OK, we're going to start on EMC with some questions from the QADV program:
If a TV picture contains a 'ghost' in the form of a faint image of the same picture displaced to the right, this CANNOT be caused by
a) large buildings
c) tower cranes
d) transmissions by radio amateurs
The answer is d) transmissions by radio amateurs. (By the way the image is known as "Ghosting").
In amateur radio, a low-pass r.f. filter is used to
a) decrease the impedance of an antenna
b) suppress harmonics
c) increase audio intelligibility
d) remove intermodulation products
The correct answer is b) suppress harmonics.
Which one of these actions would reduce breakthrough from a radio transmission onto a TV?
a) Use a speech processor in the transceiver
b) Lower the height of the transmitting antenna
c) Move the transmitting antenna away from the TV
d) Operate using SSB exclusively.
The answer is c) Move the transmitting antenna away from the TV.
Remember that d) is incorrect because SSB is more likely to cause breakthrough than AM or FM.
Which of the following should be fitted in the downlead of a TV antenna to prevent breakthrough from a 2 metre amateur signal?
a) Band-stop filter
b) Mains filter
c) Low-pass filter
d) Balun transformer
The correct answer is a) Band-stop filter.
The occurrence known as the "rusty bolt effect" results in
a) image breakthrough onto the i.f. of a receiver
b) 'ghosting' on analogue TV signals
c) an increase in the maximum usable frequency (MUF)
d) the generation of passive intermodulation products
The answer is d) the generation of passive intermodulation products.
Which one of the following helps to prevent the second harmonic of a transmission being radiated?
a) A key-click filter
b) An output stage with valves or transistors in push-pull
c) A vertical antenna
d) A screened mains lead to the transceiver.
The correct answer is b) An output stage with valves or transistors in push-pull.
To avoid EMC problems, the transmitting antenna should NOT be
a) mounted high up
c) connected directly to the transceiver
d) located at a distance from the house
The correct answer is c) connected directly to the transceiver.
The gain of a receiver is being affected by a strong s.s.b. signal on another frequency. This effect is called
a) cross modulation
b) image pick-up
The correct answer is a) cross-modulation.