O P E R A T I N G T I P S; Using The Midstage Pad - Motorola BLE Series Installation And Operation Manual

S ec ti on 6

O p e r a t i n g T i p s

When using the BLE*/* in 750 MHz or 550 MHz systems, you must consider the best method for
handling the reduced bandwidth and channel-loading requirement. The following information
helps you determine the best approach.
For distribution systems designed and installed as 870 MHz systems, but carrying a reduced
channel load, there are no further concerns. You can add or remove channels at your discretion.
If the system operates with ADUs, the pilot channel cannot be disturbed. Reduced channel
loading improves distortion.
For lower-frequency systems, such as 750 MHz or 550 MHz, to maintain amplifier gain it is
optimal to use the amplifier and equalizers that match the system frequency. For example,
750 MHz equalizers used in 550 MHz systems, result in reduced amplifier gain. In the BLE*/*
the SFE, as well as the LDR, are designed and optimized to a specific passband. When possible,
in addition to using the equalizers that correspond to your system frequency, also install the
amplifiers designed for that frequency. For example, in a 750 MHz system, a 750 MHz amplifier
is preferred but not required.
U s i n g t h e M i d s t a g e P a d
There are two pad facilities in the forward amplifier. One is the conventional pad location at the
input to the amplifier (JXP-IN) and the other location is between the pre-amplifier and the
output stage (JXP-MID).
The input pad (JXP-IN) is normally changed to accommodate excessive input levels. When
operating at the same output levels, a BLE*/* with an input pad has the same carrier-to-noise
(c/n) and distortion performance as a BLE*/* without the input pad. Because it only attenuates
excess signal, it has no effect on the overall performance of the BLE*/*.
You can use the midstage pad (JXP-MID) to reduce the gain of the BLE*/* with minimal impact
to the noise figure, thus improving the c/n performance. There is a penalty, however, for using
this technique. When operating at the same output levels, the midstage pad forces the
pre-amplifier to operate at a higher output level. This degrades the station distortion
performance. Depending on: (1) the specific parameter being considered (CTB, CSO, XMD, noise
figure), (2) operating variables such as output level, and (3) the amplifier configuration,
distortion degradation can range from 0.5 dB to 1.5 dB for each dB of attenuation added.
Operating conditions that require the use of the midstage pad are very rare. It is recommended
that you contact Motorola's TRC or your account representative for specific information
regarding use of the midstage pads.
B L E * / * I n s t a l l a t i o n a n d O p e r a t i o n M a n u a l