Specifications

MDS 05-3438A01, Rev. E MDS 4790/9790 Series I/O Guide 85
Invisible place holder
Figure 40. Front Panel Removal/Replacement
8.4 Operating Frequency Change Considerations
Changing the radio’s operating frequency through a terminal command
or front panel is an easy process. However, there are frequency-sensitive
components within the radio that could effect operation on the new fre-
quency—the receiver front-end helical coils and an internal duplexer, if
one is present. These elements have resonant circuits that prevent the
transmitter from damaging the radio’s receiver and interfering with
other radios operating on nearby channels. The circuits also attenuate
out-of-band signals that could interfere with receiver operation.
Changes in transmit operating frequency of granter than 100 kHz from
the factory settings are likely to require retuning of the duplexer. Like-
wise, changes in receive operating frequency greater than 5 MHz will
require retuning or the duplexer and/or the receiver’s front-end helical
circuits. (See “MDS 4790/970—Front End Helical Coil Alignment” on
Page 87) Retuning of these circuits will provide operation with max-
imum receiver sensitivity and protection from damage to the radio’s
receiver from the transmitter’s powerful RF output.
The feasibility of large changes in frequency depend on the type of
duplexer installed in the radio, or if there is an antenna switch module
present.
A