow the mast plate to come within 1 inch of the
elements on that section.
70
401
119 118
119 118
401
84 85 104
404
326
85 010085
104 010104
118 010118
119 010119
401 010401
404 010404
70 190070
326 290326
010084
84
111
2”
2-1/4”
2-1/2
2”
2” 2” 2-1/4” 2-1/4” 2-1/4”
2-1/2 2-1/4”
2”
2” 2” 2” 2” 2”
Element Bolt Sizes
1.5
24.875
41.125
54.375
79.625
111
143.875
178.25
213.25
249
285.25
322
428.5
395.75
360.25
25-1/4 32-7/8 35 36-1/4 38-1/4 32-3/4

Tuning
Your antenna is now ready for tuning. Remove it from your assembly area and mount it on a temporary
mast at least 8 feet off the ground. Using a SWR analyzer or radio and SWR meter, check for
a dip in swr at or about 144.300 MHZ. You should see a dip in the SWR. If not, Check all connections
and retest. If the dip is too low in frequency, move the loop ends in toward the boom. Move each side the
same and keep them both the same distance from the boom. If the dip is too high in frequency, move the
loop ends out away from the boom. It is not necessary to tighten the clamps each time for tuning. Once
the dip is centered where you want it, tighten the clamps on the tubes. Do not use a wrench or powered
device to tighten the clamps. A nut driver or screwdriver is plenty to do the job.
Move out to shift frequency down
Attach your coax to the feed loop using the remaining 8-32 nuts and lock washers.
Make the distance of the exposed conductors as short as possible. Seal this connection
using a appropriate sealant to prevent water from entering the coax. Wind a choke balun
into the coax using a household cleaner or spray paint can. Put 3 turns around the can and
secure the coax together using cable ties. Attach the balun to the boom with tape and route
the coax along the boom to the mast and go down from there.

5/16 x 1-5/8
Chain link
1/4-20 x 1-5/8
5/16 split washer
5/16 hex nut
1/4 2 hex nt
- 0 u
1/4 2 locw asher- 0 k
Tape one end of the cable to the
chain link with electricians tape.
378216
583 Thb e
371 im l
168695 351244
Tape coax to boom
and mast when mounted
at its final loacation
The antenna is now ready for mounting on your pole or tower. Route the coax along the boom
and mast. Secure it using cable ties or electrical tape. Check the antenna over one last time to
make sure everything is in place and secure. If you haven’t already, place the plastic end caps
over the end of the booms. When installing the boom support, pull the rope tight. It may
stretch over time so you may compensate by adding about an inch of height to the ends of the
antenna over the mast mount. Un-screw the turnbuckles all the way and move the clamp up
and down to adjust the tension at first. Us the turnbuckles to make fine adjustments to the
tension. Don’t forget the thimbles on each end of the rope, they prevent the metal from cutting
through when the antenna moves.
12 element Antenna shown in vertical position
for Illustration only. Boom support clamps are
installed on the 1-1/4 inch end boom sections.
1/4-20 nut
1/4 lock washer
1/4 flat washer
turnbuckle
1/4 flat washer
1/4-20 nut
1/4 lock washer
1/4 flat washer
MAST
Thimble
358731
1-1/4 inch tubing
( last section )
Install the tube clamp at the last joint on each end
of the antenna. This will prevent the clamp from
slipping.
BOOM SUPPORT
Place support clamp about 3 feet above the
boom clamp. Use left over rope to prevent
turnbuckle from rotating after installation
by routing it through the eyelets. Pull the
rope tight and tie it off. You may use cable
ties or other means of securing the
turnbuckle if you wish.
024624
About 3 feet
Your U-bolt
may differ.
Tighten the U-bolt first an
then tighten the nuts holding
the turnbuckle.

PARTS LIST
part # Description Qty
190070 boom to mast 1
010401 u-bolt 2
564792 5/16 split washer 4
555747 5/16 hex nut 4
561177 1/4 lock washer 4
554099 1/4-20 hex nut 10
566344 FLAT WASHER 1/4 10
010404 UBOLT 2
745-3116S #16 hose clamp 6
745-3104S #4 hose clamp 4
455630 1-1/4 caplug 1
765-1000 1" caplug 1
465420 driven insulator 1
010229 8-32 x 1 2
010120 8-32 x 2 10
010232 8-32 X 2-1/2 2
014764 8-32 X 2-1/4 5
190028 Half washer 16
190026 element saddle 16
011941 lock washer #8 22
556990 8-32 hex nut 22
164150 ELEMENT R1 1
163790 ELEMENT R2 1
163600 ELEMENT R3 1
163650 ELEMENT R4 1
163650 ELEMENT R5 1
163600 ELEMENT R6 1
163575 ELEMENT R7 1
163550 ELEMENT R8 1
163515 ELEMENT R9 1
163450 ELEMENT R10 1
163400 ELEMENT R11 1
163550 ELEMENT R12 1
163550 ELEMENT R13 1
163550 ELEMENT R14 1
163550 ELEMENT R15 1
178145 DRIVER ELEMENT A 14-1/2 2
178630 DRIVER ELEMENT B 30 " 1
174022 2MTR LOOP END 2
631570 ROPE 30FT
177301-1 BOOM #1 1
177301-2 BOOM #2 1
177301-3 BOOM #3 1
177301-4 BOOM #4 1
177301-5 BOOM #5 1
177301-6 BOOM #6 1
177301-7 BOOM #7 1
5035200 U-BOLT 1
024624 ROPE CLAMP 4
358731 THIMBLE 4
351243 TURNBUCKLE 2
378216 SS STRIP 2
500098 1/4-20 X 1-1/2 BOLT 2
562961 LOCK WASHER 8
168695 1-1/4 TUBE CLAMP 2
195726 SADDLE BRACKET 1