Impedence Matching:

Impedance Matching is nothing but in a network source to 
load maximum power can be transfered it is called impedance 
matching

Impedance matching is the practice of attempting to make 
the output impedance ZS of a source equal to the input 
impedance ZL of the load to which it is ultimately 
connected, usually in order to maximize the power transfer 
and minimize reflections from the load.

It is voltage standing wave ratio.

It is the ratio of max voltage to the min voltage along the 
transmission line.

It is the ratio of o/p signal to noise ratio to the i/p 
signal to noise ratio.

In telecommunication, noise figure (NF) is a measure of 
degradation of the signal to noise ratio (SNR), caused by 
components in the RF signal chain. The noise figure is the 
ratio of the output noise power of a device to the portion 
thereof attributable to thermal noise in the input 
termination at standard noise temperature T0 (usually 290 
K).

a superhetrodyne receiver is one which has same carrier 
frequency as the transmitter otherwise the original signal 
recovery will not be possible.

+3 dB is 2 times bigger, +10 dB is 10 times bigger.