How do you choose a local oscillator frequency?

Assuming an intermediate frequency of 60 MHz, the local oscillator will track at a frequency of 60 MHz higher than the incoming signal. For example, suppose the receiver is tuned to pick up a signal on a frequency of 1030 MHz. The local oscillator will be operating at a frequency of 1090 MHz.

What is the purpose of local oscillator?

In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequency of the local oscillator and frequency of the input signal.

What is the function of local oscillator in superheterodyne receiver?

The local oscillator excite a frequency for mixing with the incoming signal to get the intermediate frequency. Most radar receivers use megahertz intermediate frequency (IF) with a value between 30 and 75 megahertz. The IF is produced by mixing a local oscillator signal with the incoming signal.

Why is it that the RF section and the local oscillator are ganged tuned?

There is a fixed difference in frequency between the local oscillator and the RF amplifier at all times. This fixed difference and ganged tuning ensures a constant IF over the frequency range of the receiver.

Why local oscillator frequency is higher than signal frequency?

The reason a higher frequency is commonly chosen in a Super heterodyning receiver, is to leave more distance between the difference or intermediate frequency and the other two frequencies so that the IF signal can be more easily passed through a filter and attenuate the the original two signals.

What is the advantages of Superheterodyning?

The superheterodyne receiver offers superior sensitivity, frequency stability and selectivity. Compared with the tuned radio frequency receiver (TRF) design, superhets offer better stability because a tuneable oscillator is more easily realized than a tuneable amplifier.

Which oscillator is used in local oscillator?

The 6U8A was originally designed for use as a mixer and local oscillator in television and FM receivers, and thus is ideal for this application. The triode is used as the local oscillator, and the pentode is used as the mixer. The two sections are internally shielded from each other.

Why the local oscillator frequency is always kept higher than the signal frequency in super heterodyne receiver?

Why do we use intermediate frequency?

The main reason for using an intermediate frequency is to improve frequency selectivity. In communication circuits, a very common task is to separate out, or extract, signals or components of a signal that are close together in frequency.

What is the advantage of Superheterodyning?

Why is local oscillator frequency kept higher?

As a listener tunes across the broadcast band, the local oscillator is also tuned in synchronism so as to precisely produce a single-frequency signal (essentially an unmodulated carrier signal) which is higher in frequency by 455 kHz in comparison to the incoming signal.

What is a local oscillator?

Its tuning is ganged to that of an LC sine wave oscillator called the local oscillator, but with the two tuned circuits having a frequency difference called the intermediate frequency (IF). (Oscillators are described in detail in Chapter 11 .) In most cases the local oscillator frequency is made higher than that of the required carrier so that

What is the intermediate frequency of an oscillator?

It generally ranges from 88 to 108 MHz (a 20 MHz span) and the Intermediate Frequency (IF) is chosen to be at 10.7 MHz (slightly higher than twice the range of 20 MHz). With an IF of 10.7 MHz the local oscillator (LO) can be 10.7MHz lower (or higher) than the signal to be received.

Does the local oscillator change the frequency of the incoming RF signal?

In reality it is not the local oscillator that changes the frequency of the incoming RF signal. This operation is performed by the mixer. Local oscillators and mixers are used in transmitters and receivers. A superheterodyne receiver is a good example of how local oscillator and mixer are used.

What is the local oscillator frequency of a superhet receiver?

In most cases the local oscillator frequency is made higher than that of the required carrier so that Fig. 9.26. A superhet receiver. where fLO is the local oscillator frequency, fS is the r.f. signal carrier frequency and fIF is the intermediate frequency.