Site Logo Home
 
rOm
Quest
Glossary
 
Random
Page
Search
Site
Lush
Sim
Class
Subject
Images
 
Help
FAQ
Sign
Up
Log
In
A Level     Radio     Digital     Simple Receiver        Extras Non Exam     Radio     Simple TRF     >Superhet<    

Radio Superhet


Site for Eduqas/WJEC - Go to the AQA site.

  Extras Non Exam    Radio  0 of 66    Question 1345    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set1 of 66    Question 1346    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set2 of 66    Question 1347    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set3 of 66    Question 1348    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set4 of 66    Question 1349    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set5 of 66    Question 1350    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set6 of 66    Question 1351    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set7 of 66    Question 1352    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set8 of 66    Question 1353    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set9 of 66    Question 1354    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set10 of 66    Question 1355    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set11 of 66    Question 1356    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set12 of 66    Question 1357    Basic Receiver 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set13 of 66    Question 1061    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set14 of 66    Question 1062    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set15 of 66    Question 1063    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set16 of 66    Question 1087    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set17 of 66    Question 1343    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set18 of 66    Question 1088    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set19 of 66    Question 1089    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set20 of 66    Question 977    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set21 of 66    Question 979    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set22 of 66    Question 980    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set23 of 66    Question 981    DAB 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set24 of 66    Question 1090    FM Band 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set25 of 66    Question 1091    FM Band 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set26 of 66    Question 1092    FM Band 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set27 of 66    Question 1286    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set28 of 66    Question 1360    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set29 of 66    Question 1362    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set30 of 66    Question 1363    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set31 of 66    Question 1364    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set32 of 66    Question 1365    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set33 of 66    Question 1258    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set34 of 66    Question 1261    Radio Systems 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set35 of 66    Question 67    Radio Terminology 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set36 of 66    Question 68    Radio Terminology 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set37 of 66    Question 69    Radio Terminology 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set38 of 66    Question 70    Radio Terminology 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set39 of 66    Question 71    Receiver Terminology 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set40 of 66    Question 72    Receiver Terminology 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set41 of 66    Question 314    Sub-systems Radio Modules 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set42 of 66    Question 316    Sub-systems Radio Modules 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set43 of 66    Question 317    Sub-systems Radio Modules 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set44 of 66    Question 1064    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set45 of 66    Question 1358    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set46 of 66    Question 1359    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set47 of 66    Question 915    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set48 of 66    Question 495    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set49 of 66    Question 496    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set50 of 66    Question 497    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set51 of 66    Question 498    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set52 of 66    Question 499    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set53 of 66    Question 500    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set54 of 66    Question 501    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set55 of 66    Question 502    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set56 of 66    Question 503    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set57 of 66    Question 504    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set58 of 66    Question 505    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set59 of 66    Question 506    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set60 of 66    Question 507    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set61 of 66    Question 508    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set62 of 66    Question 509    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set63 of 66    Question 510    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set64 of 66    Question 511    Superhet 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set65 of 66    Question 103    Tuned Circuit Cores 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set66 of 66    Question 54    VHF Radio - Modulation Type 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set  Questions 0 to 66   -->  View All  

Terminology

The Supersonic Heterodyne Receiver

Superhet Radio Block Diagram

The superhet receiver works much better than the simple receiver for the following reasons ...

Superhet disadvantages ...

Superhet Subsystems

Antenna

The antenna will often be a half wave dipole. This is ideal for short wave radio between 1.6MHz and 30 MHz. At lower frequencies a ferrite rod antenna is often used.

Tuning

A simple LC tuned circuit selects the desired radio frequency. The image frequency is generally so different from the wanted frequency that this single stage of tuning is sufficient.

Radio Frequency (RF) Amplifier

This amplifies the radio frequency. If the RF amplifier has a variable gain design, automatic gain control can be applied here.

Local Oscillator

In cheap AM radios, this oscillator is 455kHz higher in frequency than the wanted signal. It could be 455kHz lower but this might cause more unwanted image signal problems.

In FM radios, the local oscillator is 10.7 MHz above the wanted signal.

Mixer

Mixer Example

Intermediate Frequency Amplifier

Intermediate Frequency (IF) Filtering

Demodulator

Sometimes called the Detector.

The audio (or digital data) is separated from the modulated carrier.

Automatic Gain Control

AF Amplifier

Superhet Signals

Superhet Receiver Signals

  1. A wide range of radio frequency signals including the unwanted image signal or second channel.
  2. A much smaller range of radio frequency signals.
    The unwanted image frequency is removed by the tuned circuit. This works well but might not be 100% removed.
    Other frequencies close to the wanted frequency are NOT removed.
  3. An amplified copy of the smaller range of radio frequency signals.
  4. A pure sine wave signal generated by the local oscillator. To tune in different stations, this frequency has to be altered.
  5. The sum and difference frequencies produced by mixing 3 with 4.
    The wanted input frequencies is mixed to become the intermediate frequency.
    The other input frequencies are mixed and fall above or below the intermediate frequency.
  6. The wanted intermediate frequency at a higher signal level. All the other unwanted signals have now been filtered out.
  7. A small audio signal.
  8. A much larger audio signal sufficient to drive the speaker.
  9. A DC voltage proportional to the radio frequency signal strength.
    The DC voltage is fed back and used to reduce the gain of the RF amplifier and IF amplifier.
    It the antenna signal is very strong, the receiver gain is reduced.
    If the antenna signal is weaker, the receiver gain is increased
    This is a closed loop control system. It uses negative feedback.
    It measures the IF output signal strength and alters the receiver gain to keep this signal strength constant.
    The audio level does not increase or decrease if the RF signal gets stronger or weaker.

Satellite TV LNB

Satellite TV is transmitted at a frequency that is so high that low cost co-axial cables can't be used to connect the dish to the receiver. The solution is to use superhet technology. The LNB (low noise block) mounted at the focal point of the dish antenna, uses a local oscillator and mixer to down-convert the satellite frequencies to a much lower frequency. These frequencies can be handled with low cost cables and a relatively simple satellite receiver design.

Audible Heterodynes

To receive Morse code and digital-text with amplitude, frequency or phase modulated signals, the radio frequency is mixed with another locally generated signal to produce an audible heterodyne at about 600 Hz. Without this the Morse would sound like a faint hiss being keyed on and off.

A common and unpleasant cause of interference is unwanted heterodyne signals. These sound like a continuous whistle or whine in the background of the wanted signal. They are caused by carrier waves on a frequency very similar to the wanted frequency. Top quality radio receivers include notch filters to remove the unwanted heterodyne signal.

Circuits

IF Amplifier - Not in the AQA Exam

A Possible IF Amplifier circuit with AGC.

IF Amplifier Circuit

Subject Name     Level     Topic Name     Question Heading     First Name Last Name Class ID     User ID    

fff
Home
<<<
ppw
Pg Up
<<
ppp
Up
<
|||

>|<
nnn
Down
>
nnw
Pg Down
>>
lll
End
>>>

Close
Escape
X

Q: qNum of last_q     Q ID: Question ID         Score: num correct/num attempts         Date Done    

 

Submit
Enter

 

Question Text

image url

 


Help Link

Add     Delete     Clone     Edit     Hardness

Help Text
Debug


 

 

 

Contact, Copyright, Cookies and Legalities: C Neil Bauers - reviseOmatic V4 - © 2016/17

Hosted at linode.com - London