

Homework 6  AM Reception
Problem 1.
Determine the intermediate frequency bandwidth necessary to achieve a bandwidth
improvement of 16dB for a radio receiver with a radio frequency bandwidth of 320kHz.
{ Solution }
Problem 2.
Determine the improvement in the noise figure for a receiver with an RF
bandwidth equal to 40kHz and an IF bandwidth of 16kHz.
{ Solution }
Problem 3.
Calculate the equivalent noise temperature for an amplifier with a noise
figure of 6dB and an environmental temperature T = 27 deg C.
{ Solution }
Problem 4.
For an amplitude modulated commercial broadcast band receiver with an input filter
Q factor of 85, determine the bandwidth at the low and high ends of the RF spectrum.
{ Solution }
Problem 5.
For an AM super heterodyne receiver using high side injection with a local
oscillator frequency of 1200kHz, determine the IF carrier and upper and lower
side frequencies for an RF envelope that is made up of a carrier and upper
and lower side frequencies of 600kHz, 604kHz, and 596kHz.
{ Solution }
Problem 6.
For a receiver with a plus or minus 2.5kHz tracking error, a 455kHz IF, and a
maximum modulating signal frequency of 6kHz, determine the maximum IF bandwidth.
{ Solution }
Problem 7.
For a receiver with an intermediate frequency, radio frequency, and local oscillator
frequencies of 455kHz, 900kHz, and 1355kHz, determine (a) the image frequency,
(b) IFRR for a pre selector Q of 80.
{ Solution }
Problem 8.
For a citizens band (CB) receiver using high side injection with an RF carrier
of 27.04MHz and a 10.645MHz first IF, determine (a) the local oscillator
frequency, and (b) the image frequency.
{ Solution }
Problem 9.
For a three stage double tuned RF amplifier with an RF carrier equal to 800kHz
and a coefficient of coupling equal to 0.025, determine (a) the bandwidth for
each individual stage, and (b) the overall bandwidth for the three stages.
{ Solution }
Problem 10.
Determine the maximum modulating signal frequency for a peak detector with the
following specifications; C = 1000pF, R = 10k ohms, and m = 0.5. Repeat the
problem for m = 0.707.
{ Solution }
Problem 15.
For an RF receiver with a plus or minus 2800Hz tracking error and a maximum
modulating signal frequency of 4kHz, calculate the minimum IF bandwidth.
{ Solution }
Problem 17.
For a CB receiver using high side injection with an RF carrier of 27.04MHz and
a 10.645MHz IF, find the (a) local oscillator (LO) frequency, and (b) the image frequency.
{ Solution }
Problem 21.
Determine the net receiver gain for an amplitude modulated receiver with the following gains and losses. Gains: RF amplifier = 30dB, IF amplifier = 44dB, audio amplifier = 24dB.
Losses: Preselector loss = 2dB, mixer loss = 6dB, and detector loss = 8dB.
{ Solution }
Engineering key words: Receiver gain, power, amplitude modulation, AM, reception,
loss, intermediate frequency, IF, RF, oscillator, mixer, signal detection, image
frequency, LO, peak signal, doubly tuned, carrier, bandwidth, low side injection,
high side injection, preselector, super heterodyne, noise figure, temperature,
signal broadcast.
