Double spotting is a condition where the same desired signal is detected at two nearby points on the receiver tuning dial . One point is the desired point while the other is called the spurious or image point. ... Poor front-end selectivity and inadequate image frequency rejection leads to double spotting.
What is double spotting in receiver?
(i) Double spotting : Double spotting means the same stations gets picked up at two different nearby points, on the receiver dial . It is due to poor front end selectivity i.e. inadequate image frequency rejection. ... Double spotting can be reduced by increasing the front end selectivity of the receiver.
What is meant by double spotting in am superheterodyne receiver?
“Double-spotting” is a term that means that the wanted station is tuned in at two spots on the dial . These spots would be just 60kHz apart if an IF of 30kHz is used. So how does this occur? In a superhet receiver, the local oscillator frequency is offset from the wanted station by the frequency of the IF amplifier.
What is a double superheterodyne?
Double superheterodyne receivers, which are also variously known as double-conversion receivers or triple-detector receivers, are commonly used in, for example, UHF communications. Such receivers provide high gain without instability, good suppression of image frequencies, and high-adjacent channel selectivity.
What is selectivity and fidelity in a receiver?
Fidelity of a receiver is its ability to reproduce the exact replica of the transmitted signals at the receiver output . For better fidelity, the amplifier must pass high bandwidth signals to amplify the frequencies of the outermost sidebands, while for better selectivity the signal should have narrow bandwidth.
What is the other name of double spotting?
This is known as Double spotting phenomenon. It is also known as Adjacent channel selectivity .
What are the characteristics of a good receiver?
A great receiver is such a complicated combination of traits— agility, body control, strength, quickness, soft hands, physical stamina, concentration, focus, toughness, pride, eye-hand coordination, vision , intelligence, the ability to conceptualize concepts.
What is if of superheterodyne FM receiver?
The RF amplifier amplifies the received signal intercepted by the antenna. The amplified signal is then applied to the mixer stage. The second input of the mixer comes from the local oscillator. The two input frequencies of the mixer generate an IF signal of 10.7 MHz .
How does a superheterodyne receiver work?
The superheterodyne receiver operates by taking the signal on the incoming frequency, mixing it with a variable frequency locally generated signal to convert it down to a frequency where it can pass through a high performance fixed frequency filter before being demodulated to extract the required modulation or signal.
What are the receiver parameters?
The degree of amplification of a radio receiver is measured by a parameter called its sensitivity, which is the minimum signal strength of a station at the antenna, measured in microvolts, necessary to receive the signal clearly, with a certain signal-to-noise ratio.
What are the disadvantages of superheterodyne receiver?
One major disadvantage to the superheterodyne receiver is the problem of image frequency . In heterodyne receivers, an image frequency is an undesired input frequency equal to the station frequency plus (or minus) twice the intermediate frequency.
What is the disadvantage of using a double receiver?
Drawbacks or disadvantages of Superheterodyne Receiver
➨It requires additional LOs (Local Oscillators) and RF Mixers to convert signal from RF to IF before conversion to baseband . This increases cost of overall receiver.
What is superheterodyne principle?
The superheterodyne receiver is the most common configuration for radio communication. Its basic principle of operation is the translation of all received channels to an intermediate frequency (IF) band where the weak input signal is amplified before being applied to a detector .
What is fidelity of a receiver?
The fidelity of a receiver is its ability to accurately reproduce, in its output, the signal that appears at its input . ... Good fidelity requires that the receiver pass a broader band to amplify the outermost frequencies of the sidebands.
What is meant by selectivity and sensitivity?
Sensitivity refers to a radar detector’s ability to pick up police signals at the greatest distance . Selectivity refers to the detector’s ability to filter out signals that are not true police signals, yet operate on the same frequencies as police radar (i.e. security alarms, garage doors, automatic doors, etc.).
How do I increase the sensitivity of my receiver?
- A smaller bandwidth could be used. ...
- The loss in the preselect filter or switch could be reduced. ...
- The noise figure of the LNA could be improved.
- The LNA gain could be increased reducing the effect of the mixer on. ...
- A lower NF in the mixer would also improve the system NF.
