Bird Technologies Group 61170A Manual De Usuario

Figure 1 shows a simplified block diagram that
illustrates the down/up conversion principle. An
incoming signal at (Freq IN) is amplified and
applied to the first mixer along with a signal from a
local oscillator (Freq LO). A third signal at an inter-
mediate frequency (Freq IF) is produced as a result
of the mixing. The intermediate frequency is given
by the following relationship:

The IF signal from the mixer then passes through
digital filtering with single channel bandwidth
before being amplified and passed on to the sec-
ond mixer. The second mixer also receives the
same local oscillator signal (Freq LO). The result is
a mixing product frequency at the output of mixer
2. The output frequency (Freq OUT) is given by the
following relationship:

Substituting equation (1) for the “Freq IF” term in
equation (2) allows the “Freq LO” terms to be can-
celed yielding:

The implication of equation (3) is that the frequency
stability of the signal that is processed by this type
of signal booster is not affected by the frequency
stability of the signal booster itself. Frequency sta-
bility depends only on the stability of the signal
source producing the signal to be boosted. A shift
in the LO frequency will cause the center of the fil-
ter bandwidth to move with respect to the signal.
For very narrow filter widths, the channel modules
LO may be locked to a high stability 10 MHz refer-
ence.

It is important to report any visible damage to the
carrier immediately. It is the customers responsibil-
ity to file damage claims with the carrier within a
short period of time (1 to 5 days). Care should be
taken when removing the unit from the packing box
to avoid damage to the unit.

The following sub-sections of the manual discuss
general considerations for installing the booster. All
work should be performed by qualified personnel
and in accordance with local codes.

The layout of the signal distribution system will be
the prime factor in determining the mounting loca-
tion of this unit. However, safety and serviceability
are also key considerations. The unit should be
located where it can not be tampered with by the
general public, yet is easily accessible to service
personnel. Also, consider the weight of the unit and
the possibility for  injur y if it should become
detached from its mounting for any reason.

The booster needs to be installed such that there
can be unobstructed air flow around the equip-
ment. Insure that the ventilation fans at the rear of
the module cabinet are unobstructed. The various
subassemblies within the module cabinet will stay
warm during normal operation so in the interest of
equipment longevity, avoid installation locations
that carry hot exhaust air or are continually hot.

The channelized booster system is shipped to the
customer in sections which must be assembled
into the rack before use. The sections which must
be installed in the rack for a standard system
include the module cabinet and filters. High-power
systems may also require the installation of a
hybrid combiner assembly. To install the channel-
ized booster into the rack perform the following
steps.

1) Install the filter assemblies at the bottom of the

rack using the supplied mounting screws. Face
the cable connectors towards the back of the
rack.

2) Install the module cabinet in the rack with the

supplied screws. Place the module cabinet
above the filters. Leave enough room above the
module cabinet to install a second cabinet if
required.

3) For high powered systems install the hybrid

combiner assembly in the rack using the sup-
plied mounting screws. For convenience its
best to place the combiner in the middle of the
rack between the filters and the module cabinet.

4) Interconnect the sections with the supplied

cables. The cable ends are tagged at the fac-
tory before shipment to help you make the cor-
rect interconnections.