General Licensing Class
Coax Cable
Lake Area Radio Klub
Spring 2012
Amateur Radio General Class
Element 3 Course Presentation
 ELEMENT 3 SUB-ELEMENTS
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(Groupings)
1 - Your Passing CSCE
2 - Your New General Bands
3 - FCC Rules
4 - Be a VE
5 - Voice Operations
6 - CW Lives
7 - Digital Operating
8 - In An Emergency
9 - Skywave Excitement
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Amateur Radio General Class
Element 3 Course Presentation
 ELEMENT 3 SUB-ELEMENTS
(Groupings)
• 10 - Your HF Transmitter
• 11 - Your Receiver
• 12 - Oscillators & Components
• 13 - Electrical Principles
• 14 - Circuits
• 15 - Good Grounds
• 16 - HF Antennas
 17 - Coax Cable
• 18 -RF & Electrical Safety
3
Coax Cable
 50 and 75 ohms are the typical characteristic impedances of coaxial
cables used for antenna feed lines at amateur stations. (G9A02)
 The attenuation of coaxial cable increases as the frequency of the
signal it is carrying increases. (G9A05)
 RF feed line losses usually expressed in dB per 100 ft. (G9A06)
Coax Cable
Coax Cable
 The percentage of power loss that would result from a transmission line
loss of 1 dB would be approx. 20.5 %. (G5B10)
 300 ohms is the characteristic impedance of flat ribbon TV type
twinlead. (G9A03)
 The distance between the centers of the conductors and the radius
of the conductors determine the characteristic impedance of a parallel
conductor antenna feed line. (G9A01)
300 Ohm Twin Lead
Air Dielectric Coaxial Cable
Parallel two-wire line
Coax Cable
 To prevent standing waves on an antenna feed line, the antenna
feed-point impedance must be matched to the characteristic
impedance of the feed line. (G9A07)
 A difference between feed-line impedance and antenna feedpoint impedance is the reason for the occurrence of reflected power
at the point where a feed line connects to an antenna. (G9A04)
 Standing wave ratio can also be determined with a directional
wattmeter. (G4B10)
Coax Cable
 A standing wave ratio of 1:1 will result from the connection of a 50-ohm
feed line to a non-reactive load having a 50-ohm impedance. (G9A11)
SWR = Z1 / Z2
50 / 50
1 : 1 VSWR
Coax Cable
 If you feed a vertical antenna that has a 25-ohm feed-point
impedance with 50-ohm coaxial cable, the SWR will be 2:1. (G9A12)
SWR = Z1 / Z2
50 / 25
2:1 VSWR
 A 4:1 standing wave ratio will result from the connection of a 50-ohm
feed line to a non-reactive load having a 200-ohm impedance. (G9A09)
SWR = Z1 / Z2
200/ 50
4:1 VSWR
 A standing wave ratio of 5:1 will result from the connection of a 50-ohm
feed line to a non-reactive load having a 10-ohm impedance. (G9A10)
SWR = Z1 / Z2
50/ 10
5:1 VSWR
Coax Cable
 If the SWR on an antenna feed line is 5 to 1, and a matching network at the
transmitter end of the feed line is adjusted to 1 to 1 SWR, the resulting
SWR on the feed line is still 5 to 1. (G9A08)
• The antenna tuner allows the transmitter to see a matched impedance
• This delivers full power.
• It does not change the antenna or feedline impedance on its output.
Antenna tuner
with built in
dual needle
SWR meter
 If you feed an antenna that has a 300-ohm feed-point impedance with 50ohm coaxial cable, the SWR will be 6:1. (G9A13)
SWR = Z1 / Z2
300/ 50
6:1 VSWR
Coax Cable
 The type-N connector is a moisture-resistant RF connector useful
to 10 GHz. (G6C16)
Type-N
Type-N
Coax Cable
 The SMA connector is a small threaded connector suitable for
signals up to several GHz. (G6C18)
A high quality SMA connector is useable to 18 GHz and beyond
 A PL-259 connector is commonly used for RF service at frequencies
up to 150 MHz. (G6C13)
Male PL-259
PL-259 T-Connector
Coax Cable
 200 feet is the maximum height above ground to which an antenna
structure may be erected without requiring notification to the FAA
and registration with the FCC, provided it is not at or near a public
use airport. (G1B01)
Maximum
Antenna Height
without FCC
Approval.
200 Ft.
Element 3 General Class Question Pool
Coax Cable
Valid July 1, 2011
Through
June 30, 2015
G9A02
What are the typical characteristic impedances of
coaxial cables used for antenna feed lines at
amateur stations?
A. 25 and 30 ohms
B. 50 and 75 ohms
C. 80 and 100 ohms
D. 500 and 750 ohms
G9A05
How does the attenuation of coaxial cable
change as the frequency of the signal it is
carrying increases?
A. It is independent of frequency
B. It increases
C. It decreases
D. It reaches a maximum at approximately 18 MHz
G9A06 In what values are RF feed line
losses usually expressed?
A. Ohms per 1000 ft
B. dB per 1000 ft
C. Ohms per 100 ft
D. dB per 100 ft
G5B10 What percentage of power loss
would
result from a
transmission line loss of 1 dB?
A. 10.9 %
B. 12.2 %
C. 20.5 %
D. 25.9 %
G9A03 What is the characteristic
impedance of
flat ribbon TV
type twinlead?
A. 50 ohms
B. 75 ohms
C. 100 ohms
D. 300 ohms
G9A01
Which of the following factors determine the
characteristic impedance of a parallel
conductor antenna feed line?
A. The distance between the centers of the conductors and
the radius of the conductors
B. The distance between the centers of the conductors and
the length of the line
C. The radius of the conductors and the frequency of the
signal
D. The frequency of the signal and the length of the line
G9A07 What must be done to prevent
standing
waves on an antenna
feed line?
A. The antenna feed point must be at DC ground
potential
B. The feedline must be cut to an odd number of
electrical quarter wavelengths long
C. The feedline must be cut to an even number of
physical half wavelengths long
D. The antenna feed point impedance must be matched
to the characteristic impedance of the feed line
G9A04
What is the reason for the occurrence of
reflected power at the point where a feedline
connects to an antenna?
A. Operating an antenna at its resonant frequency
B. Using more transmitter power than the antenna can
handle
C. A difference between feed line impedance and antenna
feed point impedance
D. Feeding the antenna with unbalanced feedline
G4B10 Which of the following can be
measured
with a directional
wattmeter?
A. Standing Wave Ratio
B. Antenna front-to-back ratio
C. RF interference
D. Radio wave propagation
G9A11
What standing-wave-ratio will result from the
connection of a 50-ohm feed line to a nonreactive load having a 50-ohm impedance?
A. 2:1
B. 1:1
C. 50:50
D. 0:0
G9A12
What would be the SWR if you feed a vertical
antenna that has a 25-ohm feed-point
impedance with 50-ohm coaxial cable?
A. 2:1
B. 2.5:1
C. 1.25:1
D. You cannot determine SWR from impedance values
G9A09
A. 4:1
B. 1:4
C. 2:1
D. 1:2
What standing-wave-ratio will result from the
connection of a 50-ohm feed line to a nonreactive load having a 200-ohm impedance?
G9A10
A. 2:1
B. 50:1
C. 1:5
D. 5:1
What standing-wave-ratio will result from the
connection of a 50-ohm feed line to a nonreactive load having a 10-ohm impedance?
G9A08
If the SWR on an antenna feedline is 5 to 1, and a matching
network at the transmitter end of the feedline is adjusted
to 1 to 1 SWR, what is the resulting SWR on the feedline?
A. 1 to 1
B. 5 to 1
C. Between 1 to 1 and 5 to 1 depending on the characteristic
impedance of the line
D. Between 1 to 1 and 5 to 1 depending on the reflected
power at the transmitter
G9A13
What would be the SWR if you feed a folded
dipole antenna that has a 300-ohm feed-point
impedance with 50-ohm coaxial cable?
A. 1.5:1
B. 3:1
C. 6:1
D. You cannot determine SWR from impedance values
G6C16 Which of the following describes a
Type-N connector?
A. A moisture-resistant RF connector useful to 10 GHz
B. A small bayonet connector used for data circuits
C. A threaded connector used for hydraulic systems
D. An audio connector used in surround-sound installations
G6C18 What is a type of SMA
connector?
A. A large bayonet-type connector usable at power levels
in excess of 1 KW.
B. A small threaded connector suitable for signals up to
several GHz.
C. A connector designed for serial multiple access signals.
D. A type of push-on connector intended for high-voltage
applications.
G6C13 Which of these connector types
is
commonly used for RF
service at
frequencies
up to 150 MHz?
A. Octal
B. RJ-11
C. PL-259
D. DB-25
G1B01
What is the maximum height above ground to which an
antenna structure may be erected without requiring notification to the FAA and
registration with the FCC, provided it is not at or near a public-use airport?
A. 50 feet
B. 100 feet
C. 200 feet
D. 300 feet
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