How it works: RF voltage for antenna and
control voltage for RF relays are going through one coaxial cable.
The RF and Control voltages are separated at input and output of
the coaxial cable with help of RF chokes. Inside the unit A1 installed
main transformer that provides supply voltage for RF-relays. Logical
for the code/decode circuit is very simple. If supply voltage is
not coming to the coaxial cable then antenna # 1 is switched on.
If the voltage in negative polarity (relative to the braid of the
coaxial cable) is going to the coaxial cable then relay K1 powered
up and it is switched on antenna # 3. If the voltage in positive
polarity (relative to the braid of the coaxial cable) is going to
the cable then relay K2 powered up and it is switched on antenna
# 2. If the AC is going to the cable then both relay K1 and K2 powered
up and there is switched on antenna # 4.
The RF relays used in the unit A2 should
all use the same switching on voltage. Relay K2 is DPDT Relay. There
is possible by such relay on e- bay or at some other places (MOUSER,
DIGI-KEY). Anyway the relay may be substituted by common use SPDT
Relay. Inner core of the coaxial cable should withstand both the
antenna RF current and the switching on RF relay current.
Design of the unit A1 is shown in Figure 14 (inside- 14A,
front 14B). Design of the
unit A2 is shown in Figure 15
(inside: 15A - front: 15B).
Unit A2 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.
14 Design of Unit