Most simple and reliable ASU is device
where the controls on the antenna-switching RF relays coming through
a separate multi-wire cable that usual attached to the feeding
coaxial cable.
Another type ASU is device that controls
antenna-switching RF relays through the central core and braid
of the antenna coaxial cable. The ASU required special code/decode
circuits to select the necessary RF-relay. Below there are schematic
for those both types of the roof ASU.
ASU with Separate multi- wire
cable
An ASU that controls antenna-switching
RF relays by a separate multi-wire cable is very reliable and
simple in design. Figure 7
shows sketch of the system with ASU that controls of the antenna-switching
RF relays by a separate multi-wire cable. The ASU includes two
units. Switching unit A1, that sends control voltage to the RF-relays,
is in the shack. Switching unit A2, that is contained the RF relays,
is on the antenna installation site - on the roof. Figure
8 shows schematic of the unit A1. Figure
9 shows schematic of the unit A2.
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How it works: If there is no coming DC voltage to RF
relays (unit A2), then antenna # 1 is switched on. When DC voltage
is coming to unit A2 and RF relay K1 is powered up in this case
antenna # 5 is switched on, in turn RF relay K2 is powered up-
antenna # 4 is switched on, RF relay K3 is powered up - antenna
# 3 is switched on, RF relay K4 is powered up - antenna # 2 is
switched on. The logical schematic allows use only N- 1 relays
to switch on N antennas. In this case four RF relays allow hook
up five separate antennas. Design of unit A1 is shown in Figure
10 (inside- 10A, front 11B).
Design of unit A2 is shown in Figure
11 (inside- 11A,
front 11B).
Unit that placed on the roof should be
protected from atmospheric influence- from direct contact with
rain, wind, and snow. In perfect deal the unit should be hermetically
sealed. It is very good if the unit may be installed in dry place,
for example, in a loft or attic of the house.
ACU with Control to the RF Relays
through Coaxial Cable
ACU with control of the antenna-switching
RF relays through the central core and braid of antenna coaxial
cable should have code circuit in the shack and decode circuit
on the roof. The code/decode circuits work instead of the multi-
wire cable that is present in discussed above wired ASU.
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