Cushcraft DB-46M8EL User guide

Cushcraft

Amateur Radio Antennas

DB-46M8EL

Dual band 6 and 4 Meter, 8 Element

Beam Antenna

INSTRUCTION MANUAL

VERSION 1B

CAUTION: Read All Instructions Before Operating Equipment

Cushcraft

Amateur Radio Antennas

308 Industrial Park Road

Starkville, MS 39759 USA

Tel: [phone] Fax: [phone]

GENERAL DESCRIPTION

The DB-46M8EL is a dual band 50, 70 Mhz 8 element beam antenna . It uses a single feed point
for both bands eliminating the need for a splitter or duplexer. the open sleeve method of providing dual
band performance is very efficient. there are no traps or coils inducing unwanted loss and there are no
compromise spacing of elements with this antenna either. Each band has a set of full-length elements
which have had both length and position on the boom computer optimized using the latest in Partical
Swarm Optimisation techniques (PSO) ensuring the best possible performance. This antenna provides
both a 4 element Yagi on 50 Mhz and a 4 element Yagi on 70 Mhz although only the 50 Mhz element
is fed. All of the 70Mhz elements are parasitic.

UNPACKING

Unpack the antenna and check the parts against the Parts List and 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 large
when finished. Try to assemble it in a large open area clear of obstructions and people. A driveway and
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. The design of the antenna makes it very easy to assemble.

Tools you will need

Tape measure in inches. A tape measure in feet and inches will do but you will have to convert.
7/16 wrench and/or nut driver
½ inch wrench
Phillips screwdriver
Flat head screwdriver for hose clamps

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

Assembly of the Boom

Assembly Instructions

Select the boom-to-mast clamp, (385142-1)
the boom-to-mast bracket (385144-1) and
four (4) 1/4" - 20 x 3/4" bolts (505266)
four (4) internal lockwashers (562961)
and four (4) 1/4" hex nuts (554099)

555747
564792

562961
554099

Place the boom-to-mast bracket (385144-1)
on the boom-to-mast clamp (385142-1)
align the holes and place the bolts in the
four (4) outer holes as shown in Figure 1

Select the two sections of boom (Front and
Rear), and insert them into the boom-to-mast
bracket until they meet at the center. Tighten
the bolts.

Install the U-bolts using the 5/16 nuts (555747)

and the 5/16 split washers (564792).

You may place the boom on a temporary mast or support it from each end.
This will make assembly and measurements easier. Find a location that is
suitable for an antenna this large. A concrete driveway is a good place to
assemble antennas. Any hardware you drop in grass may be gone forever.
Some of the smaller hardware has extra pieces just in case they are dropped.

385144-1

540067

385142-1

Short tube ( 34 inch )

Long tube ( 56 inch )

Front of antenna

3

Assemble the brackets as shown in Figure 2 and
locate them on the boom assembly as shown in
Figure 3. It is easier to assemble the brackets on
the boom at the correct location, rather than try
to slide them on the boom. If you are going to
leave this assembly unattended for more than 15
minutes, we suggest that you tighten the eight
(8) bolts on each bracket, so that they do not
vibrate off. Do not tighten the anchor bolts on the
elements until the elements are completely

installed and aligned. Mark the bracket location on
the boom with a marker at the edge of the bracket
instead of the center. This will ensure the mark is
still visible when the bracket in is the correct spot.
Start from the rear of the boom and work forward.
The measurements are given in total inches from
the rear of the boom. If you need the distance from
each element to the next you may subtract the bracket
measurements to obtain this value. Total distance
is given for better accuracy in element placement.
Distance between elements measurements will cause
cumulative errors as each element is placed. Notice
there are two different locking bolts for the brackets.
The driven element bracket (#1) uses a larger 1/4-20
bolt and square nut.

2 inches

12-1/2 inches

36-1/4 inches

39-1/2 inches

#1 Bracket

44-3/4 inches

461057
Insulator

47-1/2 inches

#11 [10-24 x ½]
#1 [1/4-20 x 3/8]

#11 or #1 Bracket

#1 [ 1/4-20 ]
#11 [ 10-24 ]
Square

1/4-20 x 3/8

1/4-20 x 3/4

1/4

1/4-20

Figure 2

Slide the tube all the way into the bracket
until it just makes contact with the boom.
On the #1 bracket, insert it all the way into
the insulator.

5/8 Insulator on
#1 bracket only

190002 installed
on all brackets
5/8 x 7-1/2 tube

4

80 inches

Front of antenna

84-1/2 inches

Install boom caps

Figure 3