General Licensing Class

Coax Cable

Lake Area Radio KlubSpring 2012

2

Amateur Radio General ClassElement 3 Course Presentation

ELEMENT 3 SUB-ELEMENTS (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 ClassElement 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 Antennas17 - Coax Cable• 18 -RF & Electrical Safety

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 feed-point 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)

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)

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)

50 / 25 2:1 VSWRSWR = Z1 / Z2

SWR = Z1 / Z2 200/ 50 4:1 VSWR

SWR = Z1 / Z250/ 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.

If you feed an antenna that has a 300-ohm feed-point impedance with 50-ohm coaxial cable, the SWR will be 6:1. (G9A13)

Antenna tuner with built in dual needle SWR meter

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 PL-259 connector is commonly used for RF service at frequencies up to 150 MHz. (G6C13)

A high quality SMA connector is useable to 18 GHz and beyond

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 CableValid 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 non- reactive 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 What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non- reactive load having a 200-ohm impedance?

A. 4:1

B. 1:4

C. 2:1

D. 1:2

G9A10 What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non- reactive load having a 10-ohm impedance?

A. 2:1

B. 50:1

C. 1:5

D. 5:1

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

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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