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A km long microwave link uses two antennas each having 30 dB gain. If the power transmitted by one antenna is 1 W at 3 GHz. Power received by the other antenna is approximately—
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- 98.6 µW
- 76.8 µW
- 63.4 µW
- 55.2 µW
Correct Option: C
As we know from basic equation of transmitter that
 |  | = (GT)dB + (GR)dB – (32.5 + 20 log r + 20 log f) | ||
| PT | dB |
where r in km and f in MHz so we get by putting the values
| | = 30 + 30 – (32.5 + 0 + 60 + 9.542) | ||
| PT | dB |
= 60 - (102.4)
| log | | | = −4.205 | ||
| PT |
∴ PR = PT × 63.27 × 10−6
= 63.27 μW
