Intermediate Frequency System
The basic purpose of the Intermediate Frequency system is to convert the R.F. signals received from Front End system into the intermediate frequencies which are suitable for the transmission with minimum loss and minimum noise insertion. The IF system converts the R. F. signals into 70MHz frequency for both channels (CH-1 & CH-2) which is called first IF Conversion (I IF) conversion. I IF conversion is done in the plug in unit (PIU) C41A and C41B respectively. This 70 MHz IF frequency again converted in 130 and 175 MHz bands. Second IF conversion (II IF) is done in C42 and C43 respectively for C41A and C41B PIUs. This signal is further converted into 130MHz and 175MHz by means of C42 and C43 PIU respectively. These PIU's are called as 130MHz converter and 175MHz converter respectively.
The PIU C44 is recognized as the Monitoring PIU as it monitors the whole IF system. The C45 PIU is called as the control PIU and it controls the working of the whole IF system.
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