M2 Antenna Systems 6.9-4CDD-125 User manual

M2 Antenna Systems, Inc. 4402 N. Selland Ave. Fresno, CA 93722
Tel: [phone] Fax: [phone] Web: www.m2inc.com
©2018 M2 Antenna Systems Incorporated
9/28/20
REV 1
M2 Antenna Systems, Inc.
Model No: 6.9-4CDD-125
SPECIFICATIONS:
*Subtract 2.14 from dBi for dBd / FS = Free Space
Model .........................................6.9-4CDD-125
Frequency Range.......................6.8 –6.980 MHz cont.
Typical gain ................................12.3 @ 100’ dBi typical
Front to back ratio ......................21 dB typical
Beamwidth ...............................75°
Feed type / Balun .......................SO-239,1:4 Balun
Feed Impedance. .......................200 Ohms
VSWR.........................................1.2:1 typical, 2.0:1 max
Connector ...................................SO-239, Other avl.
Power Handling ..........................3 Kw, Higher avl.
Boom Length / Dia......................42’ / 3” X .125
Maximum Element Length..........49’
Turning Radius: ..........................34’
Mast Size....................................2” or 3” Nom.
Wind area / Survival ...................13.0 Sq. Ft. / 100 MPH
Weight / Ship Wt.........................450 Lbs. / 500 Lbs.
FEATURES:
Recently, M2 engineers developed a new way to make coils using CNC tooling. The result is a precision inductor
increasing Q and lowering loss to new levels. A coil loaded Yagi design was computer optimized, and not one single
change was required on the finished Yagi. This design gets the bandwidth and maintains performance across the band
like no other Yagi. Gain, Front to Back and VSWR are maintained nearly flat across the 6.8 to 6.980 MHz band section.
Mechanically it is easy to assemble. Only the tips of each element are different as all the coils are the same for each
element. The coils themselves float in air minimizing dielectric loss. They are fully covered with a polyethylene cover. This
antenna has been designed to meet your needs and give you years of reliability.

6.9-4CDD-125 ANTENNA OVERVIEW
BEFORE YOU BEGIN: Look over all the DRAWINGS to get familiar with the various parts and assem-
blies in the system. Tools handy for assembly process: screwdriver, 11/32”, 7/16”, 1/2”, 9/16” and 5/8”
spin-tites, end wrenches and/or sockets, and a measuring tape.
Note:
All installations are unique in some way, which means it's OK to preassemble certain hardware, or
rearrange the assembly process to meet specific site requirements. A quick review of the assembly
drawings should help firm up the appropriate strategy. Please remember to double-check all hard-
ware for tightness BEFORE it becomes inaccessible.
One container of zinc paste (Penetrox, Noalox, or equiv.) has been provided to enhance and
maintain the quality of all mechanical and electrical junctions on this system. Apply a thin coat
wherever two pieces of aluminum come in contact or any other electrical connections are made.
It is also useful on screws and bolt threads as an ANTI SEIZE compound.
REFLECTOR
REAR DRIVEN
ELEMENT
FRONT DRIVEN
ELEMENT
DIRECTOR

6.9 COIL OVERVIEW
COIL
(M2ACA1550)
COIL SUPPORT
(M2ACA1554)
COIL INSULATOR
(M2AFG0050)
COIL POST
(M2ACA1575)
(QTY 2)
COIL END CAP
(M2ACA1576)
(QTY 2)
NOTE: COVER REMOVED FOR ILLUSTRATION PURPOSES.
BOOM ELEMENT TIP

6.9 COIL ASSEMBLY
INSTRUCTIONS
STEP 1:
The coil comes wound tight with 16 total turns from the factory. The excess
material will be trimmed off after the coil is in its final position. Using a permanent
marker, draw a straight line from one end of the coil to the other. This will help later
to determine if your coil has grown in diameter during assembly. After final position-
ing of the coil no more 3/4 of an inch of line tilt is allowed. A larger coil will cause the
inductance to change which can cause your antenna to be off frequency.
STEP 2:
The COIL is wound tight at the factory to prevent damage during shipping. Use the
COIL SPREADING TOOL provided, and carefully insert it into the first turn of the
COIL. Now gently push or roll the tool through all 16 turns of the COIL. Now the
COIL is nearly in its final shape and is ready to be threaded onto the COIL SUP-
PORT. Note the reference line drawn earlier, it will have a slight tilt after spreading.
STEP 3:
On one end, use pliers to gently straighten the last 1/2” of the COIL and file
off any burrs.
STEP 4:
Begin threading the COIL onto one end of the COIL SUPPORT. BE CAREFUL to not deform the COIL during this
process. The COIL should thread smoothly. Continue until about 5-1/2 turns are past the COIL SUPPORT or close to the
center. Exact centering is not important. Again, note your reference line.
NOTE: PENETROX PASTE FOR LUBRICATING SCREW THREADS AND TUBING JOINTS HAS BEEN SUPPLIED. USE A VERY SMALL AMOUNT ON
EACH SCREW THREAD AND UNDER THE COIL POSTS DURING THE NEXT OPERATION.
STEP 5:
Insert the COIL INSULATOR (M2AFG0050) into your COIL SUPPORT (M2ACA1554). Rotate the COIL and the
COIL SUPPORT so the leading end of the COIL goes over and just past the inner hole in the COIL INSULATOR. Now slide
on one COIL POST on to one end of the COIL so it is right over the first hole. Next, carefully slide on the ELEMENT SEC-
TION #6 (M2AEP40MC-6) and align it so both holes in the tube match the two holes in the COIL INSULATOR.
STEP 6:
Insert hardware through the ELEMENT SECTION #6 and the COIL INSULATOR and begin threading it into the
COIL POST. Tighten hardware. Thread the SET SCREW into the top of the COIL POST and with about 1/2” of wire protrud-
ing past the COIL POST, tighten the SET SCREW gently. Use supplied ALLEN WRENCH to tighten the SET SCREW.
STEP 7:
The second COIL POST is mounted on the OPPOSITE SIDE of the COIL INSULATOR so 15 1/2 turns of the COIL
are used. The extra 1/2 turn COIL should pass over the COIL INSULATOR hole. Slide on the second COIL POST and align
1/2” TO 3/4”
TILT

6.9 COIL ASSEMBLY
INSTRUCTIONS
it over the hole. Slide on ELEMENT SECTION #4
(M2AEP40MC-4) and fasten the COIL POST to the tubing
assembling using the supplied hardware. Use you refer-
ence line and adjust the coil so the line has no more tilt
than 3/4”
STEP 8:
Insert the SET SCREW into the COIL POST and
tighten gently. Adjust the COIL and COIL SUPPORT loca-
tion for equally spaced turns. The distance between each
turn should be the same as the COIL wire diameter. Once
the COIL is straight and aligned, tighten the final SET
SCREW securely.
STEP 9:
Slide COIL COVER and COIL END CAPS onto
COIL ASSEMBLY. Secure COIL END CAPS into position
by securing hardware through TUBE ASSEMBLIES on
both ends of the COIL ASSEMBLY. Slide ELEMENT
OVERHEAD SUPPORT onto ELEMENT SECTION until it
reaches the head of the screw holding on the COIL COV-
ER. Clamp ELEMENT OVERHEAD SUPPORT in place with screw and locknut.
STEP 10:
Assemble all the remaining COIL ASSEMBLIES by repeating steps 1-9. Set COIL ASSEMBLIES aside for future use.
COIL (15.5 TURNS)
(M2ACA1550)
COIL INSULATOR
(M2AFG0050)
COIL SUPPORT
(M2ACA1554)
ELEMENT SEC-
TION #4
ELEMENT SECTION #6
(M2AEP40MC-6))
COIL POST
(M2ACA1551)
SCREW, 8-32 X 1-1/4”
SET SCREW, 1/4-20 X 1/4”

STEP 11:
At this point it will be helpful to perform the remaining assembly steps with the BOOM ASSEMBLY
elevated off the ground (about 3 feet). This can be accomplished by using sawhorses or something similar.
Wipe off the ends of each BOOM SECTION and apply a small amount of PENTROX. Refer to the drawing be-
low and assemble BOOM SECTIONS as shown. Insert hardware and tighten.
STEP 12:
Add the guy clamps to boom sections 1 # 3, see dimension sheet for location.
6.9-4CDD-125 BOOM ASSEMBLY
INSTRUCTIONS
3” SCHED 40 PIPE X 20’
BOOM SECTION #2
(QTY 1)
GUY CLAMP
(2) BOLT, 3/8-24 X 1.5 SS
(2) LOCK WASHER SS
3.0 X .125 X 145”
BOOM SECTION #1 & 2
(QTY 1)
(2) BOLT, 3/8-16 X 4.0 SS
(2) 3/8-16 NUTS SS
(2) LOCK WASHER SS
THE BOOM SECTIONS ARE LINE
DRILLED AT THE FACTORY. EACH END
WILL HAVE MARKINGS AT THE JOINTS
INDICATING ORIENTATION.

STEP 13:
Assemble the ELEMENT MOUNT
assemblies for the reflector and front director
element. Refer to the assembly drawing to aid in
assembly. Be sure to center the ELEMENT
CENTER SPLICE and the holes are in the
vertical position.
STEP 14:
Assemble the DRIVEN ELEMENT
MOUNT assembly for the DRIVEN ELEMENTS.
Refer to the assembly drawing to aid in assembly.
Be sure to center the INSULATOR and that the
holes are in the vertical position. The DISC
INSULATORS are a press fit. Heating them with
a heat gun or hot water will help in assembly.
6.9-4CDD-125 ELEMENT MOUNT ASSEMBLY
INSTRUCTIONS
BOLT, 1/4-20 X 2-3/4”
LOCKNUT, 1/4-20
(QTY 4)
ELEMENT MOUNTING
PLATE
(M2AEC0040)
(QTY 2)
ELEMENT CENTER SPLICE
(M2ASR0050)
ELEMENT MOUNT ASSEMBLY
REFECTOR OR DIRECTOR
BOLT, 1/4-20 X 2-1/2”
LOCKNUT, 1/4-20
(QTY 4)
CRADLE 3”
(M2AMC0136)
(QTY 2)
VERTICAL RISER
ASSEMBLY
(M2AVR0010)
BOLT, 1/4-20 X 3-1/2”
AND LOCKNUT
(QTY 2)
CRADLE 3-1/2”
(M2AMC0175)
(QTY 2)
ELEMENT MOUNTING
PLATE
(M2AEC0059)
(QTY 2)
BOLT, 1/4-20 X 2-1/2”
LOCKNUT, 1/4-20
(QTY 4)
INSULATOR
(M2AFG0034)
VERTICAL RISER
ASSEMBLY
(M2AVR0010)
BALUN BRACKET
(M2APT0016)
DISC INSULATOR
(M2ADI0020)
(QTY 2)
ELEMENT MOUNT ASSEMBLY
DRIVEN ELEMENT
BOLT, 1/4-20 X 3-1/2”
LOCKNUT, 1/4-20
(QTY 4)
BOLT, 1/4-20 X 3-1/2”
AND LOCKNUT
(QTY 2)

6.9-4CDD-125 ELEMENT ASSEMBLY DETAIL
2 (QTY) SCREW,
8-32 X 1-1/2”
& LOCK NUT
1 1/4 X .058 X 85.5”
1 3/8 X .058 X 56”
1 1/2 X .058 X 60”
1 3/8 X .058 X 53”
1 1/2 X .058 X 60”
1 5/8 X .058 X 56” 1 1/4 X .058 X 60”
1 1/4 X .058 X 24”
1 1/8 X .058 X 24”
1 X .058 X 24”
1 1/8 X .058 X 24”
1 X .058 X 26”
1 X .058 X 27”
3/4 X .049 X 27”
2 (QTY) SCREW,
8-32 X 1-1/4”
& LOCK NUT
IN SOME CASES THE COILS MAY BE PRE ASSEMBLED. IF YOUR COILS ARE PRE-
ASSEMBLED, SKIP THE COIL ASSEMBLY STEPS.
3 (QTY) SCREW
8-32 X 2”
& LOCK NUT
2 (QTY) SCREW,
8-32 X 1-3/4”
& LOCK NUT

NOTE: For the final assembly on all the elements, it is best to perform the next steps on the ground or long flat surface.
This will aid during final adjustment of the ELEMENT OVER HEAD SUPPORT. The ELEMENT HALVES are symmetrical
on both sides EXCEPT FOR THE ELEMENT TIP.
STEP 15:
Use the ELEMENT ASSEMBLY DETAIL to assemble each element half. Add the element halves to the to the pre-
assembled element mount assemblies.
.
STEP 16:
To adjust the ELEMENT TIP, a COMPRESSION CLAMP is supplied for use during tune up. First thread on the
hex nut to capture the screw in the CLAMP. Then slide the COMPRESSION CLAMP so that the screw is lined up with the
hole in ELEMENT SECTION #5. Use the DIMENSION SHEET and set the proper exposed length of the 1/2” ELEMENT
TIP for the appropriate element, then mark the element assembly to avoid confusion later. See GENERIC COMPRES-
SION CLAMP DETAIL page for more detail.
STEP 17:
Tensioning the element overhead guys: Start at the VERTICAL RISER and bend the thimbles open and insert
them into the holes on the top plate of the VERTICAL RISER, then bend them back to there original shape. Cut the HPTG-
1200 in half and Loop the Philystran cord thru the thimble, add qty (2) 1/8 wire clip and leave 3” of excess Philyistran past
the wire clip and tighten, finalize by taping the short tail of Philystran cord down to the main portion of Philystran. Thread
the opposite end of the cord through the ELEMENT OVERHEAD SUPPORT (M2APL0211) (See the LOCK BLOCK DE-
TAIL page) and tension the rope so the element is in a level or neutral position. It is always best to have the element in a
level or neutral position or with a slight sag downward. Over tensioning can lead to a upward bowed element causing in-
stability. This finalizes the element construction.
ELEMENT FINAL
ASSEMBLY INSTRUCTIONS
GROUND OR FLAT SURFACE
ADD THE
APPROPRIATE
ELEMENT TIP
SEE DIMENSION
SHEET
(1) 3/16 THIMBLE
(2) 1/8 WIRE CLIPS

6.9-4CDD-125 ASSEMBLY DETAIL
BOLT, 1/4-20 X 3-1/2”
LOCKNUT, 1/4-20
(QTY 2)
BOLT, 1/4-20 X 3-12”
AND LOCKNUT
(QTY 2)
CRADLE 3.5”
(M2AMC0175)
(QTY 2)
BOLT, 1/4-20 X 2”
LOCKNUT, 1/4-20
(QTY 4)
PHASE LINE CLAMP
BLOCK
(M2APL0035)
(QTY )
USE 3/16 THIMBLE
& 1/8 WIRE CLIPS
VERTICAL RISER
ASSEMBLY
(M2AVR0010)
ELEMENT MOUNTING PLATE
(M2AEC0059)
(QTY 2)
ELEMENT ASSEMBLY
FRONT DRIVEN ELEMENT
VERTICAL RISER
ASSEMBLY
(M2AVR0010)
BOLT, 1/4-20 X 2-1/2”
LOCKNUT, 1/4-20
(QTY 4)
ELEMENT MOUNTING PLATE
(M2AEC0040)
(QTY 2)
BOLT, 1/4-20 X 2-3/4”
AND LOCKNUT
(QTY 2)
CRADLE 3.5”
(M2AMC0136)
(QTY 2)
BOLT, 1/4-20 X 2”
AND LOCKNUT
(QTY 2)
USE 3/16 THIMBLE
& 1/8 WIRE CLIPS
ELEMENT ASSEMBLY
REFLECTOR OR DIRECTOR
ELEMENT
BOLT, 1/4-20 X 3-1/2”
LOCKNUT, 1/4-20
(QTY 2)
BALUN CONNECTS
TO BOTH
PHASE LINE CLAMP
BLOCKS
ON THE FRONT
DRIVEN ELEMENT