panel RF IN/OUT jack (J1) provides the input to HY1 and
the RF SUM (J2) and CPLR IN (J3) jacks provide the
outputs for receiver testing.
The functioning of hybrid attenuator 1A1A1 is described
b. The hybrid coupler input signals for IFF set
in this chapter. The functioning of the balance of the
transmitter testing are applied through the RF SUM (J2)
components of the test facilities set is self-evident.
and CPLR IN (J3) jacks. The hybrid coupler then
combines the sum and difference RF signals into one
resultant RF output to external test equipment at the
a. The hybrid attenuator basically consists of two
front panel RF IN/OUT jack (J1).
subassemblies, hybrid coupler HY1 and variable
c. The coupler is symmetrical, signals applied to
attenuator AT1. The hybrid attenuator can be used as
any input port (e.g., HY1J1) will divide equally between
an entity to couple RF to or from the IFF set and external
the opposite pair of ports (HY1J2 and HY1J3) and the
test equipment, or AT1 can be used alone as a variable
adjacent port (HY1J4) will be isolated. By the same
principle, if equal amplitude quadrature-phased signals
b. When the hybrid attenuator is used to couple
are applied to adjacent ports (e.g., HY1J2 and HY1J3)
RF, external cable AlW3 connects attenuator AT1 to
they will combine at one output port (HY1J1) and cancel
hybrid coupler HY1. This permits up to 25 db attenuation
out the other (HY1J4). Termination AT2 (to HY1J4) is a
of difference channel RF, below the sum channel RF,
50-ohm matched load and is provided to minimize
when performing receiver testing of the IFF set.
reflected signal from port HY1J2.
d The sum channel overall insertion loss of the hybrid
Attenuator AT1 is a two-terminal, nonrepairable, wide-
coupler from the RF SUM jack (J2) to the RF IN/OUT
band variable attenuator with a direct reading dial. The
jack (J1) is the sum of the losses of W1 (approx 3.
dial is calibrated from 0 to 25 db in 1-db steps. The
db), HY1 (3 db) and miscellaneous losses in J2, CP2,
ATTEN IN/RF DIFF jack (J5) and the ATTEN OUT jack
and the coaxial cable terminated by P1 and J1.
(J4), together with the associated coaxial cabling and
e. The difference channel overall insertion loss of
connectors P3 and P2, respectively, make AT1
the hybrid coupler from the CPLR IN jack (J3) to the RF
accessible at the front panels.
IN/OUT jack (J1) is the sum of the losses of W2 (approx
Hybrid Coupler HY1
3.25 db), HY1 (3 db) miscellaneous losses in J3, CP1,
a. Hybrid coupler HY1 is a four-port, 3 db coupler
and the coaxial cable terminated by P1 and J. These
which evenly divides an input signal from external test
losses when added to the losses of W3 and the AT1
equipment into isolated quadrature-phased outputs, for
circuit (para 5-3, with the ATTENUATOR control set at 0)
are equal to or slightly less than the overall insertion loss
of the sum channel.