ISOTRON 20/15/10
SO SIMPLE AND SO RUGGED!
This article will also appear on our web site.
A REMOTE COAX SWITCH
It is common to have more than one antenna on the mast or tower we use for our station. It is a savings cost to use only one feedline
to all the antennas rather than running a feedline for everyantenna. It also makes the installation less complex.
A remote antenna switch makes this possible. There are commercial units made and will work well. It consists of the switch box at the
antennas and a control box at the station. The commercial units operate the control box through the coax going up to it. However,
some may be interested in building their own.
The schematics below show the Switch box, Control box and Relay connections.
REMOTE SWITCH BOX. This design is for four outputs. It consists of four relays, four output connectors (SO-239) and four common
diodes.
There are three connections to operate four relays (1, 2 and Common). If the common is a negative polarity and 1 positive, it
will turn on Relay 1 only. Reverse polarity and Relay 2 will turn on. Switch from connection 1 to 2 and you can control Relays 3 and
4 in the same manner.
A weather proof box is needed to house the relays. This can be acquired at an electrical supply.
The four outputs can be on the top of the box and the one input on the bottom inside the box. The coax from the station can go through
a hole in the bottom of the box to make the connection.
Mounting the box can be from its side to the mast or tower leg.
CONTROL BOX. Real simple. If you are using 12 volt relays, you will need a 12 volt power supply. This will feed Switch 1 the DPDT
switch. This switch reverses polarity. Switch 2 is a SPDT and selects between connection 1 and 2 on the remote relay box.
RELAYS. My preference is a DPST. I found it to work better if the shield and center conductor are switch out. Most commercial units
switch out only the center conductor. This works fine unless the coax out of the switch box is long. This could affect the tuning
of the other antennas selected.
The DPST relays is connected to each of the four connectors (SO- 239) on one side. The other side is connected to a single input
connector that receives the main feedline.
WIRING. The remote switch box should be wired with at least a #12 solid copper wire. Connections should be short and neat. The heavy
wire will also aid in the mounting of the relays.
The Control box can be wired with #18 hook up wire. The control line from the Control box to the Remote switch can be lite.
Standard telephone wire cable is fine.
It is an easy project and you will find it quite useful.
73,
Ralph WD0EJA
01-19
BILAL COMPANY
137 MANCHESTER DR.
FLORISSANT, CO. 80816 U.S.A
PH/FX: 719/687-0650