TM 11-6625-2398-15-3
CHAPTER 5
FUNCTIONING
b. The hybrid coupler input signals for iff set
5-1. General
transmitter testing are applied via the RF SUM (J2) and
CPLR IN (J3) jacks. The hybrid coupler then combines
The functioning of the hybrid attenuator (A1) and cable
the sum and difference rf signals into one resultant rf
W13 is described in this chapter. The functioning of the
output to external test equipment at the front panel RF.
balance of the components of the test facilities set is
IN/OUT jack (J1).
self evident.
c. The coupler is symmetrical, signals applied to any
5-2. Hybrid Attenuator
input port (e.g., HY1J1) will divide equally between the
opposite pair of ports (HY1J2 and HY1J3) and the
adjacent port (HY1J4) will be isolated. By the same
a. The hybrid attenuator basically consists of two
principle, if equal amplitude quadrature-phased signals
subassemblies, hybrid coupler (HY1) and variable
are applied to adjacent ports (e.g., HY1J2 and HY1J3)
attenuator (AT1). The hybrid attenuator can he used as
they will combine at one output port (HY1J1) and cancel
an entity to couple rf to or from the iff set and external
at the other (HY1J4). Termination AT2 (to HY1J4) is a
test equipment, or AT1 can be used alone as a variable
50 ohm matched load and is provided to minimize
attenuator.
reflected signal from port HY1J2.
b. When the hybrid attenuator is used to coupler rf,
d. The sum channel overall insertion loss of the
external cable A1W3 connects attenuator AT1 to hybrid
hybrid coupler from the RF SUM jack (J2) to the RF
coupler HY1. This permits up to 25dB attenuation of
IN/OUT jack (J1) is the sum of the losses of W1
difference channel rf, below the sum channel rf, when
(approximately 3.75dB), HY1 (3dB) and miscellaneous
performing receiver testing of the iff set.
losses in J2, CP2, and the coaxial cable terminated by
P1 and J1.
5-3. Attenuator AT1
e. The difference channel overall insertion loss of
Attenuator AT1 is a two-terminal, non-repairable, wide-
the hybrid coupler from the CPLR IN jack (J3) to the RF
band variable attenuator with a direct reading dial. The
IN/OUT jack (J1) is the sum of the losses of W2
dial is calibrated from 0 to 25dBH in 1-dB steps. The
(approximately 3.25 dB), HY1 (3dB) and miscellaneous
ATTEN IN/RF IFF jack (J5) and the ATTEN OUT jack
losses in J3. CPL, and the coaxial cable terminated by
(J4), together with the associated coaxial cabling and
P1 ;J1. These losses when added to the losses of W3
connectors P3 and P2, respectively, make AT1
and the AT1 circuit (para 5-3, with the ATTENUATOR
accessible at the front panels.
control set at 0) are equal to or slightly less than the
overall insertion loss of the sum channel.
5-4. Hybrid Coupler HY1
5-5. Cable W13
a. Hybrid coupler HY1 is a four-port, 3-dB coupler
which evenly divides an input signal from external test
equipment into isolated quadrature-phased outputs, for
Cable W13 is a nonrepairable, coaxial-type, tuned-stub
receiver testing of the iff set. Front panel RF IN/OUT
line (open circuit at one end). It is used as a strip line
jack (J1) provides the input to HY1 and the RF SUM
coupler termination for con
(J2) and CPLR IN (J3) jacks provide the outputs for
receiver testing.
5-1
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