DB436 / DB437 / DB438 Directional Antennas
406-420 MHz, 425-445 MHz, 450-470 MHz, 470-494 MHz, 488-512 MHz
Assembly and Mounting Instructions
Page 1 of 2 • July 2002 • 095028-000-M
PRODUCT DESCRIPTION
Decibel designed the DB436/DB437/DB438 multi-element yagi antennas
to provide high directivity and high front-to-back ratio. The DB436/DB437/
DB438 have a band width of approximately 30 MHz with a VSWR of less
than 1.5 to 1. They can be stacked and phased together to form the DB436-
2/DB437-2/DB438-2 or the DB436-4/DB437-4/DB438-4 for additional gain.
DB436/DB437/DB438 INSTALLATION PROCEDURE
Refer to Figure 4 while performing this procedure.
1. After removing the antenna from the shipping box, inspect it for physical
damage and to make sure all parts are on hand.
2. Inspect the antenna feed assembly output connector to determine that
it mates with the end of your station transmission line. Do not remove
any connectors or cables from the antenna feed assembly; they are
part of the antenna.
3. Verify that the frequency band to which your antenna has been tuned
matches the frequency on which your radio system operates.
4. Determine the direction of the desired maximum range and the tower
leg on which the antenna is to be mounted. Mount the antenna to the
tower using the V-bolts and straps furnished, making sure that the “UP”
arrow on the feed dipole is properly positioned. Orient the antenna and
tighten the mounting clamps securely to avoid movement after align-
ment.
5. Decibel recommends that the VSWR be measured at the antenna at
this point. Note this measurement carefully and record it for future refer-
ence.
6. After checking the VSWR at the antenna, connect the station transmis-
sion line to the antenna. Make the connection snug but do not apply
heavy force with pliers. To avoid moisture problems, carefully wrap the
connection with Vapor-Wrap (part no. 11317 or 11316), working the com-
pound into all cracks and smoothing it over the outer jackets. Failure to
waterproof the cable will result in improper operation of the antenna.
Properly secure the feeder cable and antenna transmission line to the
tower in the best position to avoid physical damage to the cable.
7. After the antenna and transmission line installation has been completed,
make a careful check to ensure that:
•
All mechanical connections have been securely made.
•
The antenna is mounted on the proper leg of the tower with
sufficient physical clearance.
•
The radiating element is mounted with the “UP” arrow in the
proper position.
•
All connections have been carefully wrapped with Vapor-Wrap to
prevent moisture problems.
DB436-2/DB437-2/DB438-2 INSTALLATION PROCEDURE
The DB436-2/DB437-2/DB438-2 consist of two DB436/DB437/DB438 multi-
element yagi antennas with a phasing transformer for connecting the two
Figure 4 - DB436/DB437/DB438
Figure 3
Mounting Clamp Detail
Figure 2
Side-by-Side Mounting Detail
DB437 Gold Anodized
Antenna
Horizontal
Polarization
Vertical
Polarization
To transmission line
To transmission line
DB436 Antenna
DB438 Gold Anodized
Antenna
Figure 1 - DB Directional Antennas
GENERAL MOUNTING INFORMATION
The DB436/DB437/DB438 antennas come complete with heavy-duty
mounting brackets and stainless steel clamps for mounting on an angled
or round leg, either on the top or side of a tower or wooden pole. The
unique mounting arrangement of the antenna permits either vertical or
horizontal polarization as well as rapid azimuth orientation (see Figure 4).
When mounting the antenna, make sure the elements clear all guy wires
or other metal objects by at least 2 to 3 feet. When mounting a stacked-
phased array (DB436-2/DB437-2/DB438-2 or DB436-4/DB437-4/DB438-
4), make sure the arrays are stacked collinearly and/or are exactly parallel
to each other in the case of side-by-side mounting. Side-by-side arrays
require a DB5009 mounting bracket for the DB436-2/DB437-2/DB438-2
and a DB5018 mounting bracket for the DB436-4/DB437-4/DB438-4.
Continued on page 2
8635 Stemmons Freeway • P. O. Box 569610 • Dallas, Texas 75356-9610
214 / 631-0310 • Fax: 214 / 631-4706 • Web: www.decibelproducts.com
