M2 Antenna Systems 2M7X User manual
M2 Antenna Systems, Inc. 4402 N. Selland Ave. Fresno, CA 93722
Tel: (559) 432-8873 Fax: (559) 432-3059 Web: www.m2inc.com
©2021 M2 Antenna Systems Incorporated 3-15-21
Rev.00
Model .........................................2M7X
Frequency Range.......................144 To 148 mHz
*Gain ..........................................12.3 dBi
Front to back ..............................20 dB Typical
Beamwidth ...............................E=43° H=50°
Feed type ...................................“T” Match
Feed Impedance. .......................50 Ohms Unbalanced
Maximum VSWR........................1.2:1 Typical
Input Connector..........................“N” Female
Power Handling ..........................1.5 kW
Boom Length / Dia......................8’ 10” / 1”
Maximum Element Length..........40-1/2”
Turning Radius: ..........................63-1/2”
Stacking Distance.......................6’ 8” High & 7’ 3” Wide
Mast Size....................................1-1/2” to 2” Nom.
Wind area / Survival ...................0.50 Sq. Ft. / 100 MPH
Weight / Ship Wt.........................3 Lbs. / 4 Lbs.
M2 Antenna Systems, Inc.
Model No: 2M7X
FEATURES:
M2 is always trying to design and build new antennas to fit the needs of amateur radio operators. The “X” series
of antennas are all designed to keep the packaging under 48” long to minimize oversize surcharges applied by shippers.
The “X” serries antennas offer the same performance as its predecessor, but with shorter boom sections. The boom sec-
tions also have a thicker wall for added strength. A side benefit of the “X” series antenna are that they are more portable
with the smaller sections. The 2M7X replaces our very popular 2M7.
The 2M7X is a computer optimized Yagi that will outperform longer old design antennas. The 2M7 covers the
whole band with only slight performance degradation at the band edges. Side lobes are very low and it is perfect for
stacking 2 or more. Its light weight and durability make it great for portable hill topping.
The 2M7X is built for long term electrical and mechanical integrity. The CNC machined “T” Match Block features
O-ring sealed connectors and is internally sealed with a space-age silicone gel with nearly 4 times the dielectric strength
of air. Elements are 6061-T6 3/16” aluminum rod, mounted through the boom on UV stabilized button insulators. All hard-
ware is stainless steel except U-bolts. Other key electrical and mechanical parts are CNC machined for accuracy and du-
rability.
SPECIFICATIONS:
*Subtract 2.14 from dBi for dBd
Tools handy for assembly process: screwdriver, 11/32” spin-tite or socket, 7/16” and 1/2” end wrenches
and/or sockets, measuring tape.
1. Assemble the boom sections using the 8-32 X 1-1/4 screws and locknuts.
2. Lay out the elements by length and position as shown the DIMENSION sheet. Start with the
REFLECTOR (longest) element. Balance on finger to find rough center and push on a black button
insulator to about 1/2” from center. Install the element through the holes at the boom and push on the
second button, snugging it up into boom. DO NOT BOTHER WITH ACCURATELY CENTERING the
element at this time and DO NOT INSTALL the stainless steel SHAFT RETAINERS yet. This is easier
to do after all the elements are installed in the boom.
3. Install the 3/16” rod DRIVEN ELEMENT as you did the reflector. Then continue with the installation of
the DIRECTORS.
4. Now begin centering the elements. Use a tape measure to EQUALIZE the the element length on
each side of the boom. Once you have all the elements centered, sight down the element tips from
the rear comparing each side. Look for any obvious discrepancies and correct if found.
5. Begin installing the stainless SHAFT RETAINER to one side of the element. Use thumb and index
finger to hold a retainer over end of the 3/8 x 3” push tube (chamfer inner edge of tube) (retainer
dished into tube). Hold the element firmly and start the retainer onto the rod by applying pressure with
the push tube. Push the retainer until up tight against the button insulator (Locking pliers, lightly
clamped up against opposite button insulator will help maintain center reference and keep you from
pushing the first retainer too far). It is a good idea to install the second SHAFT RETAINER after final
testing.
6. Mount the DRIVEN ELEMENTASSEMBLY to the underside of the boom using a single 8-32 X 1-1/4"
screw. Orient the block with feed connector facing forward and balun connectors facing to rear. Block
orientation may be reversed if you wish feedline to exit rear of boom.
7. Attach balun to the DRIVEN ELEMENT ASSEMBLY and tighten the connectors gently using a 7/16"
end wrench. Coil balun once, if necessary, so balun does not extend beyond end of boom. Form the
balun close to the boom and secure with a nylon cable tie, snug but not crushing or kinking the coax.
2M7X ASSEMBLY MANUAL
2M7X DIMENSION SHEET
8. Install the 8-32 x 1/4” set screws (internal Allen head - tool supplied) into the SHORTING BARS.
Slide the bars onto the 3/16” rod driven element tips and then onto the Driven Element Block
Rods. Position the Shorting Bars as specified on the Dimension Sheet: 2-9/16” from the outer face
of the block to the inner face of the bar. Align the bars and rods with each other and tighten the set
screws.
9. The boom to mast plate is normally mounted at the balance point. Since the feedline represents
significant weight it is best to have it attached and fastened along the boom with cable ties before
final mounting of the plate. Use two 1" U-bolts and the stainless nuts and lock washers provided
(no cradles are used). DO NOT OVER TIGHTEN. 2” U-bolts are provided for mounting the
antenna to your mast. Never mount to a metallic mast or cross boom in the same plane as the
elements. Pattern and performance will deteriorate. See next step.
10. INSTALLATION AND TESTING STACKING INFORMATION
A. To protect your investment in this high performance antenna, always use high quality coax and
connectors. Old, corroded, or poor quality materials are common sources of serious performance
losses.
B. Test the antenna, connectors and feedline, BEFORE installing to your mast or tower. At 6 feet
or more the antenna will exhibit VSWR similar to higher mounting heights. Set antenna on a
ladder or temporary mast. Check for continuity and match across the band. It should be close to
“spec” across the rated bandwidth. When satisfied, add the second SHAFT RETAINERS as
described in step 5.
C. STACKING REMINDERS:
1. All driven element blocks MUST be oriented to the same side of boom.
2. All boom-to-mast plates MUST be mounted at the same point on the boom.
3. Feed / phasing lines MUST be of equal electrical length or multiples of 1/2 wavelength in order
to maintain equal phasing in the array. Improper phasing can severely deteriorate performance.
4. As a general rule, you never want to have metallic structures, such as a mast or feed lines
parallel to the elements unless it is behind the reflector. Having metallic structure in the same
plane as the elements in front of the reflector element can cause VSWR problems and or skewed
patterns.
FOR HORIZONTAL POLARIZATION, the antenna may be mounted to a METALLIC vertical mast
or a horizontal NON-METALLIC cross boom. If mounted to a horizontal cross boom, route the
feedline forward to the boom-to-mast plate, loop down, and bring back to cross boom at least 6”
beyond element tips. Antennas are typically stacked one above the other in horizontal polarity.
SEE SPEC SHEET FOR STACKING DISTANCE. See Stacking Reminders.
FOR VERTICAL POLARIZATION, the antenna may be mounted to a NON METALLIC
VERTICAL MAST or a horizontal METALLIC cross boom. If mounted to a NON METALLIC
vertical mast, Turn the driven element 180 degrees so the feed line and “N” connector is facing to
the rear of the antenna, route the feed line to the rear of the antenna keeping 4” to 6” behind the
reflector element. Let the cable droop at least 6 inches BELOW THE VERTICAL ELEMENT TIPS.
Re-attach the feed line to the mast below the element tips. A simple structure can easily be
fabricated if you want something to support the feed line. See M2 “L” brace kit for ideas. Vertically
polarized Antennas are typically stacked side by side on a horizontal cross boom. See Stacking
Reminders.
If you are unsure about stacking multiple antennas, please call M2 and let us help you DO IT
RIGHT! Visit our website, https://www.m2inc.com/blog/ for other tips.
2M7X ASSEMBLY MANUAL
DESCRIPTION QTY
BOOM SECTION, 1 X .065 X 37-1/8” SOE (M2ABS2M7X-1).................1
BOOM SECTION, 1 X .065 X 37-1/8” SOE (M2ABS2M7X-2).................1
BOOM SECTION, 1 X .065 X 35-3/4” STR (M2ABS2M7X-3) .................1
ELEMENTS, 3/16 ROD X DIMENSION SHEET .....................................1
DRIVEN ELEMENT ASSEMBLY (SADEA2MVHF1)...............................1
BALUN, RG-6 1/2 WAVE (SABAL2M144) ..............................................1
BOOM-TO-MAST PLATE, .125 X 3” X 4” (M2APT0019) ........................1
U-BOLT 1”...............................................................................................2
U-BOLT AND CRADLE, 2”......................................................................2
ASSEMBLY MANUAL.............................................................................1
IN HARDWARE BAG:
SHORTING BAR, (M2ASB0090) ............................................................2
BUTTON INSULATORS..........................................................................14
KEEPER, 3/16” SS..................................................................................14
NUT, 5/16-18 HEX SS ............................................................................4
LOCKWASHER, 5/16 SS........................................................................4
NUT, 1/4-20 HEX SS ..............................................................................4
LOCKWASHER, 1/4 SS..........................................................................4
SETSCREW, 8-32 X 1/4 SS....................................................................4
SCREW, 8-32 X 1-1/4 SS .......................................................................5
LOCKNUT, 8-32 SS ................................................................................4
CABLE TIE, 7” NYLON ...........................................................................3
ALLEN HEAD WRENCH, 5/64”...............................................................1
PUSH TUBE, 3/8” X 3”............................................................................1
Carefully manufactured by:
M2 ANTENNA SYSTEMS, INC.
4402 N. Selland Ave.
Fresno, CA 93722
(559) 432-8873 Fax: 432-3059
www.m2inc.com Email: sales@m2inc.com
2M7X PARTS & HARDWARE
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