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In which of these conditions would twin feeder be a better choice than coaxial cable
When connecting a multiband doublet to a transmitter
When connecting a 50 Ohm centre fed dipole to a transmitter
When connecting a mobile transmitter to short vertical on the car of the roof
When a section of feeder is to be buried
Twin feeder normally has a an impedance in the range:
1 to 10 Ohms
10 to 100 Ohms
75 to 600 Ohms
600 Ohms to 6000 Ohms
In twin feeder:
current flows in one wire and the other wire is at earth potential
the same current flows in each wire reinforcing the output at the antenna end of the feeder
equal and opposite currents flow in each wire cancelling each other
all points of the feeder are at the same potential when feeding a non-resonant antenna
In correctly connected coaxial cable the RF
field only exists within the braid of the coax
field only exists within the cable
can be disrupted by metal objects outside of the coax
current is not attenuated by the coax
A length of coaxial feeder has a loss of 6dB. If a transmitter has an RF output of 40 watts, how much will be radiated from the antenna?