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Page 40
The DB18 Yagi offers high performance regardless of which band or direction the antenna is in. To do this,
at any given time each EHU functions as a driven element. This is accomplished by using a single feed line,
and switching in and out each driven element using a relay. The coax switch housing is where the relays
and the relay board are located.
The installation of the coax switch box is not difficult, but as with all wiring functions, it is critical that you
take great care to ensure that the wiring is correct. Always make sure the electronic controller is completely
disconnected from the control cable and the power is off while doing any wiring.
Locate the coax switch mounting bracket (PN 10-1619-01). Use two 5/16” x 3-1/2” hex head bolt (PN 60-
0065) and two 5/16” Nylock nuts (PN 60-0046) to connect to the boom using two 2” aluminum saddle
halves (PN 10-1601-22) as shown in
figure 4.01
.
Position the base portion of the coax switch box onto the mounting plate. Line up the two holes located on
the inside of the aluminum case with the holes in the mounting plate as shown in
figure 4.02
. Insert two
#10 x 5/8” machine screws (PN 60-01130) through the holes and secure with two #10 Nylock nuts (PN 60-
0019) as shown in
figure 4.03
. A nut drive works well if you have one available. Be sure the coax switch is
level before tightening. Do not forget to use a set screw on the exposed portion of the aluminum saddle.
Figure 4.04
shows the mounted coax switch base.
Locate the 4 conductor control cable, it will be a single piece, 3 ft in length. Trim the cable jacket off (about
1-1/2” will suffice) and remove the foil. Be careful when removing the cable jacket—too much pressure can
cause damage to the other wires. Trim the reinforcing thread so that you end up with a cable end that
looks like
figure 4.05
.
Only three of the four wires are used, along with the shield wire. The green wire needs to be trimmed as
shown in
figure 4.06
. Use electrical tape to cover the end of the trimmed green wire, to ensure that there is
no opportunity for an electrical short to occur.
Figure 4.07
shows the completed control wire prep. It is not
required, but you may want to tin the ends of the control cable, to prevent fraying of the copper strands.
CHAPTER FOUR
SECTION 4.0
COAX SWITCH HOUSING
MOUNTING THE COAX SWITCH HOUSING ASSEMBLY
FIG. 4.06
FIG. 4.05
FIG. 4.07
FIG. 4.01
FIG. 4.03
FIG. 4.02
FIG. 4.04