Interview_Questions

#Interview_Questions
Why we are using -48v in all equipments In BTS of  #GSM Network?

Well there are a number of reasons.

1) Higher voltage means more danger to technicians, lower voltage means less distance.  In rural areas, these voltages are increased using special equipment to deal with long runs.   The 48V is a compromise.

*when we have +ve voltage we cannot transmit for long distance cause that will come to 0 volt or voltage get attenuated but if we have -48 volt that voltage lower to ground potential losses will be very less cause always energy flows from higher potential to lower so so -48 lower potential simply never come to ground potential.

2) 48V is easy to create with 4 - 12V batteries.  So, backup.

3) Negative voltage is used rather than positive because of corrosion.  Positive voltage eats the copper wires if they get wet.

4) Lightening strikes are positive most normally and this allows filtering to ground these while not impacting the signal.

Is there any reasons else!!!!

Que. 2.:- What is VSWR?
Ans:- Standing wave ratio (SWR) is the ratio of the amplitude of a partial standing wave at an antinodes (maximum) to the amplitude at an adjacent node (minimum), in an electrical transmission line. The SWR is usually defined as a voltage ratio called the VSWR, for voltage standing wave ratio.

VSWR=Vmax/Vmin

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