GeneralG9D11
Which of the following is a disadvantage of multiband antennas?
D
Answer
Antennas and feed lines
Type
A
They present low impedance on all design frequencies
B
They must be used with an antenna tuner
C
They must be fed with open wire line
D
They have poor harmonic rejection
Answer Notes
Multiband antennas are designed to resonate on multiple frequency bands, which are often harmonically related (e.g., 7 MHz, 14 MHz, 21 MHz). Because they naturally accept signals at these harmonic frequencies, they do not efficiently filter out unwanted harmonic emissions generated by the transmitter.
If a transmitter emits spurious harmonics, the multiband antenna will readily radiate them into the air rather than rejecting them, potentially causing harmful interference to other stations. Conversely, single-band antennas offer a degree of natural filtering because they present a high impedance to out-of-band harmonic frequencies.
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In which direction or directions does an electrically small loop (less than 1/10 wavelength in circumference) have nulls in its radiation pattern?
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What is the common name of a dipole with a single central support?